Blue Light Pulses Research Articles

Effects of turfgrass canopy shade levels and quantum spectrum on the germination and development of smooth crabgrass (Digitaria ischaemum)

AbstractSmooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.] is one of the most troublesome summer annual weeds in cool‐season turfgrass. Field experiments demonstrated a strong relationship between spring photosynthetic active radiation reaching the soil surface and the resulting smooth crabgrass cover in Kentucky bluegrass (Poa pratensis L.) 2/3 months later in summer. Both smooth crabgrass and canopy penetrating light were consistently reduced by higher mowing heights. Follow‐up experiments in controlled environments were initiated to improve our understanding of how light quality and quantity influence smooth crabgrass germination and growth. Smooth crabgrass germination was ≥99% following exposure to blue, red (R), far red (FR), both R and FR light pulses, or complete darkness treatments. A second germination experiment examined six levels of turfgrass canopy shade (0%, 24%, 44%, 77%, 90%, and 100% photosynthetic photon flux density [PPFD] reduction) and found that smooth crabgrass germination was ≥99% for all treatments. These experiments indicate that light quality and quantity do not affect smooth crabgrass germination. A greenhouse experiment examined five levels of turfgrass canopy shade (0%, 44%, 59%, 81%, and 91% PPFD reduction). Smooth crabgrass quantum and PSII (Photosystem II) operating efficiency increased in response to shade, while leaf number and thickness, specific leaf weight, tillering, mass, electron transport rate, and stomatal conductance decreased with increasing shade. Overall, the results demonstrate that smooth crabgrass is able to germinate regardless of canopy density, but seedling growth, development, and plant function are diminished in a dense turfgrass canopy shade.

Low-Cost, High-Efficiency Aluminum Zinc Oxide Synaptic Transistors: Blue LED Stimulation for Enhanced Neuromorphic Computing Applications.

Neuromorphic devices are electronic devices that mimic the information processing methods of neurons and synapses, enabling them to perform multiple tasks simultaneously with low power consumption and exhibit learning ability. However, their large-scale production and efficient operation remain a challenge. Herein, we fabricated an aluminum-doped zinc oxide (AZO) synaptic transistor via solution-based spin-coating. The transistor is characterized by low production costs and high performance. It demonstrates high responsiveness under UV laser illumination. In addition, it exhibits effective synaptic behaviors under blue LED illumination, indicating high-efficiency operation. The paired-pulse facilitation (PPF) index measured from optical stimulus modulation was 179.6%, indicating strong synaptic connectivity and effective neural communication and processing. Furthermore, by modulating the blue LED light pulse frequency, an excitatory postsynaptic current gain of 4.3 was achieved, demonstrating efficient neuromorphic functionality. This study shows that AZO synaptic transistors are promising candidates for artificial synaptic devices.

Dual color optogenetic tool enables heart arrest, bradycardic, and tachycardic pacing in Drosophila melanogaster

In order to facilitate cardiovascular research to develop non-invasive optical heart pacing methods, we have generated a double-transgenic Drosophila melanogaster (fruit fly) model suitable for optogenetic pacing. We created a fly stock with both excitatory H134R-ChR2 and inhibitory eNpHR2.0 opsin transgenes. Opsins were expressed in the fly heart using the Hand-GAL4 driver. Here we describe Hand > H134R-ChR2; eNpHR2.0 model characterization including bi-directional heart control (activation and inhibition) upon illumination of light with distinct wavelengths. Optical control and real-time visualization of the heart function were achieved non-invasively using an integrated light stimulation and optical coherence microscopy (OCM) system. OCM produced high-speed and high-resolution imaging; simultaneously, the heart function was modulated by blue (470 nm) or red (617 nm) light pulses causing tachycardia, bradycardia and restorable cardiac arrest episodes in the same animal. The irradiance power levels and illumination schedules were optimized to achieve successful non-invasive bi-directional heart pacing in Drosophila larvae and pupae.

Real-time (re)shaping of cardiac action potentials by an opto-electronic feedback control system in the multicellular setting

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Research Council Starting Grant and Consolidator Grant to Daniël A Pijnappels Background The membrane potential (Vm) in cardiomyocytes fulfills essential regulatory roles in various biological functions, including not only action potential (AP) propagation and mechanical contraction, but also homeostatic regulation. In-depth studies into these roles have been severely hampered by the lack of research methods allowing full control over Vm, especially in multicellular cardiac preparations. Purpose We aimed to unlock new research possibilities by the development of an experimental system (APqr) capable of full Vm control, including instantaneous modulation of AP morphology on a multicellular levelin the multicellular setting. Methods Monolayers of immortalized human atrial myocytes (hiAMs, n=7) were genetically modified to express the blue light-activatable cation channel Cheriff and the red light-sensitive inward chloride pump Jaws for depolarizing and re- or hyperpolarizing effects, respectively. Real-time Vm readout was obtained by patch clamp electrophysiology. Deviations of Vm from reference values were calculated by a custom closed-coop controller. A 470-nm and a 617-nm LED were modulated by the controller in a Vm deviation-dependent manner, selectively activating Cheriff or Jaws. Electrical disturbances were introduced by application of 4-aminopyridien (4AP, 200 µM) or a preprogrammed blue-light pulse creating abnormal cation influx during the repolarization phase of the hiAM AP. Results Average AP durations at 90% repolarization (APD90) increased by 82.4 ms following 4AP application and by 362.5 ms in the presence of light-induced abnormal cation influx compared to control conditions. APqr reduced these APD90 differences to 1.9 ms and 4.6 ms on average, with Vm deviations less than 2.5 mV in 74.7% and 94.4% of the time, respectively. APqr could also be applied for the enforcement of arbitrary AP shapes. In these experiments, reference Vm values consisted of APs recorded from hiAM monolayers exposed to drugs with APD-prolonging (4AP) or shortening (carbachol) effects. APqr was able to enforce these reference APs on hiAM monolayers with high accuracy, with Vm deviations less than 2.5 mV in 95.8% and 94.4% of the time, respectively. Conclusions APqr preserves AP morphologies in the presence of electrical perturbations of different origin without any prior knowledge of the disturbance and enforces arbitrary AP morphologies with high accuracy in an immediate and self-regulatory manner. Collectively, these results set the stage for the refinement and application of opto-electronic control systems to enable in-depth investigation into the regulatory roles of the membrane potential in health and disease.

Crosstalk amongst oxytocin and vasopressin synthesizing neurons of the paraventricular nucleus of the hypothalamus increases blood pressure in mice

The paraventricular nucleus of the hypothalamus (PVH) orchestrates neuroendocrine release and autonomic outflow to maintain body fluid homeostasis and cardiovascular function. Emerging evidence supports the notion that neuropeptides synthesized by PVH neurons create paracrine signals that alter physiology and behavior by affecting the activity of neighboring neurons. Here, we test the hypothesis that PVH neurons synthesizing oxytocin (hereafter referred to a PVHOT) create a paracrine signal that regulates blood pressure. Mice with the expression of Cre-recombinase directed to the OT gene were bred that mice that express a CAG-driven LoxP-flanked stop-codon preceding a channelrhodopsin-2 (ChR2) and eYFP fusion gene at the Rosa26 locus. This produced mice expressing only Cre-recombinase (controls) or mice with ChR2-eYFP expression directed to cells that express oxytocin (OT-ChR2). Confocal image analysis found that ~90% of eYFP expressing neurons were also immunolabeled for OT and electrophysiological recordings obtained from these neurons revealed that pulses of blue light elicited the firing of action potentials. These results confirm directed and functional expression of ChR2 within PVHOT. In vivo optogenetic excitation of PVHOT increased blood pressure and decreased heart rate in OT-ChR2 mice relative to controls. Ganglionic blockade with hexamethonium had no effect on the increased blood pressure elicited by optogenetic excitation of PVHOT but it completely abolished the bradycardia that was previously observed. These results suggest that excitation of PVHOT recruits a neuroendocrine signal that promotes vasoconstriction, which elicits the baroreflex to induce bradycardia by engaging the autonomic nervous system. Consistent with this interpretation, optogenetic excitation of PVHOT increased circulating levels of OT; however, the elevated blood pressure persisted after systemic administration of an OT receptor antagonist. Intriguingly, in vitro optogenetic excitation of PVHOT evoked Ca2+ flux in CHO cells expressing OT or vasopressin receptors (V1aR), suggesting that robust firing of PVHOT is followed by local release of OT. Optogenetic excitation of PVHOT augmented firing of neurons of the PVH that synthesize vasopressin and tended to increase circulating levels of this neuropeptide. Remarkably, systemic administration of a V1aR antagonist completely abolished the increase in blood pressure and bradycardia that were previously observed with in vivo optogenetic excitation of PVHOT. Collectively, these results reveal that robust firing of PVHOT creates an oxytocinergic paracrine signal that increases blood pressure by activating V1aR(s) and increasing circulating vasopressin. AHA 23POST1020034 to KE. NHLBI F31HL1162540 to CBH. NHLBI R01HL136595, R35HL150750, R01HL145028 and NCCIH R65AT012142 to ADK & EGK. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Optogenetic Control of Oncogenic Signaling in B-Cell Malignancies

Background: B-cell receptor (BCR) signals are essential determinants of survival and proliferation throughout normal B-cell development. In B-cell malignancies, these signals are frequently generated by oncogenic mimics of the BCR signaling pathway. For instance, oncogenes in B-ALL, derived from B-cell precursors, typically mimic survival signals from a constitutively active pre-BCR, while tonic and chronic active BCR signaling were identified in mature B-cell lymphomas. Oncogenic BCR-signaling represents an important target of therapeutic intervention: for instance, small molecule inhibitors of SYK (e.g. entospletinib) and BTK (e.g. ibrutinib) have been developed to disrupt oncogenic BCR signaling in mature B-cell lymphomas. Besides SYK and BTK tyrosine kinases, oncogenic BCR-signaling leads to activation of PLCG2, which initiates the release of Ca 2+ from the ER into the cytoplasm. Thereby, calcium flux is decoded by NFATC1 or NF-kB based on fast (NFATC1) or slow (NF-kB) frequencies of Ca 2+-signals. Significance: To interrogate Ca 2+-signals as critical integration point of oncogenic BCR-signaling, we engineered cell lines and PDX with a GCaMP6s-biosensor, which allows tracing of calcium signaling in single cells over time ( Figure A). To cover B-cell malignancies from multiple stages of B-cell development, we engineered B-ALL (pro- and pre-B cells), mantle cell lymphoma (MCL, naïve B-cells), Burkitt's lymphoma (germinal center), DLBCL (post-GC), multiple myeloma (terminally differentiated plasma cells) and Hodgkin's disease (“crippled” BCR-deficient GC-B cells). Strikingly, B-cell malignancies exhibit autonomous Ca 2+-oscillations, which decreased in their frequency from 20 mHz (pro- and pre-B), 11 mHz (naïve), 4 mHz (germinal center) to 0 mHz in post-GC and terminally differentiated plasma cells based on the differentiation stage of their cell of origin ( Figure A). Results: Given the striking differences in oncogenic BCR-signaling as measured by autonomous Ca 2+ oscillations, we developed an optogenetic system to control the frequency and amplitude of Ca 2+ oscillations by blue light pulses ( Figure B). To model frequency-modulated Ca 2+ signaling in B-cells, we engineered murine pre-B cells carrying an optogenetic tool termed OptoCRAC, which enables reversible activation and inactivation of the plasma membrane Ca 2+ channel Orai1 by intermittent blue light irradiation. Time-lapse imaging of a fluorescent Ca 2+ reporter (R-CaMP1.07) confirmed rapid and reversible Ca 2+ influx in response to intermittent blue light pulses. To assess the phenotypic consequence of high-frequency Ca 2+ oscillations, we developed an LED-array-based optogenetic platform for cell culture plates. While low-frequency Ca 2+ oscillations (0.5 mHz) did not impact cell viability, high-frequency Ca 2+ oscillations (20 mHz) rapidly induced NFAT activation (5 min), and eventually cell death within 72 h ( Figure B). Mechanism and conclusions: To elucidate the mechanistic contribution of NFATC1 in B-cell death induced by fast Ca 2+ oscillations, we tested whether genetic deletion of Nfatc1 is sufficient to rescue B-cell death upon fast Ca 2+ oscillation induced by 20 mHz intermittent blue light pulses. As expected, while B-ALL cells retaining intact Nfatc1 rapidly decreased cell viability, the cells with Cre-mediated deletion persistently remained in cell culture upon 20 mHz Ca 2+ oscillation. In addition to genetic deletion of Nfatc1, we also found that inducible expression of mutant activators of NF-kB signaling were able to rescue B-cells from cell death induced by high-frequency oscillations: Concurrent expression of Card11 L232LI, MYD88 L265P and IKK2 S177E/S181E not only reduced the frequency of autonomous Ca 2+ oscillations but also enabled B-cell survival despite delivery of light-pulses and Ca 2+ oscillations at a fast 20 mHz frequency. We conclude that autonomous Ca 2+ oscillations represent a critical integration point of oncogenic BCR-signaling in B-cell malignancies and that optogenetic control of BCR-downstream Ca 2+ oscillations will reveal previously unrecognized vulnerabilities that can be exploited to increase efficacy of BCR-signaling inhibitors (e.g. ibrutinib, entospletinib, idelalisib) that are currently being used for the treatment of B-cell lymphomas.

An opto-electronic control system for real-time complete (re)shaping of cardiac action potentials on a multicellular scale

Abstract Background Cardiomyocytes maintain a membrane potential (Vm), which fulfills essential regulatory roles in various biological functions, including not only action potential (AP) propagation and mechanical contraction, but also homeostatic regulation. In-depth studies into these roles have been severely hampered by the lack of research methods allowing full control over Vm, especially in multicellular cardiac preparations. Purpose We aimed to unlock new research possibilities by the development of an experimental system (APqr) capable of full Vm control, including instantaneous modulation of AP morphology on a multicellular level. Methods Immortalized human atrial myocytes (hiAMs) grown in monolayer format (n=7) were genetically modified to express the blue light-activatable cation channel Cheriff and the red light-sensitive inward chloride pump Jaws for depolarizing and hyperpolarizing effects, respectively. Real-time Vm readout was obtained by patch clamp electrophysiology. Dynamic Vm control was achieved by a custom closed-coop controller calculating Vm deviations from reference values. A 470-nm and a 617-nm LED were modulated by the controller in a Vm deviation-dependent manner, selectively activating Cheriff and Jaws. To explore the feasibility of AP restoration, electrical disturbances were introduced by non-selective potassium channel blockade (4-aminopyridine, 4AP, 200 µM) or by a preprogrammed blue-light pulse creating abnormal cation influx during the repolarization phase of the hiAM AP. Results 4AP induced a 82.4 ± 27.8 ms increase of AP duration at 90% repolarization (APD90) values in hiAM monolayers. Using APs recorded under control conditions (CTL) as reference, the APqr maneuver reduced this APD90 difference to 1.9 ± 3.1 ms. Similarly, APqr suppressed the effects of light-induced abnormal cation influx on APD90 (CTL: 342.9 ± 51.7 ms, blue-light pulse: 700.8 ± 64.5 ms, APqr: 338.3 ± 68 ms) effectively, with Vm deviation less than 2.5 mV in 96.7% of the time. APqr could also be applied for the enforcement of arbitrary AP shapes. In these experiments, the Vm references consisted of AP shapes of hiAM monolayers exposed to drugs with APD-prolonging (4AP) or shortening (carbachol) effects. APqr was able to enforce these reference APs, that were distinctly different from the endogenous AP shapes, on hiAM monolayers with great accuracy, with Vm deviations less than 2.5 mV in 95.8% and 94.4% of the time, respectively. Conclusions APqr restores AP morphologies in the presence of electrical perturbations of different origin without any prior knowledge about the disturbance and enforces arbitrary AP morphologies with high accuracy in an immediate and self-regulatory manner. Collectively, these results set the stage for in-depth investigations into the regulatory roles of Vm in healthy and diseased cardiomyocytes via the application of such real-time opto-electronic control systems.Real-time (re)shaping of cardiac APs

Photoinactivation of Escherichia coli by 405nm and 450nm light-emitting diodes: Comparison of continuous wave and pulsed light.

Antimicrobial blue light (ABL) therapy is one of the novel non-antibiotic approaches and recent studies showed the potential of pulsed ABL. Comparing photoinactivation effect of continuous wave (CW) and pulsed blue light and investigating the impact of varying light parameters. E. coli cells in planktonic were treated with CW and pulsed light (405nm and 450nm) at 60 mW/cm2, and the samples were taken to assess survival, reactive oxygen species (ROS) level, damage of cell membrane and metabolic activity. Further, a ROS scavenger was used to find the role of ROS played in ABL therapy. E. coli was more sensitive to 405nm light and the photoinactivation was dose-dependent. Pulsed 405nm light showed the better antimicrobial effect on E. coli and caused increasing damage of cell membrane. It might be attributed to the ROS production in bacteria. Pulsed light has a potential of improving the efficacy of ABL therapy and is worth to be explored deeply further.

Improved separation of quartz optically stimulated luminescence from a mixed sample using pulsed green light

In the luminescence dating of samples containing both quartz and feldspar (e.g. fine silt, or unseparated rock), the infra-red stimulated luminescence (IRSL) from feldspar is most often used, even though the luminescence characteristics of the OSL from quartz are better understood, and quartz OSL is known to be more stable than feldspar IRSL and more readily reset when exposed to daylight. Unfortunately, in almost all unseparated samples giving both quartz and feldspar luminescence signals, the feldspar OSL (stimulated by blue or green wavelengths) intensity is similar to, or greater than, that from quartz. Separation of quartz and feldspar signals has been achieved before using prior IR and/or pulsed visible light stimulation. This study investigates whether using pulsed green stimulation after IR stimulation gives better discrimination in favour of quartz optically stimulated luminescence (OSL) than using post-IR pulsed blue stimulation, by using the luminescence response of single mineral rocks (quartzite, potassium feldspar) at various temperatures. The results presented here support the view that pulsed blue and pulsed green stimulation of quartz (quartzite or calibration quartz grains) both excite charge to the conduction band, resulting in only a minor dependence on the temperature of the blue or green stimulation. We also confirm that IR depletes the quartz OSL signal only if undertaken at elevated temperature (>125 °C). In contrast, all 3 light sources can result in luminescence from potassium-rich feldspar, but the post-infrared pulsed blue light stimulated luminescence (post-IR PBSL) signal is significantly less dependent on the prior IR stimulation temperature than the post-infrared pulsed green light stimulated luminescence (post-IR PGSL) signal. This is presumably because green stimulation excites mainly into the band-tails. As a consequence, it is shown that the contribution of feldspar OSL to pulsed-green light stimulated luminescence (PGSL) is reduced more by a prior IR stimulation at elevated temperature, than the corresponding pulsed-blue light stimulated luminescence (PBSL). These results are consistent with the band models used to describe the origins of quartz and feldspar luminescence proposed by previous studies. We conclude that the post-IR PGSL provide better discrimination in favour of quartz OSL than does the corresponding post-IR PBSL, and that this should be taken advantage of in future studies on samples with mixed sources of luminescence.

Effects of Pulsed Light on Mycelium Growth and Conidiation in Aspergillus oryzae

Understanding how Aspergillus oryzae responds to light is critical for developing efficient light regulation strategies in the brewing and waste treatment industries. Although continuous light is known to restrict A. oryzae, little is known about A. oryzae’s sensitivity to light with photoperiod. In this study, we used pulse wave modulation (PWM) to generate nine pulsed blue light (PBL) treatments with varying peak light intensities and frequencies. The effect of PBL on A. oryzae was then compared to that of continuous blue light (CBL). Our findings showed that A. oryzae GDMCC 3.31 mycelium developed faster and produced more conidia under PBL with specific peak intensities and frequencies than under CBL treatment when the light dose and average light intensity were held constant. The colony diameter and conidia count under the two PBL treatments (PL-20_40%_1 Hz and PL-400_20%_10 kHz) were 1.13 and 1.22 times greater than under the CBL treatments, respectively. This different response may be mainly attributed to A. oryzae’s adaptation to the light–dark cycles in nature. Furthermore, an interactive effect was found between peak light intensity and frequency. This work includes pulsed wave modulation as a new factor that influences the A. oryzae photoresponse and recommends it in the development of light regulation methods for fermentation.

Evaluating the safety and efficacy of aminolevulinic acid 20% topical solution activated by pulsed dye laser and blue light in the treatment of facial cutaneous squamous cell carcinoma in situ.

Squamous cell carcinoma (SCC) is the second most common cutaneous malignancy, after basal cell carcinoma (BCC). Photodynamic therapy (PDT) involves converting a photosensitizer to reactive oxygen intermediates, which preferentially bind to hyperproliferative tissue. The most commonly used photosensitizers are methyl aminolevulinate and aminolevulinic acid (ALA). Presently, ALA-PDT is approved in the US and Canada for the treatment of actinic keratoses on the face, scalp, and upper extremities. This cohort study evaluated the safety, tolerability, and efficacy of aminolevulinic acid, pulsed dye laser, and photodynamic therapy (ALA-PDL-PDT) for treatment of facial cutaneous squamous cell carcinoma in situ (isSCC). Twenty adult patients with biopsy-confirmed isSCC on the face were recruited. Only lesions 0.4-1.3 cm in diameter were included. Patients underwent two treatments with ALA-PDL-PDT spaced 30 days apart. The isSCC lesion was then excised 4-6 weeks following the second treatment for histopathological assessment. No residual isSCC was detected in 17/20 (85%) patients. Two of the patients with residual isSCC had skip lesions present that explained the treatment failure. Excluding the patients with skip lesions, the posttreatment histological clearance rate was 17/18 (94%). Minimal side effects were reported. Our study was limited by small sample size and lack of long-term recurrence data. The ALA-PDL-PDT protocol is a safe and well-tolerated treatment option for isSCC on the face, providing excellent cosmetic and functional results.

Sequential absorption of two photons creates a bistable form of RubyACR responsible for its strong desensitization

Channelrhodopsins with red-shifted absorption, rare in nature, are highly desired for optogenetics because light of longer wavelengths more deeply penetrates biological tissue. RubyACRs (Anion ChannelRhodopsins), a group of four closely related anion-conducting channelrhodopsins from thraustochytrid protists, are the most red-shifted channelrhodopsins known with absorption maxima up to 610nm. Their photocurrents are large, as is typical of blue- and green-absorbing ACRs, but they rapidly decrease during continuous illumination (desensitization) and extremely slowly recover in the dark. Here, we show that long-lasting desensitization of RubyACRs results from photochemistry not observed in any previously studied channelrhodopsins. Absorption of a second photon by a photocycle intermediate with maximal absorption at 640nm (P640) renders RubyACR bistable (i.e., very slowly interconvertible between two spectrally distinct forms). The photocycle of this bistable form involves long-lived nonconducting states (Llong and Mlong), formation of which is the reason for long-lasting desensitization of RubyACR photocurrents. Both Llong and Mlong are photoactive and convert to the initial unphotolyzed state upon blue or ultraviolet (UV) illumination, respectively. We show that desensitization of RubyACRs can be reduced or even eliminated by using ns laser flashes, trains of short light pulses instead of continuous illumination to avoid formation of Llong and Mlong, or by application of pulses of blue light between pulses of red light to photoconvert Llong to the initial unphotolyzed state.

Optogenetic control of gut movements reveals peristaltic wave-mediated induction of cloacal contractions and reactivation of impaired gut motility.

Gut peristalsis, recognized as a wave-like progression along the anterior-posterior gut axis, plays a pivotal role in the transportation, digestion, and absorption of ingested materials. The embryonic gut, which has not experienced ingested materials, undergoes peristalsis offering a powerful model for studying the intrinsic mechanisms underlying the gut motility. It has previously been shown in chicken embryos that acute contractions of the cloaca (an anus-like structure) located at the posterior end of the hindgut are tightly coupled with the arrival of hindgut-derived waves. To further scrutinize the interactions between hindgut and cloaca, we here developed an optogenetic method that produced artificial waves in the hindgut. A variant form of channelrhodopsin-2 (ChR2(D156C)), permitting extremely large photocurrents, was expressed in the muscle component of the hindgut of chicken embryos using Tol2-mediated gene transfer and in ovo electroporation techniques. The D156C-expressing hindgut responded efficiently to local pulses of blue light: local contractions emerge at an ectopic site in the hindgut, which were followed by peristaltic waves that reached to the endpoint of the hindgut. Markedly, the arrival of the optogenetically induced waves caused concomitant contractions of the cloaca, revealing that the hindgut-cloaca coordination is mediated by signals triggered by peristaltic waves. Moreover, a cloaca undergoing pharmacologically provoked aberrant contractions could respond to pulsed blue light irradiation. Together, the optogenetic technology developed in this study for inducing gut peristalsis paves the way to study the gut movement and also to explore therapeutic methodology for peristaltic disorders.

Optogenetic Activation of PVN-projecting MnPO Neurons Induces Changes in Type I PVN Neurons

The paraventricular nucleus of the hypothalamus (PVN) is an important autonomic control center that receives afferent inputs from the median preoptic nucleus (MnPO). The link between the MnPO and the PVN is essential in generating chronic intermittent hypoxia hypertension. An optogenetic intersectional viral approach was used to gain more insight into the contribution of MnPO inputs to changes in PVN function that could contribute to hypertension. Adult male Sprague-Dawley rats were anesthetized with isoflurane and injected with 100 nL of AAV9.hSyn.HI.eGFP-cre.WPRE.SV40 in the PVN bilaterally and AAV1-Ef1a-DIO-hChR2(H134R)-mCherry-WPRE-HGHpA in the MnPO. This method induced a CRE-dependent expression of channel rhodopsin in PVN-projecting MnPO neurons. Three weeks after the injections, the rats were sacrificed as oblique brain slices of PVN were made. Postsynaptic currents (PSCs) were recorded from PVN neurons (VHold = -70 mV) with an aCSF (2-3 ml/min) bath solution. MnPO axon terminals in the PVN were stimulated with 15 Hz LED-generated blue light (470nM) pulses of 20-ms duration for a total of 1 min with an optical fiber directed at PVN. The stimulation train was repeated 5 times at 5 minutes intervals. PSCs were recorded for 40 minutes, including 5 min baseline periods before stimuli and 10 min post-stimulation period. Cells were characterized as type I, type II, or type III PVN neurons based on the presence of transient outward rectification. Amplitude and frequency data were analyzed offline using Easy Electrophysiology v2.5.0 software from a total of 17 Type I PVN neurons. Optogenetic stimulation evoked EPSC or mixed EPSC/IPSCs in 13 Type I neurons. From the 13 photo-evoked neurons, 10 neurons showed a significant increase in EPSC frequency following stimulation train as compared to the preceding baseline (1st: 6.149±1.438 Hz vs 27.377±5.474 Hz, p=0.0187; 2nd 7.532±1.670 Hz vs 27.562±5.514 Hz, p=0.0161; 3rd 7.395±1.659 Hz vs 25.415±5.028 Hz, p=0.0170; 4th 7.343±1.466 Hz vs 24.225±4.750 Hz, p=0.0183; 5th 6.709±1.375 Hz vs 21.837±4.464 Hz, p=0.0220). In the same neurons, spontaneous EPSC frequency in the first minute after stimulation trains 1 to 4 also was significantly higher than the first pre-stimulus baseline but the effect gradually decreased over time (baseline 6.149±1.438 Hz vs 14.615±3.260 Hz, p=0.0236; vs 12.055±2.519 Hz, p=0.0213; vs 10.904±2.340 Hz, p=0.0247; vs 9.801±2.027 Hz, p=0.0331). There were no changes in EPSC amplitude. Repetitive optogenetic stimulation of MnPO inputs to Type I PVN neurons increased EPSC frequency in a time-dependent manner. Additional experiments will be needed to specify the mechanism behind the increase in frequency and whether this phenomenon occurs in other PVN cell types. P01 HL088052; R01 HL155977 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Height Determination of a Blue Discharge Observed by ASIM/MMIA on the International Space Station

AbstractWe analyze simultaneous photometric observations of thundercloud discharges from the Modular Multispectral Imaging Array of the Atmosphere‐Space Interactions Monitor (ASIM) on board the International Space Station with ground‐based vertical electric field measurements in South Africa on 3 February 2019 at 23:00–23:05 UTC. During this time, ASIM flew over an extended thunderstorm front of several hundreds of kilometers and recorded a blue discharge with the photometer at 337 nm which emitted strong electric fields. It is found that the rising edge of the blue photomultiplier tube light pulse allows the estimation of the blue discharge height: ∼10.9–16.5 km which is constrained by cloud top height in a range of ∼13.3–16.7 km deduced from infrared radiometry on board the geostationary Meteosat satellite. The electric field measurements are used to infer the height of the blue discharge to be ∼16.0–18.8 km by use of skywave arrival times. It is shown that the height determinations are consistent with each other within the measurement uncertainties and the possible presence of an overshooting cloud top is discussed. The height of blue discharges is important to better understand how they can affect the chemistry in the upper troposphere.

Optogenetic termination of atrial tachyarrhythmias by brief pulsed light stimulation

AimsThe most efficient way to acutely restore sinus rhythm from atrial fibrillation (AF) is electrical cardioversion, which is painful without adequate sedation. Recent studies in various experimental models have indicated that optogenetic termination of AF using light-gated ion channels may provide a myocardium-specific and potentially painless alternative future therapy. However, its underlying mechanism(s) remain(s) incompletely understood. As brief pulsed light stimulation, even without global illumination, can achieve optogenetic AF termination, besides direct conduction block also modulation of action potential (AP) properties may be involved in the termination mechanism. We studied the relationship between optogenetic AP duration (APD) and effective refractory period (ERP) prolongation by brief pulsed light stimulation and termination of atrial tachyarrhythmia (AT). Methods and resultsHearts from transgenic mice expressing the H134R variant of channelrhodopsin-2 in atrial myocytes were explanted and perfused retrogradely. AT induced by electrical stimulation was terminated by brief pulsed blue light stimulation (470 nm, 10 ms, 16 mW/mm2) with 68% efficacy. The termination rate was dependent on pulse duration and light intensity. Optogenetically imposed APD and ERP changes were systematically examined and optically monitored. Brief pulsed light stimulation (10 ms, 6 mW/mm2) consistently prolonged APD and ERP when light was applied at different phases of the cardiac action potential. Optical tracing showed light-induced APD prolongation during the termination of AT. ConclusionOur results directly demonstrate that cationic channelrhodopsin activation by brief pulsed light stimulation prolongs the atrial refractory period suggesting that this is one of the key mechanisms of optogenetic termination of AT.

The efficacy and safety of aminolevulinic acid 20% topical solution activated by pulsed dye laser and blue light for the treatment of facial cutaneous squamous cell carcinoma in situ

The efficacy and safety of aminolevulinic acid 20% topical solution activated by pulsed dye laser and blue light for the treatment of facial cutaneous squamous cell carcinoma in situ

Bacterial biofilm reduction by 275 and 455 nm light pulses emitted from light emitting diodes

AbstractEradication of biofilms from the food contact surfaces is a challenging task, owing to their increased resistance to sanitizers and regular cleaning practices. The treatment with the light pulses emitted from the light emitting diode (LED) is an emerging surface decontamination technology, that can produce the antibiofilm effect by photodynamic inactivation. The objective of this study was to understand the antibiofilm efficacy of the 275 (Ultraviolet‐C [UV‐C]) and 455 nm (Blue) light pulses emitted from the LEDs against single and dual‐species biofilms of Salmonella Typhimurium ATCC13311 and Aeromonas australiensis 03‐09 on stainless steel (SS) coupons formed at different time. The biofilm formation by S. Typhimurium was improved when grown with A. australiensis in dual‐species culture. Both 275 and 455 nm light pulses showed significant antibiofilm activity against S. Typhimurium and A. australiensis in single and dual‐species biofilms. For instance, the 275 nm LED treatment of surfaces of SS coupons with 1.8 J/cm2 dose on each surface, produced reductions of 4.24 and 3.9 log (CFU/cm2) in single (cell attachment) and dual‐species biofilms of S. Typhimurium, and reductions of 4.45 and 4.99 log (CFU/cm2) in single and dual‐species biofilms of A. australiensis. However, the susceptibility of A. australiensis toward 455 nm LED treatments was influenced by the presence of S. Typhimurium in the dual‐species biofilm. The confocal laser scanning microscopy images revealed significant cell membrane damage in the dual‐species biofilms by the LED treatments with 275 and 455 nm light pulses. Overall, several factors like surface temperature increase, strains used, treatment dose, treatment time, and incubation period of biofilms influenced the inactivation efficacy of the 275 and 455 nm LED treatments against the biofilms formed on SS coupons. This study provides an insight into the inactivation efficacy of LED light pulses against bacterial biofilms on food grade SS surfaces.

Optogenetic Stimulation Array for Confocal Microscopy Fast Transient Monitoring.

Optogenetics is an emerging discipline with multiple applications in neuroscience, allowing to study neuronal pathways or serving for therapeutic applications such as in the treatment of anxiety disorder, autism spectrum disorders (ASDs), or Parkinson's disease. More recently optogenetics is opening its way also to stem cell-based therapeutic applications for neuronal regeneration after stroke or spinal cord injury. The results of optogenetic stimulation are usually evaluated by immunofluorescence or flow cytometry, and the observation of transient responses after stimulation, as in cardiac electrophysiology studies, by optical microscopy. However, certain phenomena, such as the ultra-fast calcium waves acquisition upon simultaneous optogenetics, are beyond the scope of current instrumentation, since they require higher image resolution in real-time, employing for instance time-lapse confocal microscopy. Therefore, in this work, an optogenetic stimulation matrix controllable from a graphical user interface has been developed for its use with a standard 24-well plate for an inverted confocal microscope use and validated by using a photoactivable adenyl cyclase (bPAC) overexpressed in rat fetal cortical neurons and the consequent calcium waves propagation upon 100 ms pulsed blue light stimulation.

Progress of phototherapy for osteosarcoma and application prospect of blue light photobiomodulation therapy.

Osteosarcoma (OS) is the most common primary malignant bone tumor that mainly affects the pediatric and adolescent population; limb salvage treatment has become one of the most concerned and expected outcomes of OS patients recently. Phototherapy (PT), as a novel, non-invasive, and efficient antitumor therapeutic approach including photodynamic therapy (PDT), photothermal therapy (PTT), and photobiomodulation therapy (PBMT), has been widely applied in superficial skin tumor research and clinical treatment. OS is the typical deep tumor, and its phototherapy research faces great limitations and challenges. Surprisingly, pulse mode LED light can effectively improve tissue penetration and reduce skin damage caused by high light intensity and has great application potential in deep tumor research. In this review, we discussed the research progress and related molecular mechanisms of phototherapy in the treatment of OS, mainly summarized the status quo of blue light PBMT in the scientific research and clinical applications of tumor treatment, and outlooked the application prospect of pulsed blue LED light in the treatment of OS, so as to further improve clinical survival rate and prognosis of OS treatment and explore corresponding cellular mechanisms.