Changes In Relative Concentrations Research Articles

Effect of intermittent hypoxia on glucose tolerance in adults with type 2 diabetes

Hypoxia stimulates glucose uptake through an insulin-independent pathway. The purpose of this single-blind randomized study was to determine the acute effect of intermittent hypoxia, consisting of alternating short bouts of breathing hypoxic and normoxic air, on glucose and insulin concentrations during an oral glucose tolerance test in adults with type 2 diabetes. It was hypothesized that intermittent hypoxia would attenuate the increase in glucose and insulin concentrations during an oral glucose tolerance test. Six adults with type 2 diabetes (5 men, age: 51±15 years, HbA1c: 7.3±1.5%) visited the laboratory on two occasions. On both visits, a 2-hour oral glucose tolerance test was performed, with venous blood samples collected 0, 30, 60, 90, and 120 min after ingestion of a high-glucose drink. Following ingestion of the drink, participants were exposed to either an intermittent hypoxia (IH) protocol, consisting of eight 4-min hypoxic cycles at a targeted arterial oxygen saturation of 80% interspersed with breathing room air to resaturation, or an intermittent normoxia (IN) protocol consisting of eight 4-min normoxic cycles interspersed with breathing room air. By design, oxygen saturation was lower during intermittent hypoxia than intermittent normoxia (81±3 vs. 97±1%, p<0.01). Relative changes in plasma glucose concentrations in response to the oral glucose tolerance tests were not different between conditions (IH vs. IN: 30: 42±15 vs. 35±15; 60: 57±26 vs. 65±30; 90: 73±32 vs. 88±30; and 120: 78±26 vs. 83±29 mg/dl, interaction effect: p=0.13). Similarly, the relative changes in insulin concentrations in response to the oral glucose tolerance tests were not different between conditions (IH vs. IN: 30: 14±17 vs. 25±17; 60: 42±36 vs. 48±35; 90: 70±58 vs. 86±60; and 120: 103±72 vs. 125±94 ulU/ml, main effect for condition: p=0.12). While these preliminary results did not reach statistical significance, the observed trends for reduced glucose concentrations in combination with lower insulin concentrations during intermittent hypoxia suggest that short bouts of hypoxia improve glucose tolerance by stimulating glucose uptake independently from the action of insulin. Data from a larger sample size of adults with type 2 diabetes are needed to confirm these preliminary findings. None. 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.

Molecular-level explanation of interactions of random and block polycarboxylic acid dispersants with bituminous coal in coal–water slurry through experiments and simulations

The adsorption conformations of random-structure polycarboxylic acid (PCR) and block-structure polycarboxylic acid (PCB) on coal surfaces were analyzed from a microscopic perspective. This analysis involved a combination of molecular dynamics (MD) simulations and experiments. The saturation adsorption amount of PCB was found to be significantly much larger than that of PCR. Additionally, observations from the contact angle and X-ray photoelectron spectroscopy confirmed that PCB exhibited superior wetting performance on coal compared to PCR and had a greater adsorption layer thickness. The relative concentration changes and the mean square displacement (MSD) of water indicate that the better adsorption of PCB on the coal surface makes the water molecules more evenly distributed, which improves hydration, increases the thickness of the “adsorption layer”, and enhances the mobility of water molecules. The interaction energy suggests the block structure of PCB is more favorable for molecular extension due to its well-defined structure. This provides a theoretical and experimental basis for expanding the molecular sequence structure design of polycarboxylic acid dispersants.

Prefrontal Cortex Activity During Gait in People With Persistent Symptoms After Concussion

Background Concussions result in transient symptoms stemming from a cortical metabolic energy crisis. Though this metabolic energy crisis typically resolves in a month, symptoms can persist for years. The symptomatic period is associated with gait dysfunction, the cortical underpinnings of which are poorly understood. Quantifying prefrontal cortex (PFC) activity during gait may provide insight into post-concussion gait dysfunction. The purpose of this study was to explore the effects of persisting concussion symptoms on PFC activity during gait. We hypothesized that adults with persisting concussion symptoms would have greater PFC activity during gait than controls. Within the concussed group, we hypothesized that worse symptoms would relate to increased PFC activity during gait, and that increased PFC activity would relate to worse gait characteristics. Methods The Neurobehavior Symptom Inventory (NSI) characterized concussion symptoms. Functional near-infrared spectroscopy quantified PFC activity (relative concentration changes of oxygenated hemoglobin [HbO2]) in 14 people with a concussion and 25 controls. Gait was assessed using six inertial sensors in the concussion group. Results Average NSI total score was 26.4 (13.2). HbO2 was significantly higher (P = .007) for the concussed group (0.058 [0.108]) compared to the control group (−0.016 [0.057]). Within the concussion group, HbO2 correlated with NSI total symptom score (ρ = .62; P = .02), sagittal range of motion (r = .79; P = .001), and stride time variability (r = −.54; P = .046). Conclusion These data suggest PFC activity relates to symptom severity and some gait characteristics in people with persistent concussion symptoms. Identifying the neurophysiological underpinnings to gait deficits post-concussion expands our knowledge of motor behavior deficits in people with persistent concussion symptoms.

Cerebral oxygenation and perfusion kinetics monitoring of military aircrew at high G using novel fNIRS wearable system.

Real-time physiological episode (PE) detection and management in aircrew operating high-performance aircraft (HPA) is crucial for the US Military. This paper addresses the unique challenges posed by high acceleration (G-force) in HPA aircrew and explores the potential of a novel wearable functional near-infrared spectroscopy (fNIRS) system, named NIRSense Aerie, to continuously monitor cerebral oxygenation during high G-force exposure. The NIRSense Aerie system is a flight-optimized, wearable fNIRS device designed to monitor tissue oxygenation 13-20 mm below the skin's surface. The system includes an optical frontend adhered to the forehead, an electronics module behind the earcup of aircrew helmets, and a custom adhesive for secure attachment. The fNIRS optical layout incorporates near-distance, middle-distance, and far-distance infrared emitters, a photodetector, and an accelerometer for motion measurements. Data processing involves the modified Beer-Lambert law for computing relative chromophore concentration changes. A human evaluation of the NIRSense Aerie was conducted on six subjects exposed to G-forces up to +9 Gz in an Aerospace Environmental Protection Laboratory centrifuge. fNIRS data, pulse oximetry, and electrocardiography (HR) were collected to analyze cerebral and superficial tissue oxygenation kinetics during G-loading and recovery. The NIRSense Aerie successfully captured cerebral deoxygenation responses during high G-force exposure, demonstrating its potential for continuous monitoring in challenging operational environments. Pulse oximetry was compromised during G-loading, emphasizing the system's advantage in uninterrupted cerebrovascular monitoring. Significant changes in oxygenation metrics were observed across G-loading levels, with distinct responses in Deoxy-Hb and Oxy-Hb concentrations. HR increased during G-loading, reflecting physiological stress and the anti-G straining maneuver. The NIRSense Aerie shows promise for real-time monitoring of aircrew physiological responses during high G-force exposure. Despite challenges, the system provides valuable insights into cerebral oxygenation kinetics. Future developments aim for miniaturization and optimization for enhanced aircrew comfort and wearability. This technology has potential for improving anti-G straining maneuver learning and retention through real-time cerebral oxygenation feedback during centrifuge training.

CONCENTRATION PROCESSES IN THE RETAIL AND MEAT PROCESSING INDUSTRY IN POLAND AND COMPETITIVE RELATIONSHIPS IN THE FOOD CHAIN

The study investigates the consolidation of Poland’s food retail and meat processing industry from 2010 to 2022. The aim was to assess the relative changes in concentration in these two sectors and to determine whether these processes affected competitive conditions in the food chain. For this purpose, the k-firm concentration ratio (CRk) and HHI index were estimated using Central Statistical Office data supplemented by revenue data for Poland’s largest meat processing and food retail companies. The research reveals a notable trend of mergers and acquisitions among food retail entities. As a result, the share of the top four retailers (CR4) increased from 25% in 2010 to 46% in 2022, and the market moved from a highly competitive to loose oligopoly. At the same time, the concentration of the meat industry increased, but to a lesser extent – CR4 in 2022 reached 33%. This would indicate that food retail firms’ bargaining power towards meat industry firms has increased. However, given the economic potential of firms, there is a slight improvement in the meat industry’s position vis-à-vis food retail. The concentration in the latter has been growing steadily, nevertheless, the sector itself has not been developing as dynamically as the meat processing one.

Evaluation of Salicylic Acid and Methyl Jasmonate as Elicitors in Phyllanthus acuminatus Hairy Roots by Non-Targeted Analysis Using High-Resolution Mass Spectrometry.

Phyllanthus acuminatus has been studied for its vast medical and industrial potential. Phytochemical investigations reveal that the genus is a rich source of lignans, flavonoids, phenolics, terpenoids, and other metabolites. However, the phytochemical profile elucidation of this species still needs further research. The use of eliciting compounds such as salicylic acid and methyl jasmonate has managed to increase the production of secondary metabolites in plant cell cultures. Hairy roots of Phyllanthus acuminatus were produced in 250 mL flasks with a 16 h light/8 h darkness photoperiod under diffused light with a culture time of four weeks. The elicitors salicylic acid and methyl jasmonate were tested in 50 μM and 200 μM concentrations. Non-targeted analysis was done for the different treatments using HR-MS. Identified metabolites were grouped in phenylpropanoids, phenols, and mucic acids, and statistical analysis of relative concentrations was achieved. A significant change in phenols' relative concentrations appeared in the elicitations with salicylic acid. Because of the elicitation treatment, specific compounds increased their concentrations, some of which have known pharmacological effects and are used in treating chronic diseases. The best elicitation treatment was salicylic acid 50 μM as it increased by more than 100% the general content of phenols and phenylpropanoid derivates and triplicates the concentration of mucic acid derivates in treated hairy root extracts. The application of non-targeted analysis showed interesting changes in phytochemical concentration due to elicitation in Phyllanthus acuminatus hairy roots.

Quantifying tissue properties and absolute hemodynamics using coherent spatial imaging.

Measuring hemodynamic function is crucial for health assessment. Optical signals provide relative hemoglobin concentration changes, but absolute measurements require costly, bulky technology. Speckleplethysmography (SPG) uses coherent light to detect speckle fluctuations. Combining SPG with multispectral measurements may provide important physiological information on blood flow and absolute hemoglobin concentration. To develop an affordable optical technology to measure tissue absorption, scattering, hemoglobin concentrations, tissue oxygen saturation (), and blood flow. We integrated reflectance spectroscopy and laser speckle imaging to create coherent spatial imaging (CSI). CSI was validated against spatial frequency domain imaging (SFDI) using phantom-based measurements. In vivo arterial and venous occlusion experiments compared CSI with diffuse optical spectroscopy/diffuse correlation spectroscopy (DOS/DCS) measurements. CSI and SFDI agreed on tissue absorption and scattering in phantom tests. CSI and DOS/DCS showed similar trends and agreement in arterial occlusion results. During venous occlusion, both uncorrected and corrected blood flow decreased with increasing pressure, with an difference in overall blood flow decrease between the methods. CSI and DOS/DCS data showed expected hemoglobin concentrations, , and blood flow trends. CSI provides affordable and comprehensive hemodynamic information. It can potentially detect dysfunction and improve measurements, such as blood pressure, , and metabolism.

Ag-TiO2 for Efficient Methylene Blue Photodegradation Under Visible Light Irradiation

Photocatalysis is one of the environmentally friendly methods for degrading down wastewater contamination. TiO2 as one of the photocatalyst material is claimed can enhance the photocatalytic activity much better, if the band gap energy is reduced. In order to reduce the bandgap energy of TiO2, the novel in this research is that the temperature variations over a 24-hour period at 100 °C, 120 °C, 140 °C, and 160 °C in hydrothermal process to synthesize the photocatalyst material with Ag-doped. Diffraction patterns of Ag-TiO2 show that all sample have tetragonal crystal structure and an anatase phase which also has excellent crystallinity. Some of the nanoparticles on the surface of Ag-TiO2 have a consistent morphology, while other particles are formed irregularly. According to the DRS UV-Vis result, bandgap energy reduced as temperature increased (Eg = 3.2 eV to 2.32 eV). The results from PL Ag-TiO2 160 have the lowest intensity, which indicates a low rate of electron-hole recombination. The Ag-TiO2 160 sample produced the best photocatalytic activity, according to the results of the MB degradation test, with a relative change in concentration of 92.98% for 2 h under visible light. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Serial high-sensitivity troponin-I and long-term risk of myocardial infarction and coronary revascularization in subjects with suspected acute coronary syndrome

Abstract Background Serial high-sensitivity troponin-I (hsTnI) concentrations are associated with mortality in individuals with suspected acute coronary syndrome. However, their relation to myocardial infarction and revascularization events is unknown. Purpose To determine short- and long-term risks of myocardial infarction and revascularization (PCI or CABG) according to hsTnI concentrations and their changes from baseline, in patients with suspected acute coronary syndrome. Methods Through Danish national registries, we identified subjects who underwent two hsTnI measurements (Siemens TnI Flex® Reagent, 99th percentile upper reference limit, 45 ng/l) separated by 1-7 hours, during hospitalization for myocardial infarction, unstable angina, observation for suspected myocardial infarction, or chest pain from 2012 through 2019. Individuals were stratified according to their hsTnI concentration pattern (main groups: normal, rising, persistently elevated, or falling) and the magnitude of hsTnI concentration change (secondary groups: <20%, >20 to 50%, or >50% in either direction). We calculated standardized absolute and relative risks of myocardial infarction and coronary revascularization using multivariable logistic regression with average treatment effect modeling, a method that ensures equal distribution of factors that may affect the risk of outcomes across the various groups of interest. Results A total of 20,609 individuals were included of whom 22.4% were discharged with a diagnosis of myocardial infarction, 4.8% with unstable angina, and 72.8% with observation for suspected myocardial infarction or chest pain. Median age was 63.2 years, and 53.1% were male. Considering known cardiovascular disease, 21.3% had coronary artery disease, 7.0% had undergone prior PCI or CABG, 8.1% had heart failure, and 10.7% had atrial fibrillation or flutter. The standardized risk of being diagnosed with myocardial infarction was lowest in subjects with two normal hsTnI values and highest in those with persistently elevated concentrations. Within each main group, the likelihood of being diagnosed with myocardial infarction generally appeared to increase with more pronounced hsTnI changes. The standardized risk of undergoing coronary revascularization mimicked this pattern, although among persons with two elevated hsTnI levels, the long-term-risk was not influenced by relative concentration changes. The findings are summarized in the Figure. Conclusions Among individuals with suspected acute coronary syndrome, those with a persistently elevated hsTnI concentration consistently had the highest risk of being diagnosed with myocardial infarction and undergoing coronary revascularization. The risk of these outcomes was, for the most part, also positively associated with the magnitude of hsTnI change.Figure

An Optical Micro/Nano Fiber Sensor for Monitoring Respiration

In the field of clinical medicine, the real-time monitoring of carbon dioxide (CO2) gas exhaled by the human body is of great significance. At present, the detection devices on the market mainly work by sucking a small amount of gas from the nasal cavity into the detection device, and they present some problems such as overly long sampling tubes, easy blockage or distortion, and an abnormal gas dispersion. In this paper, a micro/nano optical fiber sensor that can directly detect respiration is proposed and is characterized by the relative change in CO2 concentration. The measurement is achieved by using the principle of high evanescent field absorption, and the operating band is 2.004 μm. The sensing effects of micro/nano fibers with different diameters are compared, and the experiment proves that a micro/nano fiber with a diameter of 1 μm can be measured. The light intensity change over 30 s was measured, and the breathing rate was 10–11 times/min. The sensor can achieve a rapid real-time response to CO2 gas detection and is small in size, low-cost, and easy to replace. It has a great application potential in clinical scenarios such as in gastrointestinal endoscopes that require real-time monitoring of human respiration.

Elucidation of the effects of autochthonous starter on nitrogen-containing compounds during fermentation of Yujiangsuan by metabolomics.

To understand the role of microorganisms in nitrogen (N)-containing compound changes during the processing of Yujiangsuan by autochthonous starter cultures, the GC-TOF-MS-based metabolomics method was adopted to investigate the effects of Weissella cibaria and Lactobacillus plantarum. The results demonstrated that inoculation of autochthonous strains led to differential metabolites, such as fatty acids, organic oxygen compounds, and carboxylic acids on day 4 to day 12 of fermentation. The N-containing compounds under the inoculated fermentation group showed a faster relative concentration change. Nucleotide metabolism and arginine and proline metabolism exerted an influence on the formation of N-containing compounds. Apart from that, the effect of W. cibaria and L. plantarum on the hydrolysis of macromolecules was the main factor causing differences in major N-containing compounds.

Multi-Method Quantification of Acetyl-Coenzyme A and Further Acyl-Coenzyme A Species in Normal and Ischemic Rat Liver.

Thioesters of coenzyme A (CoA) carrying different acyl chains (acyl-CoAs) are central intermediates of many metabolic pathways and donor molecules for protein lysine acylation. Acyl-CoA species largely differ in terms of cellular concentrations and physico-chemical properties, rendering their analysis challenging. Here, we compare several approaches to quantify cellular acyl-CoA concentrations in normal and ischemic rat liver, using HPLC and LC-MS/MS for multi-acyl-CoA analysis, as well as NMR, fluorimetric and spectrophotometric techniques for the quantification of acetyl-CoAs. In particular, we describe a simple LC-MS/MS protocol that is suitable for the relative quantification of short and medium-chain acyl-CoA species. We show that ischemia induces specific changes in the short-chain acyl-CoA relative concentrations, while mild ischemia (1-2 min), although reducing succinyl-CoA, has little effects on acetyl-CoA, and even increases some acyl-CoA species upstream of the tricarboxylic acid cycle. In contrast, advanced ischemia (5-6 min) also reduces acetyl-CoA levels. Our approach provides the keys to accessing the acyl-CoA metabolome for a more in-depth analysis of metabolism, protein acylation and epigenetics.

Review of recent advances in frequency-domain near-infrared spectroscopy technologies [Invited

Over the past several decades, near-infrared spectroscopy (NIRS) has become a popular research and clinical tool for non-invasively measuring the oxygenation of biological tissues, with particular emphasis on applications to the human brain. In most cases, NIRS studies are performed using continuous-wave NIRS (CW-NIRS), which can only provide information on relative changes in chromophore concentrations, such as oxygenated and deoxygenated hemoglobin, as well as estimates of tissue oxygen saturation. Another type of NIRS known as frequency-domain NIRS (FD-NIRS) has significant advantages: it can directly measure optical pathlength and thus quantify the scattering and absorption coefficients of sampled tissues and provide direct measurements of absolute chromophore concentrations. This review describes the current status of FD-NIRS technologies, their performance, their advantages, and their limitations as compared to other NIRS methods. Significant landmarks of technological progress include the development of both benchtop and portable/wearable FD-NIRS technologies, sensitive front-end photonic components, and high-frequency phase measurements. Clinical applications of FD-NIRS technologies are discussed to provide context on current applications and needed areas of improvement. The review concludes by providing a roadmap toward the next generation of fully wearable, low-cost FD-NIRS systems.

Improving Surface Wear Resistance of Polyimide by Inserting KH550 Grafted GO.

To improve the wear resistance of polyimide (PI), surface modification was developed. In this study, the tribological properties of graphene (GN), graphene oxide (GO), and KH550-grafted graphene oxide (K5-GO) modified PI were evaluated by molecular dynamics (MD) at the atomic level. The findings indicated that the addition of nanomaterials can significantly enhance the friction performance of PI. The friction coefficient of PI composites decreased from 0.253 to 0.232, 0.136, and 0.079 after coating GN, GO and K5-GO, respectively. Among them, the K5-GO/PI exhibited the best surface wear resistance. Importantly, the mechanism behind the modification of PI was thoroughly revealed by observing the wear state, analyzing the changes of interfacial interactions, interfacial temperature, and relative concentration.

Decoding the physiological response of plants to stress using deep learning for forecasting crop loss due to abiotic, biotic, and climatic variables

This paper presents a simple method for detecting both biotic and abiotic stress in plants. Stress levels are measured based on the increase in nutrient uptake by plants as a mechanism of self-defense when under stress. A continuous electrical resistance measurement was used to estimate the rate of change of nutrients in agarose as the growth medium for Cicer arietinum (Chickpea) seeds. To determine the concentration of charge carriers in the growth medium, Drude’s model was used. For identifying anomalies and forecasting plant stress, two experiments were conducted and outliers were found in electrical resistance and relative changes in carrier concentration. Anomaly in the first iteration was detected by applying k-Nearest Neighbour, One Class Support Vector Machine and Local Outlier Factor in unsupervised mode on electrical resistance data. In the second iteration, the neural network-based Long Short Term Memory method was used on the relative change in the carrier concentration data. As a result of the change in resistance of growth media during stress, nutrient concentrations shifted by 35%, as previously reported. Farmers who cater to small communities around them and are most affected by local and global stress factors can use this method of forecasting.

Inflammation Biomarker Response to Oral 2-Hydroxybenzylamine (2-HOBA) Acetate in Healthy Humans.

Inflammation is associated with the formation of reactive oxygen species (ROS) and the formation of lipid-derived compounds, such as isolevuglandins (IsoLGs), malondialdehyde, 4-hydroxy-nonenal, and 4-oxo-nonenal. The most reactive of these are the IsoLGs, which form covalent adducts with lysine residues and other cellular primary amines leading to changes in protein function, immunogenicity, and epigenetic alterations and have been shown to contribute to a number of inflammatory diseases. 2-Hydroxybenzylamine (2-HOBA) is a natural compound found in buckwheat seeds and reacts with all IsoLG adducts preventing adduct formation with proteins and DNA. Therefore, 2-HOBA is well positioned as an agent for the prevention of inflammatory-prone diseases. In this study, we examined the potential beneficial effects of 2-HOBA on oxidative stress and inflammatory biomarkers in two cohorts of healthy younger and older adults. We utilized the Olink® targeted inflammation panel before and after an oral 15-day treatment regimen with 2-HOBA. We found significant relative changes in the plasma concentration of 15 immune proteins that may reflect the in vivo immune targets of 2-HOBA. Treatment of 2-HOBA resulted in significant increased levels of CCL19, IL-12β, IL-20Rα, and TNFβ, whereas levels of TWEAK significantly decreased. Ingenuity Pathway Analysis identified canonical pathways regulated by the differentially secreted cytokines, chemokines, and growth factors upon 2-HOBA treatment and further points to biofunctions related to the recruitment, attraction, and movement of different immune cell types. In conclusion, 2-HOBA significantly altered the protein biomarkers CCL19, IL-12β, IL-20Rα, TNFβ, and TWEAK, and these may be responsible for the protective effects of 2-HOBA against reactive electrophiles, such as IsoLGs, commonly expressed in conditions of excessive oxidative stress. 2-HOBA has a role as a IsoLG scavenger to proactively improve immune health in a variety of conditions.

A Unit Process Approach to Nontarget Screening of Organic Contaminants during Urine Treatment

Urine treatment has expanded over the past few decades; however, widespread implementation requires rigorous, generalizable comparisons between selective nutrient separation and organic compound mitigation. This study describes and demonstrates an enrichment ratio framework, defined as the relative concentration changes of nutrients (nitrogen or phosphorus) with organic compounds analyzed via high-resolution mass spectrometry. Nontarget analysis enabled comparison of the effects of urine treatment processes (e.g., ion exchange, freeze–thaw, activated carbon, struvite precipitation) on organic compounds. In total, we considered 14 treatment scenarios, including six unit processes for acidified urine and eight for hydrolyzed urine. Acidified and hydrolyzed urine were characterized longitudinally, and each of the two urine types remained stable in terms of the organic compound profile (>79% similarity) over several weeks. Unit processes with mean enrichment ratios (ER) that involved more than a 2-fold concentration change (ER > 2 or ER < 0.5) were considered high priority and were further separated into cases in which organic compounds were concentrated (ER > 2) or removed (ER < 0.5) for various unit processes. Whereas ER values are typically calculated only for compounds present in both the influent and effluent streams, we also analyzed compounds that were detected in only influent or only effluent added. Results from the target analysis of six compounds generally corroborated the nontarget results. Ultimately, our approach to simultaneously characterizing both nutrients and organic compounds through urine processing steps can inform and advance the implementation of urine resource recovery.

Serum concentrations of amino acids and tryptophan metabolites are affected by consumption of a light breakfast: a clinical intervention study in adults with overweight or obesity

BackgroundEpidemiological studies often investigate amino acids and their metabolites as biomarkers, but do not always consistently use fasting or non-fasting blood samples, or may lack information on the prandial status of the study participants. Since little information is available on the effects of the prandial status on many biomarkers, and since blood is typically sampled early in the day with participants in a fasting state or after having consumed a light meal in many trials, the main purpose of this study was to investigate the short-term effects of a light breakfast on serum concentrations of amino acids and related metabolites.MethodsBlood was collected from sixty-three healthy adults (36 women) in the fasting state and at set times for 120 min after intake of a light breakfast with low protein content (14 g protein, 2218 kJ). Relative changes in serum biomarker concentrations from fasting to postprandial serum concentrations were tested using T test.ResultsThe serum concentrations of 13 of the 20 measured amino acids were significantly changed 60 min following breakfast intake, with the most marked effects seen as increases in alanine (34%) and proline (45%) concentrations. The response did not reflect the amino acid composition of the breakfast. The concentrations of seven kynurenine metabolites were significantly decreased after breakfast.ConclusionConsumption of a light breakfast affected serum concentrations of several amino acids and related metabolites, underlining the importance of having information regarding the participants’ prandial state at the time of blood sampling in studies including these biomarkers.Trial registrationThis trial was registered at clinicaltrials.gov as NCT02350595 (registered January 2015).

A machine learning approach to address air quality changes during the COVID-19 lockdown in Buenos Aires, Argentina

Abstract. Having a prediction model for air quality at a low computational cost can be useful for research, forecasting, regulatory, and monitoring applications. This is of particular importance for Latin America, where rapid urbanization has imposed increasing stress on the air quality of almost all cities. In recent years, machine learning techniques have been increasingly accepted as a useful tool for air quality forecasting. Out of these, random forest has proven to be an approach that is both well-performing and computationally efficient while still providing key components reflecting the nonlinear relationships among emissions, chemical reactions, and meteorological effects. In this work, we employed the random forest methodology to build and test a forecasting model for the city of Buenos Aires. We used this model to study the deep decline in most pollutants during the lockdown imposed by the COVID-19 (COronaVIrus Disease 2019) pandemic by analyzing the effects of the change in emissions, while taking into account the changes in the meteorology, using two different approaches. First, we built random forest models trained with the data from before the beginning of the lockdown periods. We used the data to make predictions of the business-as-usual scenario during the lockdown periods and estimated the changes in concentrations by comparing the model results with the observations. This allowed us to assess the combined effects of the particular weather conditions and the reduction in emissions during the period when restrictions were in place. Second, we used random forest with meteorological normalization to compare the observational data from the lockdown periods with the data from the same dates in 2019, thus decoupling the effects of the meteorology from short-term emission changes. This allowed us to analyze the general effect that restrictions similar to those imposed during the pandemic could have on pollutant concentrations, and this information could be useful to design mitigation strategies. The results during testing showed that the model captured the observed hourly variations and the diurnal cycles of these pollutants with a normalized mean bias of less than 6 % and Pearson correlation coefficients of the diurnal variations between 0.64 and 0.91 for all the pollutants considered. Based on the random forest results, we estimated that the lockdown implied relative changes in concentration of up to −45 % for CO, −75 % for NO, −46 % for NO2, −12 % for SO2, and −33 % for PM10 during the strictest mobility restrictions. O3 had a positive relative change in concentration (up to an 80 %) that is consistent with the response in a volatile-organic-compound-limited chemical regime to the decline in NOx emissions. The relative changes estimated using the meteorological normalization technique show mostly smaller changes than those obtained by the random forest predictive model. The relative changes were up to −26 % for CO, up to −47 % for NO, −36 % for NO2, −20 % for PM10, and up to 27 % for O3. SO2 is the only species that had a larger relative change when the meteorology was normalized (up to 20 %). This points out the need for accounting not only for differences in emissions but also in meteorological variables in order to evaluate the lockdown effects on air quality. The findings of this study may be valuable for formulating emission control strategies that do not disregard their implication on secondary pollutants. We believe that the model itself can also be a valuable contribution to a forecasting system in the city and that the general methodology could also be easily applied to other Latin American cities as well. We also provide the first O3 and SO2 observational dataset in more that a decade for a residential area in Buenos Aires, and it is openly available at https://doi.org/10.17632/h9y4hb8sf8.1 (Diaz Resquin et al., 2021).

Near-Infrared Spectroscopy measurements are reliable for studying patellar bone hemodynamics and affected by venous occlusion, but not by skin compression

PurposeAccording to the homeostasis model, patellofemoral pain (PFP) results from disturbed homeostasis due to vascular insufficiency in the anterior knee. Near-Infrared Spectroscopy (NIRS) measures relative changes in concentrations (in µmol/cm2) of (de-)oxygenated hemoglobine (HHb and O2Hb). The aims were to: 1) investigate the characteristics of the NIRS signal derived from the patella during experiments affecting hemodynamics in healthy controls, and 2) determine the test–retest reliability of NIRS in positions clinically relevant for PFP patients.MethodsTwo experiments were conducted on 10 healthy controls and analysed using Student’s t-test. Reliability (ICC2,1) was evaluated for two activities (‘Prolonged Sitting’ and ‘Stair Descent’) in five PFP patients and 15 healthy controls, performed twice within five days.ResultsThe NIRS signal (HHb and O2Hb) showed a statistically significant increase (p < .001 – .002) on all optodes (30, 35, 40 mm) during ‘Venous Occlusion’ (M = 1.0 – 2.0), while it showed no statistically significant change (p = .075 – .61) during ‘Skin Compression’ (M = -0.9 – 0.9) on the 30 and 35 mm optode. Reliability of NIRS (HHb and O2Hb) ranged from moderate to almost perfect (ICC2,1 = .47 – .95) on the 30 mm optode for ‘Prolonged Sitting’, and from moderate to substantial (ICC2,1 = .50 – .68) on the 35 mm optode for ‘Stair Descent’.ConclusionsPatella NIRS measurements are affected by venous occlusion, but not by skin compression, and are sufficiently reliable as research application to compare real-time patellar bone hemodynamics. These insights may assist to improve effectiveness of evidence-based treatment strategies for PFP.Trial registrationISRCTN Trial Registration under number: 90377123.