Dilator Responses Research Articles

Negative Emotion (dys)regulation Predicts Distorted Time Perception: Preliminary Experimental Evidence and Implications for Psychopathology

ABSTRACTObjectiveAccurate time perception is crucial to daily life but vulnerable to interference, particularly through negative affect, which dilates individuals' sense of time passing. Regulation strategies like rumination, and disorders like borderline personality disorder (BPD), are linked to time distortion, yet their interrelationships remain untested. We investigated whether rumination and BPD symptoms increase time dilation in negative affective states to understand the clinical implications of time distortion.MethodsIn an online pilot study, we tested whether negative affect (NA) predicts subjective time perception and explored how rumination, BPD symptoms, and their interaction predicted time perception using a between‐subjects online experimental mood induction. Adult participants (Ncombined = 760) were recruited from Prolific Academic and a large, Midwestern U.S. university.ResultsState NA and increased BPD features predicted increased time dilation. The role of trait‐level rumination was nuanced, with individuals low in BPD symptoms and elevated trait rumination exhibiting reduced time dilation in response to NA. Conversely, those with elevated rumination and BPD symptoms reported increased time dilation in the neutral condition.ConclusionFindings offer foundational evidence of NA and rumination's roles in time dilation for individuals across levels of BPD symptom endorsement. Subsequent replication and extension could flesh out these relationships and inform psychotherapeutic treatment targets.

Stress–Dilatancy Behavior of Highly Elastic Rubber-Added Cohesionless Materials

Dilatancy is commonly defined as the ratio of the rates of plastic volumetric strain to plastic deviatoric strain, denoted as Dp. Owing to the high modulus of elasticity, the elastic volumetric and deviatoric strain rates under shear stress in conventional cohesionless materials are negligible. Therefore, using the ratio of the rates of total volumetric to deviatoric strain (Dt) as an approximation is common in studying stress–dilatancy behavior and calibrating dilatancy model parameters. This approach is also common in the study of rubber-added cohesionless materials (RCM). However, RCM with a common range of rubber content exhibit a significantly lower modulus of elasticity compared to conventional cohesionless materials. Further research is needed to evaluate the potential impact of elastic strain rates in RCM on stress–dilatancy analysis. Therefore, comparisons were conducted on the stress–dilatancy responses of a series of tests on RCM, where dilatancy is calculated by Dp and Dt, respectively. Furthermore, a modified method for calibrating the parameters of a state-dependent dilatancy model considering Dp is presented. It turns out that Dp is better suited and more precise for dilatancy analysis on highly elastic RCM. Additionally, the dilatancy model can more precisely capture the test results of RCM with parameters calibrated by the proposed method.

Hearing Impairment: Reduced Pupil Dilation Response and Frontal Activation During Degraded Speech Perception.

A relevant aspect of listening is the effort required during speech processing, which can be assessed by pupillometry. Here, we assessed the pupil dilation response of normal-hearing (NH) and hard of hearing (HH) individuals during listening to clear sentences and masked or degraded sentences. We combined this assessment with functional magnetic resonance imaging (fMRI) to investigate the neural correlates of the pupil dilation response. Seventeen NH participants (Mage = 46 years) were compared to 17 HH participants (Mage = 45 years) who were individually matched in age and educational level. Participants repeated sentences that were presented clearly, that were distorted, or that were masked. The sentence intelligibility level of masked and distorted sentences was 50% correct. Silent baseline trials were presented as well. Performance measures, pupil dilation responses, and fMRI data were acquired. HH individuals had overall poorer speech reception than the NH participants, but not for noise-vocoded speech. In addition, an interaction effect was observed with smaller pupil dilation responses in HH than in NH listeners for the degraded speech conditions. Hearing impairment was associated with higher activation across conditions in the left superior temporal gyrus, as compared to the silent baseline. However, the region of interest analysis indicated lower activation during degraded speech relative to clear speech in bilateral frontal regions and the insular cortex, for HH compared to NH listeners. Hearing impairment was also associated with a weaker relation between the pupil response and activation in the right inferior frontal gyrus. Overall, degraded speech evoked higher frontal activation than clear speech. Brain areas associated with attentional and cognitive-control processes may be increasingly recruited when speech is degraded and are related to the pupil dilation response, but this relationship is weaker in HH listeners. https://doi.org/10.23641/asha.27162135.

Increasing plant protein in the diet induces changes in the plasma metabolome that may be beneficial for metabolic health. A randomized crossover study in males

Background & aimDietary shifts replacing animal protein (AP) with plant protein (PP) sources have been associated with lowering cardiometabolic risk (CMR), but underlying mechanisms are poorly characterized. This nutritional intervention aims to characterize the metabolic changes induced by diets containing different proportions of AP and PP sources in males at CMR. DesignThis study is a 4-week, crossover, randomized, controlled-feeding trial in which 19 males with CMR followed two diets providing either 36% for the control diet (CON-D) or 64% for the flexitarian diet (FLEX-D) of total protein intake from PP sources. Plasma nontargeted metabolomes (LC-MS method) were measured in the fasted state and after a high-fat challenge meal at the end of each intervention arm. Lipogenesis and protein synthesis fluxes, flow-mediated dilatation (FMD) and gluco-lipidic responses were assessed after the challenge meal. Data were analyzed with mixed models, and univariate and multivariate models for metabolomics data. ResultsIn both arms CMR improved with time, with decreased body weight (-0.9%), insulin resistant (-34%, HOMA-IR, Homeostatic Model Assessment for Insulin Resistance) and low-density lipoproteins (LDL)-cholesterol (-11%). Diet had no effect on FMD or metabolic fluxes, but a trend was observed for a stronger decrease in HOMA-IR and lower postprandial glucose after FLEX-D vs CON-D. The abundance of 21 and 37 metabolites differed between diets at fasted and fed states, respectively, including food intake biomarkers of AP (methylhistidine, eicosapentaenoic acid, hydroxyprolines) and PP sources (trigonelline, N-acetyl-ornithine). In fasted or fed states, indole acrylic acid and indole propionic acid, both products of tryptophan catabolism, were higher after FLEX-D vs CON-D, while the indispensable amino acids-related metabolites alpha-aminoadipic acid, hydroxymethylbutyric acids and propionylcarnitine were lower. In the postprandial state only, the ω-oxidation products dodecanedioic, tetradecanedioic and hexadecanedioic acids were higher after FLEX-D vs CON-D. ConclusionsDespite little changes in risk factors after 4 wk, this study evidenced subtle metabolic adaptations in amino acids and lipid metabolism and gut microbiota activity occurring after higher PP source intake that may be beneficial to CMR. ClinicalTrials.gov study identifierNCT04236518 Clinical Trial RegistryNCT04236518 on ClinicalTrials.gov

Five weeks of intermittent hand exposures to alternating cold and hot stimuli do not modify finger cold-induced vasodilatation response.

We tested the hypothesis that prolonged intermittent hand exposures to transient contrast thermal stimuli would enhance the finger cold-induced vasodilatation (CIVD) response during localized cooling. Eight healthy men participated in a 5-week regimen, during which they immersed, thrice per week, the non-dominant (EXP) hand in 8° and 43°C water, sequentially and at 3-min intervals, for a total period of 60min. The contralateral (i.e., dominant) hand served as the control (CON) hand. Before and after the regimen, subjects conducted two 30-min hand cold (8°C water) provocation trials, one with the EXP hand and the other with the CON hand. In addition, a flow-mediated dilatation test was performed in the brachial artery of the EXP arm. Regardless of the hand tested, the average finger skin temperature [CON hand: pre-trial=10.5 (1.2)°C, post-trial=10.8 (1.3)°C and EXP hand: pre-trial=10.7 (1.1)°C, post-trial 10.9 (1.1)°C; p=0.79], and the incidence of CIVD events [CON hand: pre-trial=1.1 (1.2) events, post-trial=1.2 (1.1) events and EXP hand: pre-trial=1.1 (0.8) events, post-trial=1.1 (0.8) events; p=0.88] were not affected by the 5-week regimen. The sensation of cold-induced pain was transiently alleviated following the regimen (p=0.02). The flow-mediated dilatation response of the EXP brachial artery remained unaltered [pre-trial=5.4 (3.2)%, post-trial=4.7 (3.6)%; p=0.51]. Therefore, five weeks of intermittent hand exposures to alternating cold and hot stimuli do not improve finger temperature responsiveness to sustained localized cold.

The Pupillary Light-Off Reflex in Acute Disorders of Consciousness.

In intensive care patients with disorders of consciousness, the pupillary light reflex is a measure of pupillary parasympathetic function. By contrast, the pupillary light-off reflex leads to pupil dilation in response to an abrupt change from light to darkness ("light-off") and reflects combined parasympathetic and sympathetic pupillary function. To our knowledge, this reflex has not been systematically investigated in patients with disorders of consciousness. We hypothesized that the pupillary light-off reflex correlates with consciousness levels after acute brain injury. From November 2022 to March 2023, we enrolled 100 study participants: 25 clinically unresponsive (coma or unresponsive wakefulness syndrome) and 25 clinically low-responsive (minimally conscious state or better) patients from the intensive care units of a tertiary referral center, and 50 age-matched and sex-matched healthy controls. Exclusion criteria were active or chronic eye disease. We used automated pupillometry to assess the pupillary light-off reflex and the pupillary light reflex of both eyes under scotopic conditions in all study participants. The pupillary light-off reflex was strongly correlated with consciousness levels (r = 0.62, p < 0.001), the increase in pupillary diameters being smallest in unresponsive patients (mean ± standard deviation 20% ± 21%), followed by low-responsive patients (mean ± standard deviation 47% ± 26%) and healthy controls (mean ± standard deviation 67% ± 17%; p < 0.001). Similar yet less pronounced patterns were observed for the pupillary light reflex. Twenty-one of 25 (84%) unresponsive patients had preserved pupillary light reflexes, but only seven (28%) had fully preserved pupillary light-off reflexes (p < 0.0001). Of these 7 patients, five (71%) regained awareness. The pupillary light-off reflex may be more sensitive to consciousness levels than the pupillary light reflex. The clinical implications of this finding seem worthy of further investigation, particularly regarding possible benefits for neuromonitoring and prognostication after brain injury.

Pupillary dilation response to the auditory food words in adolescents with obesity without binge eating disorder

Childhood obesity is a growing global public health problem. Studies suggest that environmental cues contribute to developing and maintaining obesity. We aimed to evaluate pupillary changes to auditory food words vs. nonfood words and to conduct a dynamic temporal analysis of pupil size changes in adolescents with obesity without binge eating disorder by comparing healthy-weight adolescents. In this study, a total of 63 adolescents aged 12–18 years (n = 32, obesity group (OG); n = 31, control group (CG)) were included. In an auditory paradigm, participants were presented with a series of high and low-calorie food and nonfood words. A binocular remote eye-tracking device was used to measure pupil diameter. Generalized additive mixed models (GAMMs) were used for dynamic temporal analysis of pupillometry data. The results of GAMM analysis indicated that CG had larger pupil dilation than the OG while listening to auditory food words. CG had larger pupil dilation in food words than in nonfood words. However, the OG had a similar pupillary response in food and nonfood words. Pupil dilation response to higher-calorie foods was extended over the later stages of the time period (after 2000 ms) in the OG. In summary, our findings indicated that individuals with obesity had lower pupil dilation to auditory food words compared to normal-weight peers. Adolescents with obesity had prolonged pupillary dilation in higher calories of food words. The individual psychological factors affecting the dynamic changes of pupil responses to food cues in adolescents with obesity should be examined in further studies.

Beneficial Effects of Cocoa Flavanols on Microvascular Responses in Young Men May Be Dependent on Ethnicity and Lifestyle.

Cocoa flavan-3-ols affect endothelium-dependent responses in resistance vessels and microcirculation has received little attention. We tested the effects of dark chocolate consumption (396 mg total flavanols/day for 3 days) in two Groups of 10 men (18-25 years; non-smokers) each comprising equal numbers of White European (WE) and South Asian (SA) ethnicity. In Group 1, dark chocolate did not affect reactive hyperaemia in forearm muscle, but augmented muscle dilatation evoked by acute mental stress, and reactive hyperaemia and acetylcholine (ACh)-evoked dilatation in cutaneous microcirculation. Conversely, in Group 2, chocolate did not affect cutaneous reactive hyperaemia or ACh-evoked dilatation, but these responses were blunted in Group 1 relative to Group 2. Further, when Groups 1 and 2 were combined, responses were blunted in SAs relative to WEs, augmented by chocolate in SAs only. In Group 2 individuals whose ACh-evoked dilatation was attenuated by nitric oxide synthase (NOS) inhibition, ACh-evoked dilatation was not altered after chocolate, but the attenuating effect of NOS inhibition was lost. Conversely, in Group 2 individuals whose ACh-evoked dilatation was enhanced by NOS inhibition, ACh-evoked dilatation was also augmented by chocolate. We propose that in resistance and microvessels of young men, cocoa flavan-3-ols preferentially augment endothelium-dependent dilator responses whose responses are depressed by familial and lifestyle factors more prevalent in SAs than Wes. Flavan-3-ols may facilitate the NOS pathway but also influence other endothelium-dependent dilators.

Peripheral venous dilation using flow-mediated dilation response: A randomized crossover study.

Venodilation is crucial in enhancing the success rate of peripheral intravenous cannulation. Flow-mediated dilation (FMD) is a vasodilatory response initiated by temporary ischemia followed by reperfusion. This crossover study aimed to test the hypothesis that FMD induces dilation of the peripheral veins of the forearm. Fifteen healthy volunteers underwent the FMD and control conditions in a randomized order. FMD involved a 5-min occlusion of blood flow in the brachial artery, followed by reperfusion, achieved by inflating and deflating a cuff placed on the upper arm. The control condition involved participants remaining at rest. The primary outcome measure was a change in the cross-sectional area of the cephalic vein post-intervention. The secondary outcomes included changes in venous diameter and perfusion index (PI). FMD significantly increased the cross-sectional area of the cephalic vein compared with the control condition (relative change to baseline: 37.7% (31.4) vs 2.2% (11.7)), with a mean difference of 35.4% (95% confidence interval (CI): 16.4-54.5, p = 0.001). Both longitudinal and transverse diameters were significantly expanded with FMD compared to the control (relative change to baseline: 15.7% (15.4) vs 2.6% (3.6), p = 0.004; 18.9% (15.6) vs -0.0 (10.2), p = 0.003, respectively). Additionally, PI significantly increased with FMD compared with the control (relative change to baseline: 77.8% (56.9) vs 14.6% (36.0)), with a mean difference of 63.2% (95% CI: 31.2-95.2, p = 0.001). FMD application induced dilation of the cephalic vein of the forearm. The findings suggest that FMD is an effective technique for dilating the venous area and potentially improving the success rate of peripheral intravenous cannulation.

Pupil dilation reflects the social and motion content of faces.

Human facial features (eyes, nose, and mouth) allow us to communicate with others. Observing faces triggers physiological responses, including pupil dilation. Still, the relative influence of social and motion content of a visual stimulus on pupillary reactivity has never been elucidated. A total of 30 adults aged 18-33 years old were recorded with an eye tracker. We analysed the event-related pupil dilation in response to stimuli distributed along a gradient of social salience (non-social to social, going from objects to avatars to real faces) and dynamism (static to micro- to macro-motion). Pupil dilation was larger in response to social (faces and avatars) compared to non-social stimuli (objects), with surprisingly a larger response for avatars. Pupil dilation was also larger in response to macro-motion compared to static. After quantifying each stimulus' real quantity of motion, we found that the higher the quantity of motion, the larger the pupil dilated. However, the slope of this relationship was not higher for social stimuli. Overall, pupil dilation was more sensitive to the real quantity of motion than to the social component of motion, highlighting the relevance of ecological stimulations. Physiological response to faces results from specific contributions of both motion and social processing.

Effects of Phasic Activation of Locus Ceruleus on Cortical Neural Activity and Auditory Discrimination Behavior.

Although the locus ceruleus (LC) is recognized as a crucial modulator for attention and perception by releasing norepinephrine into various cortical regions, the impact of LC-noradrenergic (LC-NE) modulation on auditory discrimination behavior remains elusive. In this study, we firstly recorded local field potential and single-unit activity in multiple cortical regions associated with auditory-motor processing, including the auditory cortex, posterior parietal cortex, secondary motor cortex, anterior cingulate cortex, prefrontal cortex, and orbitofrontal cortex (OFC), in response to optogenetic activation (40 Hz and 0.5 s) of the LC-NE neurons in awake mice (male). We found that phasic LC stimulation induced a persistent high gamma oscillation (50-80 Hz) in the OFC. Phasic activation of LC-NE neurons also resulted in a corresponding increase in norepinephrine levels in the OFC, accompanied by a pupillary dilation response. Furthermore, when mice were performing a go/no-go auditory discrimination task, we optogeneticaly activated the neural projections from LC to OFC and revealed a shortened latency in behavioral responses to sound stimuli and an increased false alarm rate. These impulsive behavioral responses may be associated with the gamma neural activity in the OFC. These findings have broadened our understanding of the neural mechanisms involved in the role of LC in auditory-motor processing.

Investigating dilation response in PET FRP-confined reinforced concrete: Experimental study

In compression, concrete undergoes dilation due to the Poisson’s effect. Beyond the elastic limit, rapid crack propagation causes unstable expansion, leading to stiffness degradation, reduced strength, and ductility. External confinement with fiber-reinforced polymer (FRP) composites effectively manages this dilation, maintaining core integrity at high strength and deformation levels. However, internal steel reinforcement, especially when poorly detailed, can hinder FRP's efficacy by inducing stress concentrations from longitudinal bar buckling, resulting in premature FRP failure. This study addresses this challenge by utilizing polyethylene terephthalate (PET) FRP with a large rupture strain (LRS) capacity to delay premature rupture to high strain levels. Experimental results on poorly detailed reinforced concrete (RC) externally confined with PET FRP are presented, with variables including PET FRP layers, longitudinal bar buckling length, and cross-sectional aspect ratio. Detailed discussions on the effects of these variables on lateral to axial strain ratio, dilation rate, and volumetric response of confined concrete are provided. Test results have shown that PET FRP effectively managed the unstable dilation of confined concrete, even with internal steel reinforcement. Following the yielding of lateral ties and the buckling of longitudinal bars, PET FRP efficiently handled local stress concentrations and redistributed internal concrete damage. Despite PET FRP's low elastic modulus causing significant lateral expansion, its LRS capacity maintained the integrity of the entire column under high deformation.

Combined Effects of Moderate Hypoxia and Sleep Restriction on Mental Workload.

Aircraft pilots face a high mental workload (MW) under environmental constraints induced by high altitude and sometimes sleep restriction (SR). Our aim was to assess the combined effects of hypoxia and sleep restriction on cognitive and physiological responses to different MW levels using the Multi-Attribute Test Battery (MATB)-II with an additional auditory Oddball-like task. Seventeen healthy subjects were subjected in random order to three 12-min periods of increased MW level (low, medium, and high): sleep restriction (SR, <3 h of total sleep time (TST)) vs. habitual sleep (HS, >6 h TST), hypoxia (HY, 2 h, FIO2 = 13.6%, ~3500 m vs. normoxia, NO, FIO2 = 21%). Following each MW level, participants completed the NASA-TLX subjective MW scale. Increasing MW decreases performance on the MATB-II Tracking task (p = 0.001, MW difficulty main effect) and increases NASA-TLX (p = 0.001). In the combined HY/SR condition, MATB-II performance was lower, and the NASA-TLX score was higher compared with the NO/HS condition, while no effect of hypoxia alone was observed. In the accuracy of the auditory task, there is a significant interaction between hypoxia and MW difficulty (F(2-176) = 3.14, p = 0.04), with lower values at high MW under hypoxic conditions. Breathing rate, pupil size, and amplitude of pupil dilation response (PDR) to auditory stimuli are associated with increased MW. These parameters are the best predictors of increased MW, independently of physiological constraints. Adding ECG, SpO2, or electrodermal conductance does not improve model performance. In conclusion, hypoxia and sleep restriction have an additive effect on MW. Physiological and electrophysiological responses must be taken into account when designing a MW predictive model and cross-validation.

A comprehensive physics-based model for the brachial Artery's full flow mediated dilation (FMD) response observed during the FMD test

In this study, a physics-based model is developed to describe the entire flow mediated dilation (FMD) response. A parameter quantifying the arterial wall's tendency to recover arises from the model, thereby providing a more elaborate description of the artery's physical state, in concert with other parameters characterizing mechanotransduction and structural aspects of the arterial wall. The arterial diameter's behavior throughout the full response is successfully reproduced by the model. Experimental FMD response data were obtained from healthy volunteers. The model's parameters are then adjusted to yield the closest match to the observed experimental response, hence delivering the parameter values pertaining to each subject. This study establishes a foundation based on which future potential clinical applications can be introduced, where endothelial function and general cardiovascular health are inexpensively and noninvasively quantified.

Epigenetic regulation by hypoxia, N-acetylcysteine and hydrogen sulphide of the fetal vasculature in growth restricted offspring: A study in humans and chicken embryos.

Fetal growth restriction (FGR) is a common outcome in human suboptimal gestation and is related to prenatal origins of cardiovascular dysfunction in offspring. Despite this, therapy of human translational potential has not been identified. Using human umbilical and placental vessels and the chicken embryo model, we combined cellular, molecular, and functional studies to determine whether N-acetylcysteine (NAC) and hydrogen sulphide (H2S) protect cardiovascular function in growth-restricted unborn offspring. In human umbilical and placental arteries from control or FGR pregnancy and in vessels from near-term chicken embryos incubated under normoxic or hypoxic conditions, we determined the expression of the H2S gene CTH (i.e. cystathionine γ-lyase) (via quantitative PCR), the production of H2S (enzymatic activity), the DNA methylation profile (pyrosequencing) and vasodilator reactivity (wire myography) in the presence and absence of NAC treatment. The data show that FGR and hypoxia increased CTH expression in the embryonic/fetal vasculature in both species. NAC treatment increased aortic CTH expression and H2S production and enhanced third-order femoral artery dilator responses to the H2S donor sodium hydrosulphide in chicken embryos. NAC treatment also restored impaired endothelial relaxation in human third-to-fourth order chorionic arteries from FGR pregnancies and in third-order femoral arteries from hypoxic chicken embryos. This NAC-induced protection against endothelial dysfunction in hypoxic chicken embryos was mediated via nitric oxide independent mechanisms. Both developmental hypoxia and NAC promoted vascular changes in CTH DNA and NOS3methylation patterns in chicken embryos. Combined, therefore, the data support that the effects of NAC and H2S offer a powerful mechanism of human translational potential against fetal cardiovascular dysfunction in complicated pregnancy. KEY POINTS: Gestation complicated by chronic fetal hypoxia and fetal growth restriction (FGR) increases a prenatal origin of cardiovascular disease in offspring, increasing interest in antenatal therapy to prevent against a fetal origin of cardiovascular dysfunction. We investigated the effects between N-acetylcysteine (NAC) and hydrogen sulphide (H2S) in the vasculature in FGR human pregnancy and in chronically hypoxic chicken embryos. Combining cellular, molecular, epigenetic and functional studies, we show that the vascular expression and synthesis of H2S is enhanced in hypoxic and FGR unborn offspring in both species and this acts to protect their vasculature. Therefore, the NAC/H2S pathway offers a powerful therapeutic mechanism of human translational potential against fetal cardiovascular dysfunction in complicated pregnancy.

Effect of Microencapsulated Cocoa Polyphenols on Macro- and Microvascular Function after Eccentric Exercise

Background: Evidence has demonstrated that non-habitual exercise, such as eccentric exercise, can increase reactive oxygen species and induce endothelial dysfunction, which plays a central role in the development of cardiovascular disease. Polyphenol-rich foods, such as cocoa, have been widely investigated in vascular function due to their antioxidant effect. Aims: The goal of this study was to evaluate the impact of microencapsulated cocoa (MC) polyphenols in the flow-mediated dilation (FMD) response and forearm muscle oxygenation (StO2) parameters after an eccentric exercise. Methods: Thirteen physically active adults were enrolled in a randomized, double-blind, and crossover study. FMD and StO2 were evaluated before and after 24 h, 48 h, and 72 h of eccentric exercise and MC or placebo supplementation. Results: No significant difference in FMD response and StO2 parameters was observed after MC and placebo (p &gt; 0.05). Conclusions: A single dose of MC did not change FMD and muscle StO2 parameters after eccentric exercise in healthy individuals.

Holmes-Adie syndrome associated with BNT162b2 mRNA COVID-19 vaccine

Adie’s tonic pupil is a neuro-ophthalmologic disorder with dilation and poor light response. When deep tendon reflex loss accompanies the tonic pupil, it is called Adie syndrome or Holmes-Adie syndrome. The pupillary symptoms result from damage to the ciliary ganglion and the post-ganglionic parasympathetic nerves. Corona virus 2, which causes severe acute respiratory syndrome, has been named corona virus 19 (COVID-19) by the World Health Organization. It has been reported that the coronavirus infection has neurological manifestations including pupillary involvement.[1,2] The cases of two patients with Adie’s tonic pupil 10–15 days after they had BNT16b2b mRNA (Pfizer, BioNTech, Germany) vaccine were reported. One of them had Holmes-Adie syndrome.[3,4] In this case report, we aim to describe two patients who are a married couple with possible coronavirus BNT16b2b mRNA vaccine (Pfizer, BioNTech, Germany)-related Holmes-Adie syndrome.

Absence of pupillary reflex dilation in response to a laryngeal test stimulus may predict safe tracheal extubation in anesthetized children.

Absence of pupillary reflex dilation in response to a laryngeal test stimulus may predict safe tracheal extubation in anesthetized children.

#2851 Effects of dialysis on various microcirculatory beds in end-stage kidney disease (ESKD): a systematic review and meta-analysis

Abstract Background and Aims Microcirculatory dysfunction is common in ESKD-patients and may play a pivotal role in their cardiovascular burden. Besides traditional and chronic-kidney-disease (CKD)-specific risk factors, dialysis itself might contribute to the dysfunction of the microcirculation (MC). Although an intradialytic fall in systemic blood pressure (BP) may directly influence the microcirculatory perfusion, vascular beds in different organs may not react uniformly. This systematic review and meta-analysis evaluated the acute impact of hemodialysis (HD) and hemodiafiltration (HDF) on the MC in various vascular beds. Methods Pubmed and Embase databases were systematically explored until June 2023 by two independent researchers. All observational and interventional studies in ESKD patients that reported dialysis-induced alterations of the MC, measured at the cutaneous, sublingual, retinal, muscle or coronary beds were eligible. Dialysis-induced changes were extracted and pooled, using a fixed-effects meta-analysis when the studies were reasonably homogeneous in terms of outcomes and methodology. Results 17 Studies with 493 participants were included. Virtually all patients (99.8%) were treated with HD. No eligible studies on coronary or muscle MC were identified. Cutaneous MC was investigated in 7 studies, showing a mean reduction in transcutaneous oxygen pressure of −7.9 mmHg (95% CI −10.5 to –5.3, n = 4 studies) and a mean reduction in blood flow of −0.9 arbitrary units (95% CI −1.2 to −0.6, n = 3 studies). Cutaneous vasoreactivity was diminished in 2 out of 3 studies (reactive maximum microvascular hyperemia: −36% (p &amp;lt; 0.05); time to reach baseline skin temperature after standardized cooling: 65.6 seconds (p-value not reported); vs. no significant change in post-ischemic maximal flow (2.5, p = not significant (N.S.)). Sublingual MC was assessed in 3 studies, showing a mean decrease in microvascular flow index of −0.6 in small microvessels (vessel diameter (VD) &amp;lt;20-25 µm, 95% CI −1.0 to −0.2, n = 3 studies), but no significant change in proportion of perfused vessels (−0.5%, 95% CI −1.2 to 0.2, n = 2 studies). One study showed a significant reduction in sublingual perfused vessel density after treatment (VD &amp;lt;20 µm: −1.6 ± 3.1, p &amp;lt; 0.05; VD &amp;gt;20 µm: −0.6 ± 1.1, p &amp;lt; 0.05), whereas total vessel density was unaffected in another study (VD &amp;lt;20 µm: 0.5, p = N.S.). Retinal MC was investigated in 7 studies, showing that the perfused vessel density (PVD) remained unchanged in both the superficial and deep capillary plexus (PVD SCP −0.48, 95% CI (−0.99; 0.03); PVD DCP −0.48, 95% CI (−1.18; 0.23), n = 4 studies). One study reported a decreased PVD at the outer retina (−1.3 ± 5.7, p &amp;lt; 0.05), while conflicting results were observed in 2 studies (0.1, p = N.S.; vs. −2.9 ± 4.3, p &amp;lt; 0.001), reporting the PVD at the choriocapillaris level. One study found no change in retinal blood flow (0.4, p = N.S.). With regard to vessel diameter changes, an increase in retinal venular diameter was observed in 3 studies (retinal venular diameter: 11.2 µm, p = 0.002; central retinal vein equivalent: 12.7 µm, p &amp;lt; 0.001; retinal vessel diameter: 4.4, p &amp;lt; 0.01), and one study described impaired venular dilatation in response to flicker light (−4.0, p = 0.04). Conclusions Hemodialysis induces microvascular dysfunction in different organs, but its impact varies between vascular beds. Microvascular perfusion was most significantly impaired in the cutaneous and sublingual regions, whereas the retinal microcirculatory perfusion remained unaltered. Literature on the effect of hemodiafiltration on the MC is lacking.

The role of constitutive properties on the longitudinal compressive strength of composites

The longitudinal compressive strength of fibre-reinforced composites is often a limiting factor for structural design. This paper uses micromechanical finite-element analyses to examine how the constitutive properties of the matrix, fibres, and interface affect the composite’s strength. For a typical carbon/epoxy composite, the matrix shear strength has a larger effect than the modulus; a linear-elastic perfectly-plastic approximation of the matrix shear curve may overestimate the composite’s strength by over 15%. A pressure-dependent and dilatant matrix plasticity response may strengthen the composite by 30%, considering current uncertainties in friction and dilation angles of epoxy matrices. The finite shear modulus of carbon fibres may weaken the composite by more than 10%. Considering a cohesive interface using traction–separation laws significantly affects the predicted response of the composite, even for interfaces stronger than the matrix. Opportunities for improving the characterisation, modelling and performance of the constituents in terms of matrix plasticity, fibre shear modulus, and interface response are discussed.