Measurement Of Changes In Concentration Research Articles

Electrochemical Aptamer-Based Biosensors for Real-Time Monitoring of Biomarkers In Vivo

There is a need for bioanalytical sensors that operate reliably for real-time monitoring of biomarkers in vivo. To address this need, we have created a hybrid sensor integrating microneedle patches with aptamer-based electrochemical sensors for monitoring glucose and lactate in vivo. We have developed a series of quality control and programmable calibration curves for measuring concentration changes in vivo. Using these methods, we have been able to monitor both lactate and glucose simultaneously in the interstitial fluid of two live animal models. Our measurements are in excellent correlation with analysis performed on blood using gold standard laboratory techniques.

Metabolites, ions, and the mechanisms behind seasonal cold hardening of Pyrochroa coccinea (Pyrochroidae) larvae

The larvae of the black headed cardinal beetle Pyrochroa coccinea, overwinters under the bark of dead logs in northern European dioecious forests, and are thus exposed to temperatures below the melting point of their bodily fluids. Here we explore the mechanisms behind their seasonal cold hardening by characterising field samples collected monthly throughout the year. Both the lower lethal temperature and supercooling point dropped as much as 10℃ in the second half of November, reaching values around –15℃ by the beginning of December. This change was accompanied by a 320 mosmol/kg increase in hemolymph osmolality, which is a doubling compared to the summer levels. We used NMR metabolomics to identify and measure the absolute concentrations of the responsible cryoprotective C-H containing metabolites in the hemolymph. The largest increase was found to be in either glucose or trehalose, with an average total increase of 120 mM. Proline, alanine, and choline concentrations were found to increase by around 10 mM each. Contrarily, phosphocholine and phosphoethanolamine were halved, resulting in a total decrease of around 50 mM. These measurements were complemented with ion exchange chromatography measurements. This allowed us to account for all the osmotic pressure in the summer hemolymph, and the measured concentration changes explained as much as 40 % of the observed osmolality increase upon cold hardening. Preliminary results indicate that the remainder may be explained by non-colligative protein contributions.

Development of a Contactless Conductivity Sensor in Flowing Micro Systems for Cerium Nitrate

Impedance spectroscopy has a high potential to detect chemical reactions in flowing systems. In this work, the approach using impedance spectroscopy as a possible analytical tool for a continuous hydrothermal syntheses (CHTS) is presented. With the CHTS-process, it is possible to produce metalloxide nanoparticles with a close particle size distribution and specific surface properties. For this, it is necessary to evaluate the electrode geometry, frequency and other factors influencing the impedance with respect to concentration measurements. In case of frequency-sweep measurements possible electrode geometries for C4D-Sensors (capacitively coupled contactless conductivity detection) are evaluated. Then distinguishability and reproducibility are tested applying titration measurements to show the ability for concentration detection in constant flow systems. The possibility to measure concentration changes in flowing systems in a reproducible and fast manner as well as with high distinguishability for the test solution cerium nitrate will be presented. Furthermore, the major influencing-factors like electrode geometry, frequency etc. could be determined. It has been shown that with increasing electrode spacing and electrode width, the distinguishability of the concentrations increases and shifts them to lower frequencies.

Identification and profiling of Trichinella spiralis circulating antigens and proteins in sera of mice with trichinellosis.

Trichinellosis is a zoonotic disease caused by the ingestion of the Trichinella nematode. With a worldwide incidence of approximately 10,000 cases per year, Trichinella spiralis is responsible for most human infections. There are no specific signs or symptoms of this parasitic infection. Muscle biopsy is the gold diagnostic standard for trichinellosis, but the technique is invasive and unable to detect the early stage of infection. Although immunodiagnostics are also available, antibody detection usually occurs after 3 weeks and prolonged up to 19 years after the acute phase. Therefore, additional diagnostic biomarkers must be identified to improve trichinellosis diagnosis. This study aimed to measure concentration changes in mouse serum proteins prior to T. spiralis infection and 2, 4 and 8 weeks after infection, and to identify T. spiralis circulating proteins and antigens using mass spectrometry-based proteomics. Mouse muscle-related proteins including inter-alpha-trypsin inhibitor heavy chain H2, a protein involved in the response to muscle tissue damage, were up-regulated in mouse sera during the T. spiralis larvae invasion. Additionally, 33 circulatory parasite proteins were identified in infected mouse sera. Notably, T. spiralis long-chain fatty acid transport protein 1 could be detected in the early stage of infection and peroxidasin-like protein was identified 2, 4 and 8 weeks after infection. Seventeen T. spiralis circulating antigens were detected in mouse immune complexes, with PX domain protein being found 2, 4 and 8 weeks after infection. Because peroxidasin-like protein and PX domain protein were detected at all post-infection time points, sequence alignments of these proteins were performed, which showed they are conserved among Trichinella spp. and have less similarity to the human and murine sequences. Integrative analysis of T. spiralis biomarkers throughout the course of infection may reveal additional diagnostic targets to improve early diagnosis of trichinellosis.

Electrohydrodynamically enhanced mass transfer in a wetted-wall column

Intensified heat and mass transfer due to electrohydrodynamically (EHD) induced turbulence in wet electrostatic precipitators allows for versatile new opportunities and applications in the process industry. In order to demonstrate its feasibility and provide primary experimental data, a combination of a wetted- wall column and an electrostatic precipitator was tested experimentally. This investigation includes the variation over a multitude of different operating and design parameters, such as the magnitude and polarity of operating voltage, shape of the discharge electrode, flow velocity and flow configuration, i.e. counter-current vs. parallel flow. The results are presented as mass transfer coefficients, determined by measuring concentration changes of two different substance systems, i.e. the evaporation of water in air and the absorption of vaporized acetic acid in a highly alkaline aqueous solution.The study has shown that mass transfer can be enhanced significantly by EHD effects in the gas phase. The enhancement factor ranges between three to eight, depending on the operating conditions and the choice of discharge electrode design. These findings are complemented by a feasibility assessment based on the energy consumption, showing that this technique will work best when using non-symmetrical discharge electrode designs.

Hemodynamic changes associated with common EEG patterns in critically ill patients: Pilot results from continuous EEG-fNIRS study

Functional near-infrared spectroscopy (fNIRS) is currently the only non-invasive method allowing for continuous long-term assessment of cerebral hemodynamic. We evaluate the feasibility of using continueous electroencephalgraphy (cEEG)-fNIRS to study the cortical hemodynamic associated with status epilepticus (SE), burst suppression (BS) and periodic discharges (PDs). Eleven adult comatose patients admitted to the neuroICU for SE were recruited, and cEEG-fNIRS monitoring was performed to measure concentration changes in oxygenated (HbO) and deoxygenated hemoglobin (HbR). Seizures were associated with a large increase HbO and a decrease in HbR whose durations were positively correlated with the seizures' length. Similar observations were made for hemodynamic changes associated with bursts, showing overall increases in HbO and decreases in HbR relative to the suppression periods. PDs were seen to induce widespread HbO increases and HbR decreases. These results suggest that normal neurovascular coupling is partially retained with the hemodynamic response to the detected EEG patterns in these patients. However, the shape and distribution of the response were highly variable. This work highlighted the feasibility of conducting long-term cEEG-fNIRS to monitor hemodynamic changes over a large cortical area in critically ill patients, opening new routes for better understanding and management of abnormal EEG patterns in neuroICU.

High tolerance to instrument drifts by differential chemical isotope labeling LC-MS: A case study of the effect of LC leak in long-term sample runs on quantitative metabolome analysis.

Metabolomics study of a biological system often involves the analysis of many comparative samples over a period of several days or weeks. This process of long-term sample runs can encounter unexpected instrument drifts such as small leaks in liquid chromatography-mass spectrometry (LC-MS), degradation of column performance, and MS signal intensity change. A robust analytical method should ideally tolerate these instrumental drifts as much as possible. In this work, we report a case study to demonstrate the high tolerance of differential chemical isotope labeling (CIL) LC-MS method for quantitative metabolome analysis. In a study of using a rat model to examine the metabolome changes during rheumatoid arthritis (RA) disease development and treatment, over 468 samples were analyzed over a period of 15 days in three batches. During the sample runs, a small leak in LC was discovered after a batch of analyses was completed. Reanalysis of these samples was not an option as sample amounts were limited. To overcome the problem caused by the small leak, we applied a method of retention time correction to the LC-MS data to align peak pairs from different runs with different degrees of leak, followed by peak ratio calculation and analysis. Herein, we illustrate that using 12 C-/13 C-peak pair intensity values in CIL LC-MS as a measurement of concentration changes in different samples could tolerate the signal drifts, while using the absolute intensity values (ie, 12 C-peak as in conventional LC-MS) was not as reliable. We hope that the case study illustrated and the method of overcoming the small-leak-caused signal drifts can be helpful to others who may encounter this kind of situation in long-term sample runs.

Characterization of Li+ and Na+ Insertion into Sodium Titanium Phosphate

Due to their high energy density, lithium-ion batteries based on organic electrolytes are ubiquitous in applications such as consumer electronics. However, high capital costs and flammability of the electrolyte have limited their use in residential or grid storage. An alternative involves replacing the organic solvent-based electrolytes with aqueous electrolytes and using electrochemical couples that operate within the water electrolysis stability window. Aqueous electrolytes have several advantages, such as ease of manufacturing, greater safety, and more cell design flexibility due to the higher conductivity compared to organic electrolytes 1.In addition to aqueous Li-ion batteries, aqueous Na-ion batteries have attracted significant interest due to the increased availability of Na on earth and further cost reductions1,2. Furthermore, aqueous commercial batteries using electrolytes containing both Li+ and Na+ exist. For example, one such battery using a lithium manganese oxide cathode, a sodium titanium phosphate (NTP) anode, and a Li2SO4/Na2SO4 electrolyte has been commercialized by companies such as Aquion Energy and BenAn Energy2. Despite the advantages described previously, the operating voltage window of aqueous electrolytes is smaller than that of its organic counterparts. In addition, insertion behavior in aqueous electrolytes is more complex than what is observed in organic electrolyte systems3. This can be further complicated when using electrolytes with more than one cation4,5. One such example involves the insertion of Li+ and Na+ into NTP. In electrolytes where Na+ is the only cation, a single redox couple attributed to Na+ insertion is observed on CV experiments. Meanwhile, when both Li+ and Na+ are present, insertion of both cations occurs, with equilibration occurring after 10 CV cycles4. Despite this interesting behavior, little is known as to how the Li2SO4/Na2SO4 ratio affects the insertion behavior of NTP.In this work, the effect of Li2SO4 and Na2SO4 concentration in the insertion behavior will be characterized using CV and galvanostatic cycling with ion monitoring. CV experiments will be used to characterize the relative extent of insertion for both Li+ and Na+ and the insertion potentials. Meanwhile, galvanostatic cycling will be used to assess the connection between the CV results and charge/discharge plateaus observed under different Li2SO4/Na2SO4 ratios. In addition, ion monitoring will be performed every 50 cycles at relevant conditions (bottom and top of charge and intermediate points) to measure concentration changes in the electrolyte concentrations. Furthermore, galvanostatic intermittent titration cycles will be incorporated into the cycling regime to characterize the effect of concentration in the open circuit voltage (OCV) and resistance, as well as exploring changes in these variables as a function of cycling.

Measurement of Multi Ion Transport through Human Bronchial Epithelial Cell Line Provides an Insight into the Mechanism of Defective Water Transport in Cystic Fibrosis.

We measured concentration changes of sodium, potassium, chloride ions, pH and the transepithelial potential difference by means of ion-selective electrodes, which were placed on both sides of a human bronchial epithelial 16HBE14σ cell line grown on a porous support in the presence of ion channel blockers. We found that, in the isosmotic transepithelial concentration gradient of either sodium or chloride ions, there is an electroneutral transport of the isosmotic solution of sodium chloride in both directions across the cell monolayer. The transepithelial potential difference is below 3 mV. Potassium and pH change plays a minor role in ion transport. Based on our measurements, we hypothesize that in a healthy bronchial epithelium, there is a dynamic balance between water absorption and secretion. Water absorption is caused by the action of two exchangers, Na/H and Cl/HCO3, secreting weakly dissociated carbonic acid in exchange for well dissociated NaCl and water. The water secretion phase is triggered by an apical low volume-dependent factor opening the Cystic Fibrosis Transmembrane Regulator CFTR channel and secreting anions that are accompanied by paracellular sodium and water transport.

Cognitive Enhancement by Transcranial Photobiomodulation Is Associated With Cerebrovascular Oxygenation of the Prefrontal Cortex.

Transcranial infrared laser stimulation (TILS) is a novel, safe, non-invasive method of brain photobiomodulation. Laser stimulation of the human prefrontal cortex causes cognitive enhancement. To investigate the hemodynamic effects in prefrontal cortex by which this cognitive enhancement occurs, we used functional near-infrared spectroscopy (fNIRS), which is a safe, non-invasive method of monitoring hemodynamics. We measured concentration changes in oxygenated and deoxygenated hemoglobin, total hemoglobin and differential effects in 18 healthy adults during sustained attention and working memory performance, before and after laser of the right prefrontal cortex. We also measured 16 sham controls without photobiomodulation. fNIRS revealed large effects on prefrontal oxygenation during cognitive enhancement post-laser and provided the first demonstration that cognitive enhancement by transcranial photobiomodulation is associated with cerebrovascular oxygenation of the prefrontal cortex. Sham control data served to rule out that the laser effects were due to pre-post task repetition or other non-specific effects. A laser-fNIRS combination may be useful to stimulate and monitor cerebrovascular oxygenation associated with neurocognitive enhancement in healthy individuals and in those with prefrontal hypometabolism, such as in cognitive aging, dementia and many neuropsychiatric disorders.

Evolving banking market structure in Oman: should CBO approve the mergers?

PurposeIn 2013-2014, Bank Muscat and National Bank of Oman requested a merger and Bank Sohar and Bank Dhofar lodged a similar request. This paper aims to investigate the shape of the market structure, and it tries to answer whether approving such requests is good for the industry, economy and society.Design/methodology/approachThe study examines the market structure of Oman Banking Industry, and it also presents the shape of the market structure if there had been an approval for these mergers’ requests. The Herfindahl–Hirschman Index (HHI) and the biggest k-banks Concentration Ratio (CRk), which measure concentration changes over 17 years during the period 1998-2014, are used in this study.FindingsThe study finds that Oman’s Banking Industry is highly concentrated, which should cause concerns over these two requests of mergers or similar requests in the future. In general, the concentration ratio shows decreasing trend. The concentration ratio in the deposit market implies a concentrated market with CR2 and CR3 recording 67 and 85%, respectively, while HHI reached 2,864 points in the 1998. However, in 2014, the concentration ratio had decreased, to CR2 and CR3 recording 52 and 65% respectively, and HHI standing at 2,112 points.Research limitations/implicationsThe researcher suggests future investigation and further research in setting a benchmark index as a guideline for mergers’ requests.Practical implicationsExercising monopoly power, by fewer banks, is very harmful to the economy. Charging higher interest rates on business loans escalates the cost of production of products and services which will cause inflation; therefore, monopoly power will lead to slow growth of the economy.Social implicationsRegulators in Central Bank of Oman (CBO) or in any central bank should be very careful in granting mergers, especially among big banks, because it enables newly bigger banks to exercise monopoly power, thereby harming depositors who will be getting low deposit interest rates and harming borrowers by charging them high loan interest rate.Originality/valueEven though, this study discussed two requests of mergers between banks in Oman; however, it has presented formal approaches to the measurement of market structure in any country. Overall, it provides the policymakers in making the final decisions on mergers between banks in the future which are not limited to these banks or to Oman’s Banking Industry.

New ISE-Based Apparatus for Na+, K+, Cl-, pH and Transepithelial Potential Difference Real-Time Simultaneous Measurements of Ion Transport across Epithelial Cells Monolayer⁻Advantages and Pitfalls.

Cystic Fibrosis (CF) is the most common fatal human genetic disease, which is caused by a defect in an anion channel protein (CFTR) that affects ion and water transport across the epithelium. We devised an apparatus to enable the measurement of concentration changes of sodium, potassium, chloride, pH, and transepithelial potential difference by means of ion-selective electrodes that were placed on both sides of a 16HBE14σ human bronchial epithelial cell line that was grown on a porous support. Using flat miniaturized ISE electrodes allows for reducing the medium volume adjacent to cells to approximately 20 μL and detecting changes in ion concentrations that are caused by transport through the cell layer. In contrast to classic electrochemical measurements, in our experiments neither the calibration of electrodes nor the interpretation of results is simple. The calibration solutions might affect cell physiology, the medium composition might change the direction of actions of the membrane channels and transporters, and water flow that might trigger or cut off the transport pathways accompanies the transport of ions. We found that there is an electroneutral transport of sodium chloride in both directions of the cell monolayer in the isosmotic transepithelial concentration gradient of sodium or chloride ions. The ions and water are transported as an isosmotic solution of 145 mM of NaCl.

The haematological, proinflammatory cytokines and IgG changes during an ovine experimental theileriosis.

Malignant ovine theileriosis is caused by Theileria lestoquardi, which is highly pathogenic in sheep. Theileriosis involves different organs in ruminants. Little is known about the role of proinflammatory cytokines in the pathogenesis of T. lestoquardi infection. The aim of this study was to measure concentration changes of proinflammatory cytokines and immunoglobulin G (IgG) during an ovine experimental theileriosis and correlate it with clinical and haematological parameters. During an experimental study, seven healthy Baluchi sheep (four females and three males) about 6–8 months old were infected with T. lestoquardi by feeding of infected unfed ticks on the sheep’s ears. The infected sheep were clinically examined during the study and blood samples were collected on days 0, 2, 5, 7, 10, 12, 14, 17 and 21. The haematological parameters were analysed by an automatic veterinary haematology cell counter and the inflammatory cytokines interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and IgG were measured by enzyme-linked immunosorbent assay. All infected sheep had temperatures above 40 °C on days 3–4 post infection (PI). The maximum temperature was noted on day 7, and it remained high until day 21. The parasitaemia of T. lestoquardi infection increased from 0.01% (day 7 PI) to 3.3% (day 21 PI). The mean white blood cell (WBC), red blood cell (RBC), lymphocyte, neutrophil and platelet values slightly increased on day 2 PI and decreased by day 17 and day 21 PI. The percentage parasitaemia and fever had a negative correlation with the numbers of WBCs, RBCs, lymphocytes, neutrophils and platelets. The serum concentration of IL-6, TNF-α and IFN-γ cytokines increased and peaked on day 12 and thereafter decreased to levels lower than 0. Out of all tested cytokines, the concentration of IL-6 was significantly higher, as early as day 2 PI. No significant changes were observed for the IgG levels during the course of disease. A significant and strong correlation was observed between IL-6, TNF-α and IFN-γ values and a moderate correlation between IL-6 and the numbers of lymphocytes in the present study. A strong correlation was determined between the percentage parasitaemia and haematological parameters in T. lestoquardi-infected sheep. In addition, preliminary results indicate that the measurement of the serum concentrations of IL-6 in combination with haematological parameters could be considered a good marker to estimate the pathogenicity of T. lestoquardi strain.

Muscle deoxygenation during moderate- and severe-intensity cycling in youth elite-cyclists

Background: Near-infrared spectroscopy (NIRS) is a well-established technique to measure tissue oxygenation and haemodynamics during exercise. While muscle oxygen consumption is derived by measuring concentration changes of oxygenated and deoxygenated haemoglobin and myoglobin (O 2 Hb and HHb), total haemoglobin (tHb = O 2 Hb + HHb) reflect blood volume and perfusion. In particular, the change in HHb is considered a proxy for oxygen extraction at the muscle level during exercise and arterial occlusion, where the rate of reoxygenation has been used as a measure of mitochondrial function (Ryan et al, 2012: Journal of Applied Physiology, 113, 175-183). NIRS-derived signals therefore reflect the dynamic balance between oxygen delivery and utilisation and may be important measures to monitor training induced adaptations of aerobic function in skeletal muscle. However, current literature is scarce regarding reliability measures, especially in young athletes, which needs to be established to interpret changes with confidence. Purpose: To assess the test-retest reliability of HHb-changes during moderate- and severe- intensity cycling, and during arterial occlusion in youth elite-cyclists. Methods: Fifteen cyclist (mean ± SD: age 13.5 ± 1.8 y; stature 163.2 ± 12.2 cm; body mass 51.3 ± 12.4 kg; O 2max 62.1 ± 4.2 mL . min -1. kg -1 ) completed two 6-min rest-to-work transitions (T) from baseline (BL: 60 W) to moderate- (90% of the first ventilatory threshold [VT1]: 120 ± 26 W) and to severe- (50% between VT and maximum power [Delta50]: 204 ± 43 W) intensity cycling. The transitions were interspersed by 8 min BL cycling. After Delta50 cycling, an occlusion was applied on the proximal thigh at a pressure of 300 mmHG until a levelling-off of the HHb signal was observed (3-5 min). The protocol was repeated after a passive rest of 1 h. Changes in HHb were measured on the belly of the right vastus lateralis muscle with a portable continuous-wave NIRS device at a sampling rate of 5 Hz (PortaMon, Artinis). Second-per-second data, were corrected for blood volume changes and normalised to the full functional range measured during the occlusion (0-100%). HHb changes (%) were calculated from BL to the maximum of VT1 (I”BL-VT1) and from BL to the maximum of Delta50 (I”BL-Delta50). In addition, the reoxygenation after occlusion was assessed with the slope of linear regression analysis (% . s -1 ). A typical example of the HHb signal is shown in Figure 1. Absolute and relative reliability was calculated with Bland-Altman statistics ± 95% limits of agreement and the coefficient of variation (CV; %), respectively. Paired t-tests were used for comparisons. Results: The I”BL-VT1 was 20.5 ± 11.7 and 21.6 ± 12.3% during T1 and T2, respectively (p = 0.079). The bias was 1.1 ± 2.3 % (95% LoA: -5.6 – 3.3) and the CV 10.1% (7.3 – 16.4). The I”BL-Delta50 were 58.1 ± 9.6 (T1) and 56.5 ± 9.3% (T2) (p = 0.133) and the bias and CV were 1.6 ± 3.9% (-6.0 – 9.3) and 5.4% (3.9 – 8.6), respectively. The reoxygenation slopes were 7.2 ± 2.0 (T1) and 7.6 ± 2.1 % . s -1 (T2) (p = 0.053) with a bias and CV of 0.4 ± 0.7 % . s -1 (-1.8 – 1.0) and 7.0% (5.1 – 11.2), respectively. Discussion: The present study quantified reliability for NIRS-derived changes in HHb during cycling at moderate and severe intensity as well as for reoxygenation after occlusion. The provided levels of 5.4% for severe-intensity cycling and 7.0% for the reoxygenation slope, are well below the level of 10% considered as acceptable for a measurement, and the level of 10.1% for moderate-intensity cycling is only marginally higher. The reliability data established, provide limits within which training induced adaptations may be interpreted with confidence. Longitudinal studies in young athletes could potentially benefit from these findings since the magnitude of changes in NIRS variables is probably greater than the reported measurement error.

An improved PADDY model including uptake by rice roots to predict pesticide behavior in paddy fields under nursery-box and submerged applications.

We developed an improved version of the PADDY model for predicting pesticide behavior in paddy fields, which includes pesticide uptake by rice roots. We applied the model to nursery-box and submerged pesticide applications. A paddy field was divided into root-zone and inter-plant areas, and paddy soil containing pesticides was vertically separated into three layers. Pesticide behavior was modeled with mass fractions of the pesticides in paddy water and the soil layers immediately after rice transplanting obtained from field experiments, and uptake by rice roots was described using the transpiration stream concentration factor. The improved model successfully simulated measured concentration changes in a paddy field, including rice plants, under nursery-box and submerged applications. The model evaluated the difference in the concentrations of nursery-box-applied pesticides between root-zone and inter-plant soil samples with several key parameters. Our study provides a useful solution for simulating the uptake of pesticides in soil by rice roots.

Investigate the effect of HD-tDCS on the prefrontal cortex using fNIRS for neurorehabilitation

Investigate the effect of HD-tDCS on the prefrontal cortex using fNIRS for neurorehabilitation

Relation Between Asymmetry of Prefrontal Activity and Autonomic Nervous System in Post-stroke Patients with a Disorder of Consciousness.

Early mobilization and rehabilitation of stroke patients can improve functional recovery. However, effects of mobilization on the responses of the autonomic nervous system (ANS) and emotions in post-stroke patients are not yet clear, particularly in patients with disorders of consciousness. We evaluated the effects of standing load on the ANS and emotions of post-stroke patients (n=8, 70.8 ± 11.8years) with a disorder of consciousness by measuring the prefrontal cortex (PFC) activity, which plays important roles in regulation of the ANS and emotions. Employing near infrared spectroscopy (NIRS), we measured concentration changes of oxygenated haemoglobin (oxy-Hb) in the PFC for 10 min at rest. Then, subjects were placed in supine position on a tilt table, and standing loads were given by 30°, 45° and 60° every 5 min. We assessed left-right asymmetry of the PFC activity at rest by calculating the Laterality Index at Rest (LIR; LIR>0 indicates right dominant activity while LIR<0 indicates left dominant activity). We observed fluctuations of oxy-Hb in the PFC at rest, indicating activation of the PFC. Interestingly, 75% (six patients) of the patients exhibited right dominant PFC activation at rest. These patients exhibited an increase of oxy-Hb during standing load; four patients suffered from orthostatic hypotension. Finally, there was a significant positive correlation between LIR before the standing test and oxy-Hb changes during the standing test (r=0.78, p=0.02). These results suggest that the standing load might act on post-stroke patients as a stressor, which caused an increase of PFC activity (i.e., rCBF). NIRS may be useful to assess feasibility to start rehabilitation of post-stroke patients with a disorder of consciousness.

Fast Scan Cyclic Voltammetry with Microdialysis for Quantitative Measurement of Dopamine

Microdialysis methods have been widely used for the quantitative measurement of neurotransmitter concentrations in vivo. Because neurotransmitter efflux happens rapidly, microdialysis has a limit to detect neurochemical changes in the brain in real time. Fast-scan cyclic voltammetry (FSCV) is one of the electroanalytical methods to monitor neurotransmitter efflux such as dopamine, serotonin, adenosine, and ascorbic acid in the brain. Because conventional FSCV analyzes voltammagram differences to detect chemical substances, measuring concentrations of neurotransmitters is desirable. In a previous study we introduced a new method using multi-waveform cyclic voltammetry to reduce voltammogram differences and enhance sensitivity and selectivity. In this study, we demonstrated FSCV with a carbon fiber microelectrode (CFM) adjacent to a microdialysis probe to measure concentration changes during microdialysis. Experiments were performed in agarose gel (0.1%) with a known concentration of dopamine inside, and perfusion of the dialysis probe with Tris-buffered saline (TBS, pH7.4, 5ul/min) decreased the baseline. After stabilization, a series of known concentrations of dopamine (200nM to 1uM) was perfused and concentration changes were monitored by FSCV until the decreased baseline was recovered. These results indicate that the amount of dopamine injected when decrease baseline is fully recovered reflects the concentration of dopamine inside the agarose gel. FSCV combined with microdialysis was also performed in the striatum of a rat, to monitor basal level of dopamine in the extracellular space of the brain.

Interrelationship Between Broadband NIRS Measurements of Cerebral Cytochrome C Oxidase and Systemic Changes Indicates Injury Severity in Neonatal Encephalopathy.

Perinatal hypoxic ischaemic encephalopathy (HIE) is associated with severe neurodevelopmental problems and mortality. There is a clinical need for techniques to provide cotside assessment of the injury extent. This study aims to use non-invasive cerebral broadband near-infrared spectroscopy (NIRS) in combination with systemic physiology to assess the severity of HIE injury. Broadband NIRS is used to measure the changes in haemodynamics, oxygenation and the oxidation state of cytochrome c oxidase (oxCCO). We used canonical correlation analysis (CCA), a multivariate statistical technique, to measure the relationship between cerebral broadband NIRS measurements and systemic physiology. A strong relationship between the metabolic marker, oxCCO, and systemic changes indicated severe brain injury; if more than 60 % of the oxCCO signal could be explained by the systemic variations, then the neurodevelopmental outcome was poor. This boundary has high sensitivity and specificity (100 and 83 %, respectively). Broadband NIRS measured concentration changes of the oxidation state of cytochrome c oxidase has the potential to become a useful cotside tool for assessment of injury severity following hypoxic ischaemic brain injury.

Oxygen metabolism and pH in coastal ecosystems: Eddy Covariance Hydrogen ion and Oxygen Exchange System (ECHOES)

An aquatic eddy covariance (EC) system was developed to measure the exchange of oxygen (O2) and hydrogen ions (H+) across the sediment-water interface. The system uses O2 optodes and a newly developed micro-flow cell H+ ion selective field effect transistor; these sensors displayed sufficient precision and rapid enough response times to measure concentration changes associated with turbulent exchange. Discrete samples of total alkalinity and dissolved inorganic carbon were used to determine the background carbonate chemistry of the water column and relate the O2 and H+ fluxes to benthic processes. The ECHOES system was deployed in a eutrophic estuary (Waquoit Bay), and revealed that the benthos was a sink for acidity during the day and a source of acidity during the night, with H+ and O2 fluxes of ± 0.0001 and ± 10 mmol m−2 h−1, respectively. H+ and O2 fluxes were also determined using benthic flux chambers, for comparison with the EC rates. Chamber fluxes determined in 0.25 h intervals co-varied with EC fluxes but were ∼ 4 times lower in magnitude. This difference was likely due to suppressed pore-water advection in the chambers and changes in the chemistry of the enclosed chamber overlying water. The individual H+ and O2 fluxes were highly correlated in each dataset (EC and chambers), and both methods yielded H+ fluxes that could not be explained by O2 metabolism alone. The ECHOES system provides a new tool for determining the influence of benthic biogeochemical cycling on coastal ocean acidification and carbon cycling.