Biology subjects

Woods, A. L.

Publications and source records attributed to Woods, A. L..

3 recordsLinked to original sources

bioRxiv2024

Non-Degenerate Two-Photon Imaging of Deep Rodent Cortex using Indocyanine Green in the water absorption window

We present a novel approach for deep vascular imaging in rodent cortex at excitation wavelengths susceptible to water absorption using two-photon microscopy with photons of dissimilar wavelengths. We demonstrate that non-degenerate two-photon excitation (ND-2PE) enables imaging in the water absorption window from 1400-1550 nm using two synchronized excitation sources at 1300 nm and 1600 nm that straddle the absorption window. We explore the brightness spectra of indocyanine green (ICG) and assess its suitability for imaging in the water absorption window. Further, we demonstrate in vivo imaging of the rodent cortex vascular structure up to 1.2 mm using ND-2PE. Lastly, a comparative analysis of ND-2PE at 1435 nm and single-wavelength, two-photon imaging at 1300 nm and 1435 nm is presented. Our work extends the excitation range for fluorescent dyes to include water absorption regimes and underscores the feasibility of deep two-photon imaging at these wavelengths.

neuroscience↗

bioRxiv2023

Pulse train gating to improve signal generation for in vivo two-photon fluorescence microscopy

SignificanceTwo-photon microscopy is used routinely for in vivo imaging of neural and vascular structure and function in rodents with a high resolution. Image quality, however, often degrades in deeper portions of the cerebral cortex. Strategies to improve deep imaging are therefore needed. We introduce such a strategy using gates of high repetition rate ultrafast pulse trains to increase signal level. AimWe investigate how signal generation, signal-to-noise ratio (SNR), and signal-to-background ratio (SBR) improve with pulse gating while imaging in vivo mouse cerebral vasculature. ApproachAn electro-optic modulator is used with a high-power (6 W) 80 MHz repetition rate ytterbium fiber amplifier to create gates of pulses at a 1 MHz repetition rate. We first measure signal generation from a Texas Red solution in a cuvette to characterize the system with no gating and at a 50%, 25%, and 12.5% duty cycle. We then compare signal generation, SNR, and SBR when imaging Texas Red-labeled vasculature using these conditions. ResultsWe find up to a 6.73-fold increase in fluorescent signal from a cuvette when using a 12.5% duty cycle pulse gating excitation pattern as opposed to a constant 80 MHz pulse train. We verify similar increases for in vivo imaging to that observed in cuvette testing. For deep imaging we find pulse gating to result in a 2.95-fold increase in SNR and a 1.37-fold increase in SBR on average when imaging mouse cortical vasculature at depths ranging from 950 m to 1050 m. ConclusionsWe demonstrate that a pulse gating strategy can either be used to limit heating when imaging superficial brain regions or used to increase signal generation in deep regions. These findings should encourage others to adopt similar pulse gating excitation schemes for imaging neural structure through two-photon microscopy.

neuroscience↗

bioRxiv2017

The BMP2/4 ortholog Dpp functions as an inter-organ signal that regulates developmental timing in Drosophila

For many organisms, developmental transitions are triggered by a neuroendocrine axis and are contingent upon multiple organs achieving sufficient growth and maturation. How the status of peripheral organs is communicated to the neuroendocrine axis is not known. In Drosophila larvae, metamorphosis is triggered by the steroid hormone ecdysone, secreted by the prothoracic gland (PG). Here we show that the BMP2/4 ortholog Dpp, which regulates growth and patterning of larval imaginal discs, also functions as a systemic signal to regulate developmental timing. Dpp from peripheral tissues, mostly imaginal discs, can reach the PG and inhibit ecdysone biosynthesis. As the discs grow, Dpp signaling decreases in the PG, thus alleviating the inhibition of ecdysone biosynthesis, and permitting entry into metamorphosis. We suggest that if a tissue can trap more morphogen locally as it grows and matures, then circulating levels of morphogen can provide a systemic readout of organ size and maturation.\n\nOne Sentence SummaryDpp functions as a long-range endocrine signal between peripheral tissues and the prothoracic gland to regulate developmental timing in Drosophila.

developmental biology↗