The lack of oxygen (O2) causes changes in the cell functioning. Modeling hypoxic conditions in vitro is challenging given that different cell types exhibit different sensitivities to tissue O2 levels. We present an effective in vivo platform for assessing various tissue and organ parameters in Danio rerio larvae under acute hypoxic conditions. Our system allows simultaneous positioning of multiple individuals within a chamber where O2 level in the water can be precisely and promptly regulated, all while conducting microscopy. We applied this approach in combination with a genetically encoded pH-biosensor SypHer3s and a highly H2O2-sensitive Hyper7 biosensor. Hypoxia causes H2O2 production in areas of brain, heart and skeletal muscles, exclusively in the mitochondrial matrix; it is noteworthy that H2O2 does not penetrate into the cytosol and is neutralized in the matrix upon reoxygenation. Hypoxia causes pronounced tissue acidosis, expressed by a decrease in pH by 0.4-0.6 units everywhere. Using imaging photoplethysmography, we measured in D.rerio fry real-time heart rate decrease under conditions of hypoxia and subsequent reoxygenation. Our observations in this experimental system lead to the hypothesis that mitochondria are the only source of H2O2 in cells of D.rerio under hypoxia.

Extremely low-frequency magnetic fields (ELF-MF) up to 100 μT exhibit impacts on physiological processes, including heart function. The mechanisms underlying the influence of these fields on fish heart rates remain insufficiently explored. We assumed that the direct impact of ELF-MF with a frequency close to the heart rate could entrain oscillatory processes responsible for autonomously maintaining heart rhythm in zebrafish embryos. Embryos' heart rates ranged from 1.44 to 3 Hz depending on age, and ELF-MF with frequencies precisely matched, 10% higher, or lower than the heart rate were applied. Additionally, embryos experienced ELF-MF with amplitudes varying by an order of magnitude. Almost all tested ELF-MF induced an increased heart rate effect. This effect was the most pronounced when the exposure occurred earlier during ontogenesis. Fields with frequencies close to the heart rate did not entrain cardiac contractions in zebrafish embryos. A significant negative correlation between heart rate increase and ELF-MF frequency was observed for ELF-MF with amplitudes of 1.98–3.2 μT and 46.8 μT but not 30 μT. Probable molecular mechanisms underlying these effects are discussed in terms of magnetic influence on radical pairs within biochemical oscillating processes.

Remote mapping of chlorophyll concentration in leaves is highly important for various biological and agricultural applications. Multiple spectral indices calculated from reflectance at specific wavelengths have been introduced for chlorophyll content quantification. Depending on the crop, environmental factors and task, indices differ. To map them and define the most accurate index, a single multi-spectral imaging system with a limited number of spectral channels is insufficient. When the best chlorophyll index for a particular task is unknown, hyperspectral imager able to collect images at any wavelengths and map multiple indices is in need. Due to precise, fast and arbitrary spectral tuning, acousto-optic imagers provide highly optimized data acquisition and processing. In this study, we demonstrate the feasibility to extract the distribution of chlorophyll content from acousto-optic hyperspectral data cubes. We collected spectral images of soybean leaves of 5 cultivars in the range 450–850 nm, calculated 14 different chlorophyll indices, evaluated absolute value of chlorophyll concentration from each of them via linear regression and compared it with the results of well-established spectrophotometric measurements. We calculated parameters of the chlorophyll content estimation models via linear regression of the experimental data and found that index CI_RE demonstrates the highest coefficient of determination 0.993 and the lowest chlorophyll content root-mean-square error 0.66 μg/cm². Using this index and optimized model, we mapped chlorophyll content distributions in all inspected cultivars. This study exhibits high potential of acousto-optic hyperspectral imagery for mapping spectral indices and choosing the optimal ones with respect to specific crop and environmental conditions.

Identification of specific vascular patterns in skin formations is important for non-invasive differential diagnosis of benign and malignant tissues. Accurate blood vessel mapping and quantitative analysis of the vessels morphology may increase the diagnostic efficiency significantly in comparison to conventional dermatoscopy methods. In this paper, we propose videocapillaroscopy technique for non-invasive visualization of microvascular architecture right in the nevi area. It includes acquisition of skin lesion images by exoscope-based imaging system and their digital processing including non-uniformity correction, local and global stabilization, detection and quantification of vessels, comparison of the obtained vessel maps with the reference data. We have demonstrated the efficiency of microvascular network visualization in various melanocytic skin formations. Proposed technique may complement conventional dermatoscopy for diagnosing skin lesions and become especially effective in the early stages of diseases.