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A method for the determination of selected aromatic amino acid biomarkers of oxidative stress using microchip electrophoresis with electrochemical detection is described. The separation of the major reaction products of phenylalanine and tyrosine with reactive nitrogen and oxygen species was accomplished using ligand exchange micellar electrokinetic chromatography with a PDMS/glass hybrid chip. Electrochemical detection was achieved using a pyrolyzed photoresist film working electrode. The system was evaluated for the analysis of the products of the Fenton reaction with tyrosine and phenylalanine, and the reaction of peroxynitrite with tyrosine. [ABSTRACT FROM AUTHOR]

Microdialysis is a powerful sampling technique that enables monitoring of dynamic processes in vitro and in vivo . The combination of microdialysis with chromatographic or electrophoretic methods with selective detection yields a “separation-based sensor” capable of monitoring multiple analytes in near real time. For monitoring biological events, analysis of microdialysis samples often requires techniques that are fast (<1 min), have low volume requirements (nL–pL), and, ideally, can be employed on-line. Microchip electrophoresis fulfills these requirements and also permits the possibility of integrating sample preparation and manipulation with detection strategies directly on-chip. Microdialysis coupled to microchip electrophoresis has been employed for monitoring biological events in vivo and in vitro . This review discusses technical considerations for coupling microdialysis sampling and microchip electrophoresis, including various interface designs, and current applications in the field. [ABSTRACT FROM AUTHOR]

Abstract: Microdialysis (MD) is a sampling technique that can be employed to monitor biological events both in vivo and in vitro. When it is coupled to an analytical system, microdialysis can provide near real-time information on the time-dependent concentration changes of analytes in the extracellular space or other aqueous environments. Online systems for the analysis of microdialysis samples enable fast, selective and sensitive analysis while preserving the temporal information. Analytical methods employed for online analysis include liquid chromatography (LC), capillary (CE) and microchip electrophoresis and flow-through biosensor devices. This review article provides an overview of microdialysis sampling and online analysis systems with emphasis on in vivo analysis. Factors that affect the frequency of analysis and, hence, the temporal resolution of these systems are also discussed. [Copyright &y& Elsevier]

The fabrication and evaluation of a palladium decoupler and working electrode for microchip capillary electrophoresis (CE) with electrochemical detection is described. The use of the Pd decoupler allows the working electrode to be placed directly in the separation channel and eliminates the band-broadening characteristic of the end-channel configuration. The method used for fabrication of the decoupler and working electrode was based on thin-layer deposition of titanium followed by palladium onto a glass substrate. When employed as the cathode in CE, palladium absorbs the hydrogen gas that is generated by the hydrolysis of water. The effect of the decoupler size on the ability to remove hydrogen was evaluated with regard to reproducibility and longevity. Using boric acid and TES buffer systems, 500 μm was determined to be the optimum decoupler size, with effective voltage isolation lasting for ∼6 h at a constant field strength of 600 V/cm. The effect of distance between the decoupler and working electrode on noise and resolution for the separation of dopamine and epinephrine was also investigated. It was found that 250 μm was the optimum spacing between the decoupler and working electrode. At this spacing, laser-induced fluorescence detection at various points around the decoupler established that the band broadening due to pressure-induced flow that occurs after the decoupler did not significantly affect the separation efficiency of fluorescein. Limits of detection, sensitivity, and linearity for dopamine (500 nM, 3.5 pA/μM, r² = 0.9996) and epinephrine (2.1 μM, 2.6 pA/μM, r² = 0.9996) were obtained using the palladium decoupler in combination with a Pd working electrode. [ABSTRACT FROM AUTHOR]

The amine derivatization reagent p-nitrophenol-2,5-dihydroxyphenylacetate bis-tetrahydropyranyl ether (NDTE) was used in conjunction with capillary electrophoresis (CE) and electrochemical detection (EC) for the pre-separation derivatization of primary amine analytes present in aqueous solution. Glycine, several dipeptides and angiotensin II were used as model analytes. A miniaturized EC detection cell was designed and fabricated, which featured a fractured-joint field decoupler with a fixed end-column carbon fiber electrode. When a series of glycine and angiotensin II calibration solutions were derivatized with NDTE followed by CE–EC determination, linear calibration plots resulted with pre-derivatization concentration limits of detection of 500 nM (106 attomoles on-column) and 6 μM (1.275 femtomoles on-column), respectively. [Copyright &y& Elsevier]

Focuses on literature and references related to applications of the separation and analysis of peptides and proteins between 1997 and 1998. Reversed-phase liquid chromatography; Salt-promoted adsorption chromatography; Ultrafiltration.

Describes two reagents for the chemical derivatization of primary and/or secondary amines to form an electrochemically active product. Reagent design; Ease of oxidation while maintaining stability in acid media; Miniaturization of sample size requirements.

Discusses the development of a wire-wire on-capillary dual electrode that is suited for bromine-based postcolumn reaction. Oxidation of bromide to bromine; Reactivity of bromine with a variety of compounds; Linear response for cysteine; Limits of detection; Elements to be considered in developing reaction detection method for capillary electrophoresis.

Provides information on a study on dual-electrode detector of disulfide and thiols through capillary electrophoresis. Information on capillary electrophoresis with electrochemical detection (CEEC); Evaluation of detector configuration using single-electrode detection; Results and discussion.

Describes an on-capillary electrochemical detector for capillary electrophoresis. Use of the detector for off-column detection of catecholamines and end-column detection of carbohydrates; Schemes employed in capillary electrophoresis/electrochemistry; Separation of catecholamines using on-capillary detection.

Describes a fabrication method for a Nafion joint for capillary electrophoresis with on-column electrochemical detection (CEEC). Effect of electrode position on detection parameters; Comparison of casting methods; Effect of joint length on detector noise; Effect of joint length on peak shape; On-line hydrogen ion concentration adjustment.

Describes the development of a membrane-based on-column mixer for capillary electrophoresis. Background of the study; Information about the experiment; Results and discussion of the study.

Describes an on-line coupling of microdialysis sampling to capillary electrophoretic (EC) analysis. Use of microcolumn separation to overcome small volume limitation; On-line interface precision; High-speed micellar electrokinetic chromatography (MEKC) separation; Determination of SR 4233 pharmacokinetics.

Describes the design and application of chemically modified microelectrodes for capillary electrophoresis. Immobilization of different types of modifiers into a carbon paste matrix; Catalysis of oxidation of analytes; Increase in selectivity in urine analysis.

Carnosine is an endogenous dipeptide composed of β-alanine and L-histidine, possessing a multimodal pharmacodynamic profile that includes anti-inflammatory and anti-oxidant activities. Carnosine has also shown its ability to modulate cell proliferation, cell cycle arrest, apoptosis, and even glycolytic energy metabolism, all processes playing a key role in the context of cancer. Cancer is one of the most dreaded diseases of the 20th and 21st centuries. Among the different types of cancer, breast cancer represents the most common non-skin cancer among women, accounting for an estimated 15% of all cancer-related deaths in women. The main aim of the present review was to provide an overview of studies on the anti-cancer activity of carnosine, and in particular its activity against breast cancer. We also highlighted the possible advantages and limitations involved in the use of this dipeptide. The first part of the review entailed a brief description of carnosine's biological activities and the pathophysiology of cancer, with a focus on breast cancer. The second part of the review described the anti-tumoral activity of carnosine, for which numerous studies have been carried out, especially at the preclinical level, showing promising results. However, only a few studies have investigated the therapeutic potential of this dipeptide for breast cancer prevention or treatment. In this context, carnosine has shown to be able to decrease the size of cancer cells and their viability. It also reduces the levels of vascular endothelial growth factor (VEGF), cyclin D1, NAD+, and ATP, as well as cytochrome c oxidase activity in vitro. When tested in mice with induced breast cancer, carnosine proved to be non-toxic to healthy cells and exhibited chemopreventive activity by reducing tumor growth. Some evidence has also been reported at the clinical level. A randomized phase III prospective placebo-controlled trial showed the ability of Zn–carnosine to prevent dysphagia in breast cancer patients undergoing adjuvant radiotherapy. Despite this evidence, more preclinical and clinical studies are needed to better understand carnosine's anti-tumoral activity, especially in the context of breast cancer. [ABSTRACT FROM AUTHOR]

Many separation methods have been developed for biomedical analysis, including chromatographic ( e.g. high performance liquid chromatography (HPLC) and gas chromatography (GC)) and electrophoretic methods ( e.g. gel electrophoresis and capillary electrophoresis (CE)). Among these techniques, CE provides advantages in terms of high separation efficiency, simplicity, low sample and solvent volume consumption, short analysis time and applicability to a wide range of biomedically important substances. Microchip electrophoresis (ME) is a miniaturized platform of CE and is now considered as a simpler and more convenient alternative, which has demonstrated potential in analytical chemistry. High-throughput, cost-effective and portable analysis systems can be developed using ME. The current review describes different separation modes and detectors that have been employed in ME to analyze various classes of biomedical analytes ( e.g. pharmaceuticals and related substances, nucleic acids, amino acids, peptides, proteins, antibodies and antigens, carbohydrates, cells, cell components and lysates). Recent applications (during 2010–2014) in these areas are presented in tables and some significant findings are highlighted. [ABSTRACT FROM AUTHOR]

Describes the indirect measurement of nitric oxide production by monitoring nitrate and nitrite using microchip capillary electrophoresis with electrochemical detection. Conversion of nitrate to nitrite; Quantification of the amount nitrite; Determination of small inorganic anions.

The transport of substance P (SP) was investigated using the bovine brain microvessel endothelial cell culture model of the blood-brain barrier (BBB). The samples were derivatized precolumn with naphthalene dialdehyde, then analyzed by cyclodextrin-modified micellar electrokinetic chromatography with laser-induced fluorescence detection. SP crossed the BBB in both the apical-to-basolateral and basolateral-to-apical directions through an active transport mechanism. The transport of SP from the apical side was demonstrated to be via transcytosis. The N-terminal (SP1–4) and C-terminal (SP3–11) fragments were also found to permeate the BBB from the apical side. [Copyright &y& Elsevier]

Microchip electrophoresis with amperometric detection (ME-EC) is a useful tool for the determination of redox active compounds in complex biological samples. In this review, a brief background on the principles of ME-EC is provided, including substrate types, electrode materials, and electrode configurations. Several different detection approaches are described, including dual-channel systems for dual-electrode detection and electrochemistry coupled with fluorescence and chemiluminescence. The application of ME-EC to the determination of catecholamines, adenosine and its metabolites, and reactive nitrogen and oxygen species in microdialysis samples and cell lysates is also detailed. Lastly, approaches for coupling of ME-EC with microdialysis sampling to create separation-based sensors that can be used for near real-time monitoring of drug metabolism and neurotransmitters in freely roaming animals are provided. [ABSTRACT FROM AUTHOR]

The development of a separation-based sensor for catecholamines based on microdialysis (MD) coupled to microchip electrophoresis (ME) with electrochemical (EC) detection is described. The device consists of a pyrolyzed photoresist film working electrode and a poly(dimethylsiloxane) microchip with a flow-gated sample injection interface. The chip was partially reversibly sealed to the glass substrate by selectively exposing only the top section of the chip to plasma. This partially reversible chip/electrode integration process not only allows the reuse of the working electrode but also greatly enhanced the reproducibility of electrode alignment with the separation channel. The developed MD–ME–EC system was then tested using L -DOPA, 3-O-MD, HVA, DOPAC, and dopamine standards, which were separated in less than 100 seconds using a background electrolyte consisting of 15 mM sodium phosphate (pH 7.4), 15 mM sodium dodecyl sulfate, and 2.5 mM boric acid. A potential of +1.0 V vs. Ag/AgCl was used for amperometric detection of the analytes. The device was evaluated for on-line monitoring of the conversion of L -DOPA to dopamine in vitro and for monitoring dopamine release in an anesthetized rat in vivo following high K+ stimulation. The system was able to detect stimulated dopamine release in vivo but not endogenous levels of dopamine. [ABSTRACT FROM AUTHOR]

Microchip electrophoresis coupled with amperometric detection is more popular than voltammetric detection due to the lower limits of detection that can be achieved. However, voltammetry provides additional information about the redox properties of the analyte that can be used for peak identification. In this paper, two dual electrode configurations for microchip electrophoresis are described and evaluated for obtaining voltammetric information using amperometry. The dual-series electrode configuration was first evaluated to generate current ratios in a single run by applying two different potentials to the working electrodes placed perpendicular to the separation channel. However, it was found that it is difficult to obtain realistic current ratios with this configuration, primarily due to the relative placement of electrodes with respect to the channel end of the simple-t microchip. Correction factors were needed to obtain current ratios similar to those that would be obtained for sequential injections at two different potentials using a single electrode. A second approach using a dual-channel chip with two parallel electrodes was then developed and evaluated for obtaining voltammetric identification. The newly developed microchip permitted the injection of same amount of sample into two unique separation channels, each with an electrode at a different detection potential. Migration times and current ratios for several biologically important molecules and potential interferences including nitrite, tyrosine, hydrogen peroxide, and azide were obtained and compared to the responses obtained for analytes found in macrophage cell lysates. [ABSTRACT FROM AUTHOR]

The development of an on-animal separation-based sensor that can be employed for monitoring drug metabolism in a freely roaming sheep is described. The system consists of microdialysis sampling coupled to microchip electrophoresis with electrochemical detection (MD-ME-EC). Separations were accomplished using an all-glass chip with integrated platinum working and reference electrodes. Discrete samples from the microdialysis flow were introduced into the electrophoresis chip using a flow-gated injection approach. Electrochemical detection was accomplished in-channel using a two-electrode isolated potentiostat. Nitrite was separated by microchip electrophoresis using reverse polarity and a run buffer consisting of 50 mM phosphate at pH 7.4. The entire system was under telemetry control. The system was first tested with rats to monitor the production of nitrite following perfusion of nitroglycerin into the subdermal tissue using a linear probe. The data acquired using the on-line MD-ME-EC system were compared to those obtained by off-line analysis using liquid chromatography with electrochemical detection (LC-EC), using a second microdialysis probe implanted parallel to the first probe in the same animal. The MD-ME-EC device was then used on-animal to monitor the subdermal metabolism of nitroglycerin in sheep. The ultimate goal is to use this device to simultaneously monitor drug metabolism and behavior in a freely roaming animal. [ABSTRACT FROM AUTHOR]

The overproduction of nitric oxide (NO) in cells results in nitrosative stress due to the generation of highly reactive species such as peroxynitrite and N2O3. These species disrupt the cellular redox processes through the oxidation, nitration, and nitrosylation of important biomolecules. Microchip electrophoresis (ME) is a fast separation method that can be used to profile cellular nitrosative stress through the separation of NO and nitrite from other redox-active intracellular components such as cellular antioxidants. This paper describes a ME method with electrochemical detection (ME-EC) for the separation of intracellular nitrosative stress markers in macrophage cells. The separation of nitrite, azide (interference), iodide (internal standard), tyrosine, glutathione, and hydrogen peroxide (neutral marker) was achieved in under 40 s using a run buffer consisting of 7.5 to 10 mM NaCl, 10 mM boric acid, and 2 mM TTAC at pH 10.3 to 10.7. Initially, NO production was monitored by the detection of nitrite (NO2−) in cell lysates. There was a 2.5- to 4-fold increase in NO2− production in lipopolysaccharide (LPS)-stimulated cells. The concentration of NO2− inside a single unstimulated macrophage cell was estimated to be 1.41 mM using the method of standard additions. ME-EC was then used for the direct detection of NO and glutathione in stimulated and native macrophage cell lysates. NO was identified in these studies based on its migration time and rapid degradation kinetics. The intracellular levels of glutathione in native and stimulated macrophages were also compared, and no significant difference was observed between the two conditions. [ABSTRACT FROM AUTHOR]

A considerable amount of attention has been focused on the analysis of single cells in an effort to better understand cell heterogeneity in cancer and neurodegenerative diseases. Although microfluidic devices have several advantages for single cell analysis, few papers have actually demonstrated the ability of these devices to monitor chemical changes in perturbed biological systems. In this paper, a new microfluidic channel manifold is described that integrates cell transport, lysis, injection, electrophoretic separation, and fluorescence detection into a single device, making it possible to analyze individual cells at a rate of 10 cells/min in an automated fashion. The system was employed to measure nitric oxide (NO) production in single T-lymphocytes (Jurkat cells) using a fluorescent marker, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA). The cells were also labeled with 6-carboxyfluorescein diacetate (6-CFDA) as an internal standard. The NO production by control cells was compared to that of cells stimulated using lipopolysaccharide (LPS), which is known to cause the expression of inducible nitric oxide synthase (iNOS) in immune-type cells. Statistical analysis of the resulting electropherograms from a population of cells indicated a 2-fold increase in NO production in the induced cells. These results compare nicely to a recently published bulk cell analysis of NO. [ABSTRACT FROM AUTHOR]

Abstract: Dynorphin A 1–17 (Dyn A 1–17) is an endogenous neuropeptide known to act at the kappa opioid receptor; it has been implicated in a number of neurological disorders, including neuropathic pain, stress, depression, and Alzheimer''s and Parkinson''s diseases. The investigation of Dyn A 1–17 metabolism at the blood–brain barrier (BBB) is important since the metabolites exhibit unique biological functions compared to the parent compound. In this work, Dyn A 1–6 is identified as a metabolite of Dyn A 1–17 in the presence of bovine brain microvessel endhothelial cells (BBMECs), using LC–MS/MS. The transport of Dyn A 1–6 at the BBB was examined using this in vitro cell culture model of the BBB. Furthermore, the permeation of the BBB by the low molecular weight permeability marker fluorescein was characterized in the presence and absences of Dyn A 1–6. [Copyright &y& Elsevier]

Abstract: The feasibility of using an osmotic pump in place of a syringe pump for microdialysis sampling in rat brain was investigated. The use of an osmotic pump permits the rat to be free from the constraints of the standard tethered system. The in vitro flow rates of a microdialysis syringe pump (set at 10.80μl/h) and the osmotic pump (pump specifications were 11.35μl/h) with no probe attached were compared, yielding results of 10.87μl/h±1.7% and 10.95μl/h±8.0%, respectively. The average of four flow rate experiments in vivo yielded R.S.D.s less than 10% and an average flow rate of 11.1μl/h. Following the flow rate studies, in vivo sampling of neurotransmitters was accomplished with the osmotic pump coupled to a microdialysis probe implanted in the brain. Finally, after determination of basal levels of 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindole-3-acetic acid (5-HIAA) in the rats, the rats were dosed with benserazide followed by l-3,4-dihydroxyphenylalanine (l-DOPA). The results from the dosing study showed at least a 10-fold increase in compounds in the l-DOPA metabolic pathway (DOPAC and HVA) and a slight or no increase in 5-HIAA (serotonin metabolic pathway.) These results indicate that the osmotic pump is a viable alternative to the syringe pump for use in microdialysis sampling. [Copyright &y& Elsevier]

Abstract: Substance P (SP) has been associated with pain and depression as well as neurodegenerative diseases. Many of these diverse actions of SP can potentially be attributed to SP metabolites generated at the blood–brain barrier (BBB). In this study, the metabolism of SP was investigated using an in vitro model of the BBB and LC–MS/MS. Substance P metabolism was found to be non-saturable in the concentration range of 100nM to 10μM, with approximately 70% of the peptide remaining intact after 5h. The major metabolites of SP were identified by MS as 3-11 and 5-11. Two previously unreported metabolites, 5-11 and 6-11, were also found in our studies. Several additional minor SP metabolites, including 1-9 and 2-11, were also identified. A profile of the SP metabolites generated by the BBB over time was obtained. The results from the present study provide a better understanding of the role of the blood–brain barrier in the pharmacology of SP. [Copyright &y& Elsevier]

Abstract: The integration of rapid on-chip sample derivatization employing naphthalene 2,3-dicarboxaldehyde and 2-mercaptoethanol (NDA/2ME) with an easily assembled microdialysis/microchip electrophoresis device was carried out. The microchip device consisted of a glass layer with etched microfluidic channels that was sealed with a layer of poly(dimethylsiloxane) (PDMS) via plasma oxidation. This simple sealing procedure alleviated the need for glass thermal bonding and allowed the device to be re-sealed in the event of blockages within the channels. The device was used for analysis of a mixture of amino acids and peptides derivatized on-chip with NDA/2ME for laser-induced fluorescence (LIF) detection. A 0.6mM NDA/1.2mM 2ME mixture was simply added into the buffer reservoir for dynamic on-column derivatization of sample mixtures introduced at a flow rate of 1.0μl/min. Using this scheme, sample injection plugs were derivatized and separated simultaneously. Injections of ca. 12fmol of 5mM amino acid and peptide samples were conducted using the system. Finally, a three-component mixture of Arg, Gly–Pro, and Asp was sampled from a vial using microdialysis, derivatized, separated and detected with the system. The ultimate goal of this effort is the creation of a micro-total analysis system for high-temporal resolution monitoring of primary amines in biological systems. [Copyright &y& Elsevier]

Abstract: A method for the separation and direct detection of peroxynitrite (ONOO−) and two of its degradation products, nitrite (NO2 −) and nitrate (NO3 −), using capillary electrophoresis with ultraviolet detection is described. The separation parameters were optimized and included electrokinetic injection, a run buffer consisting of 25mM K2HPO4 7.5mM DTAB, pH 12, and a field strength of −323V/cm. A diode array UV detector was employed in these studies as it allowed the determination of all three species simultaneously. Nitrate and nitrite provided the maximum response at 214nm while peroxynitrite generated the best response at 302nm. All three species could be detected at 214nm, while simultaneous detection at 214 and 302nm positively identified each peak. [Copyright &y& Elsevier]

This work describes the fabrication and evaluation of a poly(dimethyl)siloxane (PDMS)-based device that enables the discrete injection of a sample plug from a continuous-flow stream into a microchannel for subsequent analysis by electrophoresis. Devices were fabricated by aligning valving and flow channel layers followed by plasma sealing the combined layers onto a glass plate that contained fittings for the introduction of liquid sample and nitrogen gas. The design incorporates a reduced-volume pneumatic valve that actuates (on the order of hundreds of milliseconds) to allow analyte from a continuously flowing sampling channel to be injected into a separation channel for electrophoresis. The injector design was optimized to include a pushback channel to flush away stagnant sample associated with the injector dead volume. The effect of the valve actuation time, the pushback voltage, and the sampling stream flow rate on the performance of the device was characterized. Using the optimized design and an injection frequency of 0.64 Hz showed that the injection process is reproducible (RSD of 1.77%, n = 15). Concentration change experiments using fluorescein as the analyte showed that the device could achieve a lag time as small as 14 s. Finally, to demonstrate the potential uses of this device, the microchip was coupled to a microdialysis probe to monitor a concentration change and sample a fluorescein dye mixture. [ABSTRACT FROM AUTHOR]

Microdialysis sampling is a technique that has been used for in vivo and in vitro monitoring of compounds of pharmaceutical, biomedical, and environmental interest. The coupling of a commercially available microdialysis probe to a microchip-based capillary electrophoresis (CE) system is described. A continuously flowing dialysate stream from a microdialysis probe was introduced into the microchip, and discrete injections were achieved using a valveless gating approach. The effect of the applied voltage and microdialysis flow rate on device performance was investigated. It was found that the peak area varied linearly with the applied voltage. Higher voltages led to lower peak response but faster separations. Perfusion flow rates of 0.8 and 1.0 μL/min were found to provide optimal performance. The on-line microdialysis/microchip CE system was used to monitor the hydrolysis of fluorescein mono-β-n-galactopyranoside (FMG) by fl-D-galactosidase. A decrease of the FMG substrate with an increase in the fluorescein product was observed. The temporal resolution of the device, which is dependent on the CE separadon time, was 30s. To the best of our knowledge, this is the first reported coupling of a microdialysis sampling probe to a microchip capillary electrophoresis device. [ABSTRACT FROM AUTHOR]

A comparative study of electrophoretic separations of fluorescently labeled peptides and amino acids on poly(dimethylsiloxane) (PDMS) and Pyrex microchips is presented. The separation parameters for each microchip substrate were compared, including electroosmotic flow, plate numbers, resolution, and limits of detection. The effect of buffer composition on the separation was also investigated. Acceptable separations were obtained for most peptides with both substrates; however, PDMS chips exhibited much lower separation efficiencies and longer analysis times. [Copyright &y& Elsevier]

Massed training in the conditional discrimination task, the fixed ratio discrimination (FRD) task led to elevated extracellular dopamine (DA) concentrations in the neonatal 6-hydroxydopamine (6-OHDA)-treated rat, a model of Lesch–Nyhan disease (LND). Rats neonatally treated with 6-OHDA or its vehicle were, as adults, implanted with microdialysis probes and assessed for basal pretraining concentrations of DA and its major metabolites. Subsequently, microdialysis samples were collected each day following three separate FRD training periods (trained group) or three separate periods of noncontingent food presentations (untrained group). The present study found that there were significant increases in extracellular DA in the caudate–putamen from basal pretraining concentrations in the repeated sample collections of trained 6-OHDA-lesioned animals but not in the samples of untrained 6-OHDA-lesioned animals. Consistent with previous studies [Brain Res. 508 (1990) 30.], there was an increase in the extracellular concentrations as compared to tissue concentrations of DA and 3,4-dihydroxyphenylacetic acid (DOPAC). Similar to our previous studies with long-term FRD training [Pharmacol. Biochem. Behav. 51 (1995) 861; Brain Res. 713 (1996) 246.], there was also an indication of an increase in cortical and striatal tissue concentration of DA in the trained 6-OHDA-lesioned animals as compared to the untrained 6-OHDA-lesioned animals. The elevations in striatal DA concentrations following operant performance in the present study illustrate how operant procedures of the behavior therapy used with individuals with LND and other mental retardation syndromes may interact with the modulation of dopaminergic function by the pharmaceutical application of DA antagonists to suppress aberrant behaviors. [Copyright &y& Elsevier]

Describes the electrode configuration for microchip capillary electrophoresis (CE) with electrochemical (EC) detection. Utilization of isolated potentiostat; Advantages of integrating EC detection with microchip CE; Construction of decoupler.

Carbon-based nanomaterials are nowadays attracting lots of attention, in particular in the biomedical field, where they find a wide spectrum of applications, including, just to name a few, the drug delivery to specific tumor cells and the improvement of non-invasive imaging methods. Nanoparticles inhaled during breathing accumulate in the lung alveoli, where they interact and are covered with lung surfactants. We recently demonstrated that an apparently non-toxic concentration of engineered carbon nanodiamonds (ECNs) is able to induce oxidative/nitrosative stress, imbalance of energy metabolism, and mitochondrial dysfunction in microglial and alveolar basal epithelial cells. Therefore, the complete understanding of their "real" biosafety, along with their possible combination with other molecules mimicking the in vivo milieu, possibly allowing the modulation of their side effects becomes of utmost importance. Based on the above, the focus of the present work was to investigate whether the cellular alterations induced by an apparently non-toxic concentration of ECNs could be counteracted by their incorporation into a synthetic lung surfactant (DPPC:POPG in 7:3 molar ratio). By using two different cell lines (alveolar (A549) and microglial (BV-2)), we were able to show that the presence of lung surfactant decreased the production of ECNs-induced nitric oxide, total reactive oxygen species, and malondialdehyde, as well as counteracted reduced glutathione depletion (A549 cells only), ameliorated cell energy status (ATP and total pool of nicotinic coenzymes), and improved mitochondrial phosphorylating capacity. Overall, our results on alveolar basal epithelial and microglial cell lines clearly depict the benefits coming from the incorporation of carbon nanoparticles into a lung surfactant (mimicking its in vivo lipid composition), creating the basis for the investigation of this combination in vivo. [ABSTRACT FROM AUTHOR]

Carnosine is a natural endogenous dipeptide widely distributed in mammalian tissues, existing at particularly high concentrations in the muscles and brain and possesses well-characterized antioxidant and anti-inflammatory activities. In an in vitro model of macrophage activation, induced by lipopolysaccharide + interferon-gamma (LPS + IFN-γ), we here report the ability of carnosine to modulate pro-oxidant and pro-inflammatory activities of macrophages, representing the primary cell type that is activated as a part of the immune response. An ample set of parameters aimed to evaluate cytotoxicity (MTT assay), energy metabolism (HPLC), gene expressions (high-throughput real-time PCR (qRT-PCR)), protein expressions (western blot) and nitric oxide production (qRT-PCR and HPLC), was used to assess the effects of carnosine on activated macrophages challenged with a non cytotoxic LPS (100 ng/mL) + IFN-γ (600 U/mL) concentration. In our experimental model, main carnosine beneficial effects were: (1) the modulation of nitric oxide production and metabolism; (2) the amelioration of the macrophage energy state; (3) the decrease of the expressions of pro-oxidant enzymes (Nox-2, Cox-2) and of the lipid peroxidation product malondialdehyde; (4) the restoration and/or increase of the expressions of antioxidant enzymes (Gpx1, SOD-2 and Cat); (5) the increase of the transforming growth factor-β1 (TGF-β1) and the down-regulation of the expressions of interleukins 1β and 6 (IL-1β and IL-6) and 6) the increase of the expressions of Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase-1 (HO-1). According to these results carnosine is worth being tested in the treatment of diseases characterized by elevated levels of oxidative stress and inflammation (atherosclerosis, cancer, depression, metabolic syndrome, and neurodegenerative diseases). [ABSTRACT FROM AUTHOR]

• An animal model for locally induced epilepsy was developed. • Microdialysis sampling was used to monitor neurochemical changes. Unique attenuation of glutamate release was observed. Potentially responsible pathways were further investigated. The objective of this study was to develop an in vivo model for locally induced epilepsy. Epilepsy is a prominent neurological disorder that affects millions of people worldwide. Patients may experience either global seizures, affecting the entire brain, or focal seizures, affecting only one brain region. The majority of epileptic patients experience focal seizures but they go undiagnosed because such seizures can be difficult to detect. To better understand the effects of focal epilepsy on the neurochemistry of a brain region with high seizure diathesis, an animal model for locally induced seizures in the hippocampus was developed. In this model, two seizure events were chemically induced by administering the epileptogenic agent, 3-mercaptopropionic acid (3-MPA), to the hippocampus to disturb the balance between excitatory and inhibitory neurotransmitters in the brain. Microdialysis was used for local delivery of 3-MPA as well as for collection of dialysate for neurochemical analyses. Two periods of seizures separated by varying inter-seizure recovery times were employed, and changes in the release of the excitatory transmitter, glutamate, were measured. Significant differences in glutamate release were observed between the first and second seizure episodes. Diminished glutamate biosynthesis, enhanced glutamate re-uptake, and/or neuronal death were considered possible causes of the attenuated glutamate release during the second seizure episode. Biochemical measurements were indicative that a combination of these factors led to the attenuation in glutamate release. [ABSTRACT FROM AUTHOR]

Carnosine (β-alanyl-L-histidine), a dipeptide, is an endogenous antioxidant widely distributed in excitable tissues like muscles and the brain. Carnosine is involved in cellular defense mechanisms against oxidative stress, including the inhibition of amyloid-beta (Aβ) aggregation and the scavenging of reactive species. Microglia play a central role in the pathogenesis of Alzheimer's disease, promoting neuroinflammation through the secretion of inflammatory mediators and free radicals. However, the effects of carnosine on microglial cells and neuroinflammation are not well understood. In the present work, carnosine was tested for its ability to protect BV-2 microglial cells against oligomeric Aβ1-42-induced oxidative stress and inflammation. Carnosine prevented cell death in BV-2 cells challenged with Aβ oligomers through multiple mechanisms. Specifically, carnosine lowered the oxidative stress by decreasing NO and O2−• intracellular levels as well as the expression of iNOS and Nox enzymes. Carnosine also decreased the secretion of pro-inflammatory cytokines such as IL-1β, simultaneously rescuing IL-10 levels and increasing the expression and the release of TGF-β1. Carnosine also prevented Aβ-induced neurodegeneration in mixed neuronal cultures challenged with Aβ oligomers, and these neuroprotective effects were completely abolished by SB431542, a selective inhibitor of the type-1 TGF-β receptor. Our data suggest a multimodal mechanism of action of carnosine underlying its protective effects on microglial cells against Aβ toxicity with a key role of TGF-β1 in mediating these protective effects. [ABSTRACT FROM AUTHOR]

Human amylin is a 37-residue peptide hormone (hA1-37) secreted by β-cells of the pancreas and, along with insulin, is directly associated with type 2 diabetes mellitus (T2DM). Amyloid deposits within the islets of the pancreas represent a hallmark of T2DM. Additionally, amylin aggregates have been found in blood vessels and/or brain of patients with Alzheimer's disease, alone or co-deposited with β-amyloid. The purpose of this study was to investigate the neuroprotective potential of human amylin in the context of endothelial-neuronal "cross-talk". We initially performed dose-response experiments to examine cellular toxicity (quantified by the [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] MTT assay) of different hA17–29 concentrations in endothelial cells (RBE4). In the culture medium of these cells, we also measured heat shock protein B5 (HspB5) levels by ELISA, finding that even a sub-toxic concentration of hA17–29 (3 µM) produced an increase of HspB5. Using a cell medium of untreated and RBE4 challenged for 48 h with a sub-toxic concentration of hA17–29, we determined the potential beneficial effect of their addition to the medium of neuroblastoma SH-SY5Y cells. These cells were subsequently incubated for 48 h with a toxic concentration of hA17–29 (20 µM). We found a complete inhibition of hA17–29 toxicity, potentially related to the presence in the conditioned medium not only of HspB5, but also of vascular endothelial growth factor (VEGF). Pre-treating SH-SY5Y cells with the anti-Flk1 antibody, blocking the VEGF receptor 2 (VEGFR2), significantly decreased the protective effects of the conditioned RBE4 medium. These data, obtained by indirectly measuring VEGF activity, were strongly corroborated by the direct measurement of VEGF levels in conditioned RBE4 media as detected by ELISA. Altogether, these findings highlighted a novel role of sub-toxic concentrations of human amylin in promoting the secretion of proteic factors by endothelial cells (HspB5 and VEGF) that support the survival and proliferation of neuron-like cells. [ABSTRACT FROM AUTHOR]