Mild Stimuli Research Articles

Renal and segmental artery hemodynamic response to acute, mild hypercapnia

Profound increases (>15 mmHg) in arterial carbon dioxide (i.e., hypercapnia) reduce renal blood flow. However, a relatively brief and mild hypercapnia can occur in patients with sleep apnea or in those receiving supplemental oxygen therapy during an acute exacerbation of chronic obstructive pulmonary disease. We tested the hypothesis that a brief, mild hypercapnic exposure increases vascular resistance in the renal and segmental arteries. Blood velocity in 14 healthy adults (26 ± 4 yr; 7 women, 7 men) was measured in the renal and segmental arteries with Doppler ultrasound while subjects breathed room air (Air) and while they breathed a 3% CO2, 21% O2, 76% N2 gas mixture for 5 min (CO2). The end-tidal partial pressure of CO2 ([Formula: see text]) was measured via capnography. Mean arterial pressure (MAP) was measured beat to beat via the Penaz method. Vascular resistance in the renal and segmental arteries was calculated as MAP divided by blood velocity. [Formula: see text] increased with CO2 (Air: 45 ± 3, CO2: 48 ± 3 mmHg, P < 0.01), but there were no changes in MAP (P = 0.77). CO2 decreased blood velocity in the renal (Air: 35.2 ± 8.1, CO2: 32.2 ± 7.3 cm/s, P < 0.01) and segmental (Air: 24.2 ± 5.1, CO2: 21.8 ± 4.2 cm/s, P < 0.01) arteries and increased vascular resistance in the renal (Air: 2.7 ± 0.9, CO2: 3.0 ± 0.9 mmHg·cm-1·s, P < 0.01) and segmental (Air: 3.9 ± 1.0, CO2: 4.4 ± 1.0 mmHg·cm-1·s, P < 0.01) arteries. These data provide evidence that the kidneys are hemodynamically responsive to a mild and acute hypercapnic stimulus in healthy humans.

Optimization of food deprivation and sucrose preference test in SD rat model undergoing chronic unpredictable mild stress.

BackgroundThe chronic unpredictable mild stress (CUMS) model has long been considered the best model for exploring the pathophysiological mechanisms underlying depression. However, there are no widely recognised standards for strategies for modeling and for behavioral testing. The present study aimed to optimize the protocols for food deprivation and the sucrose preference test (SPT) for the CUMS model.MethodsWe first evaluated the effects of different long periods of food deprivation on the body weight of Sprague Dawley (SD) rats by testing food deprivation for 24 hours (8:00‐8:00+), food deprivation for 12 hours during the daytime (8:00‐20:00) and food deprivation for 12 hours at night (20:00‐8:00+). Next, we established a SD rat CUMS model with 15 different stimulations, and used body weight measurement, SPT, forced swim test (FST), open field test (OFT) and Morris water maze (MWM) test to verify the success of the modeling. In the SPT, consumption of sucrose and pure water within 1 and 12 hours was measured.ResultsTwelve hours of food deprivation during the daytime (8:00‐20:00) had no effect on body weight, while 12 hours of food deprivation at night (20:00‐8:00+) and 24 hours of food deprivation (8:00‐8:00+) significantly reduced the mean body weight of the SD rats. When SPT was used to verify the successful establishment of the CUMS rat model, sucrose consumption measured within 12 hours was less variable than that measured within 1 hour.ConclusionsTwelve hours of food deprivation in the daytime (8:00‐20:00) may be considered a mild stimulus for the establishment of a CUMS rat model. Measuring sucrose consumption over 12 hours is recommended for SPT.

Deficiency of Prebiotic Fiber and Insufficient Signaling Through Gut Metabolite-Sensing Receptors Leads to Cardiovascular Disease.

High blood pressure (BP) continues to be a major, poorly controlled but modifiable risk factor for cardiovascular death. Among key Western lifestyle factors, a diet poor in fiber is associated with prevalence of high BP. The impact of lack of prebiotic fiber and the associated mechanisms that lead to higher BP are unknown. Here we show that lack of prebiotic dietary fiber leads to the development of a hypertensinogenic gut microbiota, hypertension and its complications, and demonstrate a role for G-protein coupled-receptors (GPCRs) that sense gut metabolites. One hundred seventy-nine mice including C57BL/6J, gnotobiotic C57BL/6J, and knockout strains for GPR41, GPR43, GPR109A, and GPR43/109A were included. C57BL/6J mice were implanted with minipumps containing saline or a slow-pressor dose of angiotensin II (0.25 mg·kg-1·d-1). Mice were fed diets lacking prebiotic fiber with or without addition of gut metabolites called short-chain fatty acids ([SCFA)] produced during fermentation of prebiotic fiber in the large intestine), or high prebiotic fiber diets. Cardiac histology and function, BP, sodium and potassium excretion, gut microbiome, flow cytometry, catecholamines and methylation-wide changes were determined. Lack of prebiotic fiber predisposed mice to hypertension in the presence of a mild hypertensive stimulus, with resultant pathological cardiac remodeling. Transfer of a hypertensinogenic microbiota to gnotobiotic mice recapitulated the prebiotic-deprived hypertensive phenotype, including cardiac manifestations. Reintroduction of SCFAs to fiber-depleted mice had protective effects on the development of hypertension, cardiac hypertrophy, and fibrosis. The cardioprotective effect of SCFAs were mediated via the cognate SCFA receptors GPR43/GPR109A, and modulated L-3,4-dihydroxyphenylalanine levels and the abundance of T regulatory cells regulated by DNA methylation. The detrimental effects of low fiber Westernized diets may underlie hypertension, through deficient SCFA production and GPR43/109A signaling. Maintaining a healthy, SCFA-producing microbiota is important for cardiovascular health.

All-Optical Electrophysiology Reveals the Role of Lateral Inhibition in Sensory Processing in Cortical Layer 1

Cortical layer 1 (L1) interneurons have been proposed as a hub for attentional modulation of underlying cortex, but the transformations that this circuit implements are not known. We combined genetically targeted voltage imaging with optogenetic activation and silencing to study the mechanisms underlying sensory processing in mouse barrel cortex L1. Whisker stimuli evoked precisely timed single spikes in L1 interneurons, followed by strong lateral inhibition. A mild aversive stimulus activated cholinergic inputs and evoked a bimodal distribution of spiking responses in L1. A simple conductance-based model that only contained lateral inhibition within L1 recapitulated the sensory responses and the winner-takes-all cholinergic responses, and the model correctly predicted that the network would function as a spatial and temporal high-pass filter for excitatory inputs. Our results demonstrate that all-optical electrophysiology can reveal basic principles of neural circuit function invivo and suggest an intuitive picture for how L1 transforms sensory and modulatory inputs. VIDEO ABSTRACT.

Delayed recovery from general anaesthesia associated with pre-existing neurological disease in a horse

A seven-year-old gelding presented for surgical management of right-sided olecranon bursitis. Preanaesthetic examination revealed a right-sided head tilt which had been present since birth. General anaesthesia and surgery went smoothly...

Choose change: Situation modification, distraction, and reappraisal in mild versus intense negative situations

Despite the theoretical importance and applied potential of situation modification as an emotion regulation strategy, empirical research on how people change situations to regulate their emotions is scarce. Meanwhile, existing paradigms typically allowed participants to avoid the entire situation, thus confounding situation modification with situation selection. In our current experiments, participants could choose between partially modifying their negative emotional environment without avoiding it entirely and two well-established emotion regulation strategies (reappraisal and distraction). Participants did choose situation modification (Experiments 1–2) and they did so more often for intense than for mild stimuli in Experiment 2. In addition, modifying the stimulus display effectively helped downregulating negative affect (Experiments 1–2). Finally, in both experiments, participants opted more for distraction for intense compared to mild stimuli, while they opted more for reappraisal for mild compared to intense stimuli. Presenting a first step in developing a paradigm that allows people to exert control over but to not avoid emotion-provoking situations, we thus show that changing one’s environment helps regulating one’s emotions. More generally, our findings indicate that people prefer to regulate their emotions using disengagement strategies (situation modification and distraction) with high-intensity relative to low-intensity negative situations, while they prefer engagement strategies (reappraisal) with low-intensity relative to high-intensity negative situations.

Enzymatically mediated, physiologically triggered N-palmitoyl chitosan hydrogels with temporally modulated high injectability

Injectable hydrogels ideally are low-viscosity liquids when being pushed through a syringe needle and quickly form gels after injection. Physiologically triggered injectable hydrogels based on stimuli-responsive polymers induce sol to gel transitions via pH or temperature alteration, however, such mild environmental stimuli are often prone to be inefficient for triggering the rapid and drastic transition from low-viscosity liquids to form-stable hydrogels. Here, an enzyme mediation strategy to regulate, transmit, and amplify the environmental stimuli is presented for efficient formation of hydrogels with high injectability and stability. The urease-regulated biocatalytic reaction initially inhibited at slightly acidic pH and room temperature is integrated with a pH-responsive system of aqueous N-palmitoyl chitosan (NPCS), acquiring temporally modulated high injectability. After injection to physiological environments, the enzyme activity is significantly enhanced with the elevated pH and temperature, resulting in fast enzymatic generation of a base, which in turn triggers the efficient hydrogelation of aqueous NPCS.

Trigeminal Neuralgia: Microvascular Decompression is the Ultimate Answer

Trigeminal neuralgia also known as ‘Fothergill’s disease’ or ‘tic douloureux’ is a very peculiar disease. The severe pain is paroxystic and can be triggered by a mild cutaneous stimulus on the face or “trigger zone”. The disease has a wide variety of etiology and clinical presentation. The management will include both medical and a surgical approach. A 58-year-old female patient had reported with a complaint of pain for 8 years. On thorough history taking and clinical examination, we were able to confirm the final diagnosis as trigeminal neuralgia (TN). We present a case of trigeminal neuralgia of the maxillary and mandibular division along with clinical history, MRI (Magnetic Resonance Imaging) findings and treatment approach.&#x0D; Bang. J Neurosurgery 2019; 8(2): 105-107

Reversible Aggregation of Chlorophyll Derivative Induced by Phase Transition of Lipid.

Controlling the supramolecular organization of pigment molecules will provide innovative materials that exhibit variable optical properties. In nature, photosynthetic systems employ chlorophyllous supramolecules in which each pigment molecule is suitably organized in proteins, and their properties are adequately optimized by changing the structures of the surrounding amino acid residues. Here, we report a strategy for varying the aggregation behavior of a chlorophyll derivative by using a phase-transition phenomenon of lipid bilayers. Methyl pyropheophorbide a (MPP) was employed as a chlorophyllous pigment in our artificial system, and synthetic phosphatidylcholines with saturated acyl chain(s) were also used. The MPP molecules successfully accumulated within the lipid bilayer of liposomes without changing the vesicular structure. When the lipid bilayer was in a gel form (under the phase-transition temperature, Tm), the embedded MPP aggregated to yield a dimeric form showing red-shifted absorption bands and circular dichroism signals. When the solutions of MPP-containing liposomes were heated to higher temperatures than their Tm, MPP disaggregated to monomeric form as the absorption spectrum changed into its original fashion in dichloromethane. The reversible thermochromic (dis)aggregation of the MPP molecules had good cyclability. Additional careful examination of the phase transition in the MPP-lipid co-assemblies clarified that the critical temperatures of the MPP (dis)aggregation were in good agreement with the phase-transition temperatures of the pigment-containing bilayers. The reversible MPP aggregation in the lipid bilayers occurred in a wide range of temperatures (around 10-55 °C) by changing the length of the diacyl side chains of phospholipids. The reversible thermochromism of the chlorophyllous system was established by varying the nature of the surrounding lipid bilayer. This study can provide a useful strategy for making variable tetrapyrrolic aggregate systems induced by mild extrinsic stimuli.

Resolution of Hypothyroidism Restores Cold-Induced Thermogenesis in Humans.

Background: Hypothyroidism is a frequent endocrine disorder with common symptoms of increased cold sensitivity and unintended weight gain, indicating changes in energy expenditure (EE) and response to cold exposure. Thyroid hormones (TH) play an important role for proper function of brown adipose tissue (BAT) and cold-induced thermogenesis (CIT) in rodents, but the role of hypothyroidism on CIT in humans is uncertain.Methods: This was a prospective observational study. Forty-two patients presenting with subclinical or overt hypothyroidism in whom TH replacement was planned were recruited. Thirty-three patients completed the study. Thermogenesis was measured by indirect calorimetry during warm conditions and after a mild cold stimulus of 90 minutes, both during the hypothyroid state and after at least three months of sufficient TH replacement. CIT was determined as the difference between EE during mildly cold and warm conditions. The primary endpoint was the change of CIT between the hypothyroid and euthyroid state.Results: EE during warm conditions increased from a median of 1330 (interquartile range [IQR] 1251–1433) kcal/24 hours in the hypothyroid state to a median of 1442 (IQR 1294–1579) kcal/24 hours in the euthyroid state (+8.5%; p = 0.0002). EE during mild cold exposure increased from 1399 (IQR 1346–1571) kcal/24 hours to 1610 (IQR 1455–1674) kcal/24 hours (+15%; p < 0.0001). The median CIT was 55 (IQR 1–128) kcal/24 hours at the baseline visit, after restoration of euthyroidism CIT increased by 102% to a median of 111 (IQR 15.5–200) kcal/24 hours (p = 0.011). Serum levels of free thyroxine at the respective visit and mean outdoor temperature during the preceeding 30 days were significantly associated with CIT (p = 0.021 and p = 0.001, respectively).Conclusion: Restoring euthyroidism significantly increases CIT in hypothyroid humans.

The neuroscience of trust

Decision-Making Negative emotional states have a powerful effect on decision-making. In an effort to map the interaction of the two within the human brain, Engelmann et al. set up 41 participants in an investment simulation. The participants had to decide how much money they would give to anonymous human “trustees” versus “banks”—computers programmed for the task. These two scenarios were further subdivided by pain: Subjects faced strong electric shocks in some blocks and mild electric stimuli in others. The participants gave less money, in general, when faced with the threat of shock. Furthermore, activity in areas of the brain associated with trust and empathy was suppressed in trustee-dependent decisions during threat of shock. Sci. Adv. 10.1126/sciadv.aau3413 (2019).

Unraveling the mechanochemical synthesis and luminescence in MnII-based two-dimensional hybrid perovskite (C4H9NH3)2PbCl4

The mechanochemical route is a facile and fast way and has received much attention for developing versatile advanced functional materials. Herein, we reported a mechanochemical synthesis for incorporating divalent manganese ions (MnII) into a two-dimensional (2D) hybrid perovskite (C4H9NH3)2PbCl4. The mild external stimuli originating from the grinding at room temperature enabled the formation of MnII-doped 2D hybrid perovskites, and rapidly changed the luminescence characteristics. The photoluminescence analyses show that the violet and orange emissions are attributed to (C4H9NH3)2Pb1– x Mn x Cl4 band-edge emission and the T1→6A1 transition of Mn2+ resulting from an efficient energy transfer process, respectively. Site preference and distribution of the doped Mn2+ cations on the locations of Pb2+ were analyzed. The formation energy calculated by the density functional theory (DFT) indicates that the Mn2+ ions can rapidly enter the crystal lattice due to the unique 2D crystal structure of the hybrid perovskite. Such a case of mechanochemical synthesis for the 2D hybrid perovskite motivates many novel emerging materials and the related applications.

Cochlear Mechanisms and Otoacoustic Emission Test Performance.

This study aims to determine the impact of controlling cochlear-source mechanism on the accuracy with which auditory status is identified using otoacoustic emissions (OAEs) in two groups of subjects with normal hearing (NH) and subjects with mild to moderate hearing loss. Data were collected from 212 subjects with NH and with mild to moderate hearing loss who fell into two categories based on a distortion product OAE (DPOAE) screening protocol: the uncertain-identification group (where errors were likely) and the certain-identification group (where errors were unlikely). DPOAE fine-structure patterns were recorded at intervals surrounding f2 = 1, 2 and 4 kHz (f2/f1 ratio = 1.22), with L2 = 35, 45, and 55 dB SPL (L1/L2 ratio = 10 dB). The discrete cosine transform was used to smooth fine structure, limiting the source contribution to the distortion source only. Reflection-source OAEs were also recorded using amplitude-modulated stimulus frequency OAEs (AM-SFOAE). Area under the relative operating characteristic (AROC) curve was used to quantify test accuracy when the source contribution was controlled versus the condition where both sources contribute. Additionally, failure rate, fixed at 5% for NH ears, as a function of behavioral-threshold category was evaluated. When data for the entire subject group were examined, reducing the reflection-source contribution to the DPOAE did not result in better test performance than the best control condition at any frequency tested. When the subjects with NH were restricted to those with confirmed fine structure, AROC analyses indicated that reducing the reflection-source contribution resulted in several small increases in the accuracy (2%-5%) with which auditory status was identified relative to the best control condition. This improvement was observed for the lowest stimulus levels (i.e., L2 = 35 or 45 dB SPL). In this subset of subjects, distortion-source DPOAEs resulted in more accurate identification of mild hearing loss for a fixed false-positive rate of 5% in NH ears at lower L2's, conditions with poor accuracy in the larger group of subjects. The impact of controlling the source contribution on the identification of moderate losses was less clear in the reduced subject group, with some conditions where the distortion-source DPOAE was more accurate than the control condition and other conditions where there was no change. There was no evidence that reflection-source AM-SFOAEs more accurately identified ears with hearing loss when compared to any of the DPOAE conditions in either the large or reduced group of subjects. While improvements in test accuracy were observed for some subjects and some conditions (e.g., mild hearing losses and low stimulus levels in the reduced subset of subjects), these results suggest that restricting cochlear source contribution by "smoothing" DPOAE fine structure is not expected to improve DPOAE test accuracy in a general population of subjects. Likewise, recording reflection-source OAEs using the AM-SFOAE technique would not be expected to more accurately identify hearing status compared to mixed- or single-source DPOAEs.

Immobilization of American Beaver (Castor canadensis) with Nalbuphine, Medetomidine, and Azaperone

Thirty-two American beavers (Castor canadensis) were immobilized with a mixture of nalbuphine, medetomidine, and azaperone (NalMedA) for tail transmitter placement and health assessments prior to translocation. Inductions and reversals were very smooth, but regardless of the dose administered, which ranged from 0.02 to 0.06 mL/kg, many beavers reacted to mild stimuli such as being lifted out of the cage, drawing blood from the tail, expressing anal glands for sex determination, and turning on isoflurane to deepen anesthesia before placement of tail transmitters. On a scale from 1 to 5, a sedation score of 4 was achieved in 8/32 beavers and a sedation score of 5 in 1/32 of beavers given a mean (SD) dosage of 0.04 (0.01) mL/kg NalMedA, which equated to a mean of 1.09 (0.21) mg/kg nalbuphine, 0.43 (0.09) mg/kg medetomidine, and 0.36 (0.07) mg/kg azaperone. All other animals achieved lower sedation scores. Supplementary isoflurane was needed to deepen anesthesia before tail transmitter placement. Although Nal-MedA appeared to be safe for use in American beavers, the level of sedation achieved was quite variable. Supplementary oxygen is recommended to reduce hypoxemia.

Rational Design of Organic Probes for Turn-On Two-Photon Excited Fluorescence Imaging and Photodynamic Therapy

Summary The rational design of two-photon absorption (2PA) organic dyes with 2PA cross-section (δ) values tunable by mild stimuli under physiological conditions remains a challenge. Using a simulation-assisted structure screening method, we have designed an acetal terminated distyrylbenzene derivative (Ace-DSB), which can be readily converted into aldehyde terminated molecules (Ald-DSB) to exhibit a significant increase in δ values at 760 nm. The conversion reaction, which dramatically turns on the 2PA absorption capability of the molecules, can occur in an intracellular environment. Furthermore, Ald-DSB exhibits 40 times higher efficiency of two-photon generation of singlet oxygen than Ace-DSB. These turn-on features allow enhanced two-photon laser confocal scanning microscopic imaging and two-photon excited photodynamic therapy (2PE-PDT) for MCF-7 cancer cells and melanoma tumors. This work opens a new avenue toward the design of turn-on-type two-photon absorption molecules for both in vitro and in vivo tumor imaging and 2PA-PDT.

Anilinium Salts in Polymer Networks for Materials with Mechanical Stability and Mild Thermally Induced Dynamic Properties.

Dynamic nucleophilic exchange of quaternary anilinium salts has been incorporated into rehealable and malleable polymeric materials that can be activated under mild (60 °C) thermal stimulus. The mechanism of dynamic exchange between quaternary anilinium salt and free aniline was assessed in small-molecule model experiments. The dynamic exchange was found to be dissociative in nature, due to the indirect SN2 mechanism, where initially the bromide anion attacks the anilinium salt to generate an alkyl bromide which undergoes subsequent attack by a free aniline group. A quaternary anilinium-based cross-linker was synthesized to act as dynamic linkages in the polymer network. Cross-linked polymeric materials showed thermoresponsive rehealing and malleability properties at 60 °C along with being resistant to irreversible creep under ambient conditions. The use of anilinium salts enables dynamic exchange to occur with significantly milder thermal stimulus than other comparable materials, while maintaining mechanical stability.

Lipids alter microbial transport through intestinal mucus.

Mucus constitutes a protective layer which coats the gastrointestinal tract, controlling interactions of both commensal and pathogenic microbes with underlying tissues. Changes to the mucus barrier, for example due to altered mucin expression or external stimuli, may impact interactions with microbes and thus potentially contribute to altered gut homeostasis, onset of inflammation, or pathogen invasion. Food-associated stimuli, including lipids, have been shown to change mucus barrier properties and reduce transport of model drug carriers through mucus. Here, we explore the impact of lipids, specifically triglycerides in a model intestinal medium mimicking a fed state, on Escherichia coli (E. coli) transport through mucus by directly imaging swimming patterns and analyzing associated changes in mucus structure. Lipids in model fed state intestinal contents reduced E. coli speed and track linearity within mucus. These changes may be due in part to changes in molecular interactions within the mucus network as well as crowding of the mucus network by lipid emulsion droplets, which visibly stay intact in the mucus gel. In addition, observed physical interactions between bacteria and lipid structures may impact microbial speed and trajectories. As lipids are normal food components and thus represent safe, mild stimuli, these results support exploration of lipid-based strategies to alter the mucus barrier to control interactions with microbes and potentially prevent microbial invasion of underlying epithelium.

Increased inhibition following negative cues: A possible role for enhanced processing

Based on findings showing that attention is captured by aversive stimuli, previous studies have hypothesized that inhibition of return (IOR) is reduced at spatial locations previously occupied by threat cues. Yet evidence for this view is limited: Only a few studies have demonstrated a reduced degree of IOR following threat cues, while most have not found differences in IOR between aversive and neutral cues. In contrast to previous studies that used the spatial cuing paradigm and for the most part employed mild negative stimuli as cues, we examined the influence of highly aversive, colored and complex pictures of real life situations. As opposed to the stimuli used in previous studies, these pictures are thought to result in enhanced processing as well as in specific enhancement for threat pictures in comparison to neutral ones. Based on evidence indicating that enhanced processing of spatial cues results in increased IOR, we hypothesized that the negative picture cues employed in the present study would yield increased IOR. This hypothesis was confirmed in two experiments. We suggest that the enhancement of IOR following highly threatening cues may be related to efficient spatial orienting of attention in response to stimuli that are important from an evolutionary point of view. The results are discussed in the context of neurocognitive mechanisms that may underlie the modulation of IOR by emotional information.

Molecularly‐Engineered, 4D‐Printed Liquid Crystal Elastomer Actuators

AbstractThree‐dimensional structures that undergo reversible shape changes in response to mild stimuli enable a wide range of smart devices, such as soft robots or implantable medical devices. Herein, a dual thiol‐ene reaction scheme is used to synthesize a class of liquid crystal (LC) elastomers that can be 3D printed into complex shapes and subsequently undergo controlled shape change. Through controlling the phase transition temperature of polymerizable LC inks, morphing 3D structures with tunable actuation temperature (28 ± 2 to 105 ± 1 °C) are fabricated. Finally, multiple LC inks are 3D printed into single structures to allow for the production of untethered, thermo‐responsive structures that sequentially and reversibly undergo multiple shape changes.

Enhancement of the stimuli-responsiveness and photo-stability of dynamic diselenide bonds and diselenide-containing polymers by neighboring aromatic groups

The investigation of dynamic covalent bonds, which are exchangeable upon exposure to mild stimuli, represents an important topic toward the development of various advanced systems. Herein, we report enhanced dynamic properties for diselenide bonds that carry neighboring aromatic rings compared to their aliphatic derivatives. The bond exchange reactions in low-molecular-weight and linear polymer systems exhibit a faster equilibration for the aromatic diselenides relative to their aliphatic derivatives either under exposure to visible light or to heating (60 °C) in the dark. This behavior was rationalized in terms of i) the conjugated structures that contribute to the higher sensitivity toward longer-wavelength light, and ii) the homolytic dissociability via resonance stabilization of the dissociated radicals. Quantitative tensile measurements on cross-linked polyurethane in the bulk state revealed an improved healing capacity for those polymers that contain aromatic diselenide moieties relative to those that contain aliphatic diselenides. Furthermore, bulk cross-linked polymers and small molecules that contain aromatic diselenides exhibit higher photo-stability against UV light, demonstrating the potential of these bonds as stable and easy-to-handle dynamic covalent bonds.