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Hands-on dissections using cadaveric tissues for neuroanatomical education are not easily available in many educational institutions due to financial, safety, and ethical factors. Supplementary pedagogical tools, for instance, 3D models of anatomical specimens acquired with photogrammetry are an efficient alternative to democratize the 3D anatomical data. The aim of this study was to describe a technical guideline for acquiring realistic 3D anatomic models with photogrammetry and to improve the teaching and learning process in neuroanatomy. Seven specimens with different sizes, cadaveric tissues, and textures were used to demonstrate the step-by-step instructions for specimen preparation, photogrammetry setup, post-processing, and display of the 3D model. The photogrammetry scanning consists of three cameras arranged vertically facing the specimen to be scanned. In order to optimize the scanning process and the acquisition of optimal images, high-quality 3D models require complex and challenging adjustments in the positioning of the specimens within the scanner, as well as adjustments of the turntable, custom specimen holders, cameras, lighting, computer hardware, and its software. MeshLab® software was used for editing the 3D model before exporting it to MedReality® (Thyng, Chicago, IL) and SketchFab® (Epic, Cary, NC) platforms. Both allow manipulation of the models using various angles and magnifications and are easily accessed using mobile, immersive, and personal computer devices free of charge for viewers. Photogrammetry scans offer a 360° view of the 3D models ubiquitously accessible on any device independent of operating system and should be considered as a tool to optimize and democratize the teaching of neuroanatomy.

Protection of photosystem II against damage from excess light by nonphotochemical quenching (NPQ) includes responses on a wide range of timescales. The onset of the various phases of NPQ overlap in time making it difficult to discern if they influence each other or involve different photophysical mechanisms. To unravel the complex relationship of the known actors in NPQ, we perform fluorescence lifetime snapshot measurements throughout multiple cycles of alternating 2 min periods of high light and darkness. By comparing the data with an empirically based mathematical model that describes both fast and slow quenching responses, we suggest that the rapidly reversible quenching response depends on the state of the slower response. By studying a series of Arabidopsis thaliana mutants, we find that removing zeaxanthin (Zea) or enhancing PsbS concentration, for example, influences the amplitudes of the slow quenching induction and recovery, but not the timescales. The plants' immediate response to high light appears independent of the illumination history, while PsbS and Zea have distinct roles in both quenching and recovery. We further identify two parameters in our model that predominately influence the recovery amplitude and propose that our approach may prove useful for screening new mutants or overexpressors with enhanced biomass yields under field conditions.

The rapid response of photosynthetic organisms to fluctuations in ambient light intensity is incompletely understood at both the molecular and membrane levels. In this review, we describe research from our group over a 10-year period aimed at identifying the photophysical mechanisms used by plants, algae and mosses to control the efficiency of light harvesting by photosystem II on the seconds-to-minutes time scale. To complement the spectroscopic data, we describe three models capable of describing the measured response at a quantitative level. The review attempts to provide an integrated view that has emerged from our work, and briefly looks forward to future experimental and modelling efforts that will refine and expand our understanding of a process that significantly influences crop yields.

In photosynthesis, solar energy is absorbed and converted into chemical energy. Chlorophyll embedded in proteins absorb light and transfer excitation energy to reaction centers where charge separation occurs. However, the solar flux incident on photosynthetic organisms is highly variable, requiring complex feedback systems to regulate the excitation pressure on reaction centers and prevent excess absorbed energy from causing damage. During periods of transient high light, excess absorbed energy is dissipated as heat. This is routinely observed as the quenching of chlorophyll fluorescence, and often broadly referred to as non-photochemical quenching (NPQ). Understanding the mechanisms through which photosynthetic systems dissipate excess energy and regulate excitation pressure in response to variable light conditions requires extensive quantitative modeling of the photosynthetic system and energy dissipation to interpret experimental observations. This review discusses efforts to model energy dissipation, or quenching, in Arabidopsis thaliana and their connections to models of regulatory systems that control quenching. We begin with a review of theory used to describe energy transfer and experimental data obtained to construct energy transfer models of the photosynthetic antenna system that underlie the interpretation of chlorophyll fluorescence quenching. Second, experimental evidence leading to proposed molecular mechanisms of quenching and the implications for modeling are discussed. The initial incorporation of depictions of proposed mechanisms into quantitative energy transfer models is reviewed. Finally, the necessity of connecting energy transfer models that include molecular models of quenching mechanisms with regulatory models is discussed.

Nonphotochemical quenching (NPQ) provides an essential photoprotection in plants, assuring safe dissipation of excess energy as heat under high light. Although excitation energy transfer (EET) between chlorophyll (Chl) and carotenoid (Car) molecules plays an important role in NPQ, detailed information on the EET quenching mechanism under in vivo conditions, including the triggering mechanism and activation dynamics, is very limited. Here, we observed EET between the Chl Q y state and the Car S1 state in high-light-exposed spinach thylakoid membranes. The kinetic and spectral analyses using transient absorption (TA) spectroscopy revealed that the Car S1 excited state absorption (ESA) signal after Chl excitation has a maximum absorption peak around 540 nm and a lifetime of ∼8 ps. Snapshot TA spectroscopy at multiple time delays allowed us to track the Car S1 ESA signal as the thylakoid membranes were exposed to various light conditions. The obtained snapshots indicate that maximum Car S1 ESA signal quickly rose and slightly dropped during the initial high-light exposure (

Photosynthetic organisms use various photoprotective mechanisms to dissipate excess photoexcitation as heat in a process called nonphotochemical quenching (NPQ). Regulation of NPQ allows for a rapid response to changes in light intensity and in vascular plants, is primarily triggered by a pH gradient across the thylakoid membrane (∆pH). The response is mediated by the PsbS protein and various xanthophylls. Time-correlated single-photon counting (TCSPC) measurements were performed on Arabidopsis thaliana to quantify the dependence of the response of NPQ to changes in light intensity on the presence and accumulation of zeaxanthin and lutein. Measurements were performed on WT and mutant plants deficient in one or both of the xanthophylls as well as a transgenic line that accumulates lutein via an engineered lutein epoxide cycle. Changes in the response of NPQ to light acclimation in WT and mutant plants were observed between two successive light acclimation cycles, suggesting that the character of the rapid and reversible response of NPQ in fully dark-acclimated plants is substantially different from in conditions plants are likely to experience caused by changes in light intensity during daylight. Mathematical models of the response of zeaxanthin- and lutein-dependent reversible NPQ were constructed that accurately describe the observed differences between the light acclimation periods. Finally, the WT response of NPQ was reconstructed from isolated components present in mutant plants with a single common scaling factor, which enabled deconvolution of the relative contributions of zeaxanthin- and lutein-dependent NPQ.

The 3D stereoscopic technique consists in providing the illusional perception of depth of a given object using two different images mimicking how the right and left eyes capture the object. Both images are slightly different and when overlapped gives a three‐dimensional (3D) experience. Considering the limitations for establishing surgical laboratories and dissections courses in some educational institutions, techniques such as stereoscopy and photogrammetry seem to play an important role in neuroanatomy and neurosurgical education. The aim of this study was to describe how to combine and set up realistic models acquired with photogrammetry scans in 3D stereoscopic projections. Three donors, one dry skull, embalmed brain and head, were scanned using photogrammetry. The software used for displaying the final realistic 3D models (Blender, Amsterdam, the Netherlands) is a free software and allows stereoscopic projection without compromising the interactivity of each model. By default, the model was exported and immediately displayed as a red cyan 3D mode. The 3D projector used in the manuscript required a side‐by‐side 3D mode which was set up with simple commands on the software. The final stereoscopy projection offered depth perception and a visualization in 360° of each donor; this perception was noted especially when visualizing donors with different cavities and fossae. The combination of 3D techniques is of paramount importance for neuroanatomy education. Stereoscopic projections could provide a valuable tool for neuroanatomy instruction directed at clinical trainees and could be especially useful when access to laboratory‐based learning is limited. [ABSTRACT FROM AUTHOR]