Non-staining visualization of embryogenesis and energy metabolism in medaka fish eggs using near-infrared spectroscopy and imaging

Abstract

The energy metabolism and embryogenesis of fertilized Japanese medaka eggs were investigated in vivo at the molecular level using near-infrared (NIR) spectroscopy and imaging. Changes in chemical components, such as proteins and lipids, in yolk sphere and embryonic body were studied over the course of embryonic development. Metabolic changes that represent variations in the concentrations and molecular compositions of proteins and lipids in the yolk part, particularly on the 1 day after fertilization and the day just before hatching, were successfully identified in the 4900-4000 cm wavenumber region. The yolk components were shown to have specific functions at the very early and final stages of the embryonic development. Proteins with α-helix- or β-sheet-rich structures clearly showed the different variation patterns within the developing egg. Furthermore, the distribution of lipids could be selectively visualized using data from the higher wavenumber region. Detailed embryonic structures were clearly depicted in the NIR images using the data from the 6400-5500 cm region in which the embryo parts had some characteristic peaks due to unsaturated fatty acids. It was made clear that yolk and embryo parts had different components especially lipid components. The present study provides new insights into material variations in the fertilized egg during its growth. NIR imaging proved to be valuable in investigating the embryogenesis in vivo at the molecular level in terms of changes in biomolecular concentrations and compositions, metabolic differentiation, and detailed information about embryonic structures without the need for staining.

Breakthrough Potential in Near-Infrared Spectroscopy: Spectra Simulation. A Review of Recent Developments

“…Fatty acids manifest various properties interesting from the point of view of physical chemistry, e.g., association mechanisms and hydrogen bonding properties (Iwahashi et al, 1995a,b; Matsuzawa et al, 2013). These systems are also extremely important in applied NIR studies involving any kind of biological samples, e.g., in hyperspectral imaging and analytical applications (Ishigaki et al, 2016a,b; Puangchit et al, 2017). For these reasons, SCFAs and MCFAs were examined by Grabska et al in their two following studies (Grabska et al, 2017c,d).…”

“…Further expansion onto more complex objects (e.g., LCFAs, lipids, proteins, nucleic acids) may be anticipated in the foreseeable future. So far, the reported accomplishments in theoretical NIRS of small biomolecules were successfully employed for the interpretation of NIR images of biosamples (Puangchit et al, 2017).…”

“…The quality of simulation allowed for unambiguous assignment of all NIR bands and also to differentiate clearly between saturated and unsaturated LCFAs. Further progress in this field is strongly promoted as it finds immediate application in NIR biospectroscopy and imaging (Grabska et al, 2017c,d; Puangchit et al, 2017).…”

Quantum mechanical simulations of near-infrared spectra of biomolecules – Long-chain fatty acids

“…Further observations and the resulting conclusions have been discussed in detail in the original report. 9 A good example of how such information can be used in applied biochemical studies has recently been provided by Puangchit et al 14 and Ishigaki et al 15 in their investigation of the medaka fish eggs and embryos by NIR imaging, due to the correspondence between the fertility of an egg and the distribution of fatty acids within it. The NIR simulations of smaller sized fatty acids (SCFAs 16 and MCFAs 17 ) have been used already in such cases.…”

“…In example, unambiguous identification of the methyl group vibrations allows for better understanding of the NIR images of biological structures. 14,15 As a separate note, it is necessary to explain the assumed limit of the NIR modes to be simulated. Due to practical limits in the workstation memory which is available for computation, in the reported simulations only binary combination and first overtone modes have been included.…”