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In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based biosensor for the detection of ascorbic acid (AA), O2 and glucose in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC), and sent to a personal computer by means of a miniaturized AM transmitter. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. The in-vivo results confirmed previously published observations on striatal AA, oxygen and glucose dynamics recorded in tethered rats. This approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs on brain neurochemical systems

We have previously shown that manganese enhances L‐dihydroxyphenylanine (L‐DOPA) toxicity to PC12 cells in vitro. The supposed mechanism of manganese enhancing effect [an increase in L‐DOPA and dopamine (DA) auto‐oxidation] was studied using microdialysis in the striatum of freely moving rats. Systemic L‐DOPA [25 mg kg−1 intraperitoneally (i.p.) twice in a 12 h interval] significantly increased baseline dialysate concentrations of L‐DOPA, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and uric acid, compared to controls. Conversely, DA and ascorbic acid concentrations were significantly decreased. A L‐DOPA oxidation product, presumptively identified as L‐DOPA semiquinone, was detected in the dialysate. The L‐DOPA semiquinone was detected also following intrastriatal infusion of L‐DOPA. In rats given L‐DOPA i.p., intrastriatal infusion of N‐acetylcysteine (NAC) significantly increased DA and L‐DOPA dialysate concentrations and lowered those of L‐DOPA semiquinone; in addition, NAC decreased DOPAC+HVA and uric acid dialysate concentrations. In rats given L‐DOPA either systemically or intrastriatally, intrastriatal infusion of manganese decreased L‐DOPA dialysate concentrations and greatly increased those of L‐DOPA semiquinone. These changes were inhibited by NAC infusion. These findings demonstrate that auto‐oxidation of exogenous L‐DOPA occurs in vivo in the rat striatum. The consequent reactive oxygen species generation may account for the decrease in dialysate DA and ascorbic acid concentrations and increase in enzymatic oxidation of xanthine and DA. L‐DOPA auto‐oxidation is inhibited by NAC and enhanced by manganese. These results may be of relevance to the L‐DOPA long‐term therapy of Parkinson's disease. British Journal of Pharmacology (2000) 130, 937–945; doi:10.1038/sj.bjp.0703379

The effects of systemic, intrastriatal or intranigral administration of d‐amphetamine on glutamate, aspartate, ascorbic acid (AA), uric acid, dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5‐hydroxyindoleacetic acid (5‐HIAA) concentrations in dialysates from the striatum of freely‐moving rats were evaluated using microdialysis. d‐Amphetamine (2 mg kg−1) given subcutaneously (s.c.) increased DA, AA and uric acid and decreased DOPAC+HVA, glutamate and aspartate dialysate concentrations over a 3 h period after d‐amphetamine. 5‐HIAA concentrations were unaffected. Individual changes in glutamate and AA dialysate concentrations were negatively correlated. d‐Amphetamine (0.2 mM), given intrastriatally, increased DA and decreased DOPAC+HVA and aspartate dialysate concentrations, but failed to change those of glutamate, AA uric acid or 5‐HIAA, over a 2 h period after d‐amphetamine. Haloperidol (0.1 mM), given intrastriatally, increased aspartate concentrations without affecting those of glutamate or AA. d‐Amphetamine (0.2 mM), given intranigrally, increased AA and uric acid dialysate concentrations and decreased those of glutamate, aspartate and DA; DOPAC+HVA and 5‐HIAA concentrations were unaffected. These results suggest that d‐amphetamine‐induced increases in AA and uric acid and decreases in glutamate concentrations are triggered at nigral sites. The changes in aspartate levels may be evoked by at least two mechanisms: striatal (mediated by inhibitory dopaminergic receptors) and nigral (activation of amino acid carrier‐mediated uptake). British Journal of Pharmacology (2000) 129, 582–588; doi:10.1038/sj.bjp.0703066

The effects of intrastriatal infusion of 3‐morpholinosydnonimine (SIN‐1) or sodium nitroprusside (SNP) on dopamine (DA), 3‐methoxytyramine (3‐MT), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), L‐dihydroxyphenylalanine (L‐DOPA), ascorbic acid and uric acid concentrations in dialysates from the striatum of freely moving rats were evaluated using microdialysis. SIN‐1 (1 mM) infusion for 180 min increased microdialysate DA and 3‐MT concentrations, while L‐DOPA, DOPCA+HVA, ascorbic acid and uric acid levels were unaffected. Co‐infusion with ascorbic acid (0.1 mM) inhibited SIN‐1‐induced increases in DA and 3‐MT dialysate concentration. SNP (1 mM) infusion for 180 min increased greatly the dialysate DA concentration to a peak (2950% of baseline) at the end of the infusion, while increases in 3‐MT were negligible. In addition, SNP decreased ascorbic acid and L‐DOPA but increased uric acid concentration in the dialysate. Co‐infusion with deferoxamine (0.2 mM) inhibited the late SNP‐induced increase in DA dialysate concentration, but did not affect the decrease in ascorbic acid and increase uric acid dialysate concentrations. SNP (1 mM) infusion for 20 min moderately increased uric acid, DA and 3‐MT, but decreased L‐DOPA levels in the dialysate. Ascorbic acid concentration increased at the end of SNP infusion. Co‐infusion with ascorbic acid (0.1 mM) inhibited the SNP‐induced increase in DA and 3‐MT, but did not affect the decrease in L‐DOPA and increase in uric acid dialysate concentrations. These results suggest that NO released from SIN‐1 may account for the increase in the dialysate DA concentration. NO released following decomposition of SNP may account for the early increase in dialysate DA, while late changes in microdialysate composition following SNP may result from an interaction between NO and the ferrocyanide moiety of SNP. Exogenous ascorbic acid inhibits the effect of exogenous NO on DA release probably by scavenging NO, suggesting that endogenous ascorbic acid may modulate the NO control of DA release from 300 striatal dopaminergic terminals. British Journal of Pharmacology (2000) 131, 836–842; doi:10.1038/sj.bjp.0703635

We showed previously that interaction between NO and iron (II), both released following the decomposition of sodium nitroprusside (SNP), accounted for the late SNP‐induced dopamine (DA) increase in dialysates from the striatum of freely moving rats; in addition, we showed that co‐infusion of iron (II) with the NO‐donor S‐nitroso‐N‐acetylpenicillamine mimicked SNP effects on striatal DA release. In the present study, intrastriatal co‐infusion of iron (II) (given as FeSO4, 1 mM for 40 min) with the NO‐donor and potential peroxynitrite generator 3‐morpholinosydnonimine (SIN‐1) (0.2, 0.5, 1.0 or 5.0 mM for 180 min), potentiated the SIN‐1‐induced increase in DA concentration in dialysates from the striatum of freely moving rats. Neither alone nor associated with iron (II) did SIN‐1 induce changes in dialysate ascorbic acid or uric acid concentrations. Neither co‐infusion of a superoxide dismutase mimetic nor uric acid affected SIN‐1‐induced increases in dialysate DA concentration. Infusion of the iron chelator deferoxamine (0.2 mM for 180 min) decreased dialysate DA and attenuated SIN‐1‐induced increases in dialysate DA concentrations. These results suggest that iron plays a key role in SIN‐1‐induced release of striatal DA and do not support any role for either peroxynitrite or superoxide anion in SIN‐1‐induced release of striatal DA. British Journal of Pharmacology (2001) 134, 275–282; doi:10.1038/sj.bjp.0704232

We showed previously that interaction between NO and iron(II), both released following decomposition of sodium nitroprusside (SNP), accounted for the late SNP‐induced dopamine (DA) increase in dialysates from the striatum of freely moving rats. In this study, intrastriatal infusion of the NO‐donor S‐nitroso‐N‐acetylpenicillamine (SNAP) (0.2 mM for 180 min) induced a moderate increase in dialysate DA and decreases in ascorbic acid dialysate concentrations; in contrast, SNAP 1 mM infusion induced a long‐lasting decrease in both DA and ascorbic acid dialysate concentrations. 3‐Methoxy‐tyramine (3‐MT), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and uric acid levels were unaffected. Co‐infusion of ferrous sulphate [iron(II), 1 mM for 40 min] with SNAP either 1 or 0.2 mM (for 180 min), produced a significant increase in both DA and 3‐MT dialysate concentrations, but it did not affect decreases in dialysate ascorbic acid levels. All other dialysate neurochemicals were unaffected. Co‐infusion of ascorbic acid (0.1 mM) with SNAP (1 mM) for 180 min did not modify SNAP‐induced decreases in dialysate DA levels. In contrast, co‐infusion of uric acid (1 mM) reversed SNAP‐induced decreases in dialysate DA; co‐infusion of a superoxide dismutase mimetic delayed SNAP‐induced DA decreases for a short period, while co‐infusion of the antioxidant N‐acetylcysteine (NAC, 0.1 mM) significantly increased dialysate DA. The results of this study show that SNAP induces concentration‐related changes in DA dialysate levels. At higher concentrations, SNAP induces non‐enzymatic DA oxidation, which is inhibited by uric acid and NAC; ascorbic acid failed to protect dialysate DA from oxidation, probably owing to its promoting effect on SNAP decomposition; exogenous iron(II) may react with NO generated from SNAP decomposition, with a consequent increase in dialysate DA and 3‐MT, therefore mimicking SNP effects on striatal DA release. British Journal of Pharmacology (2001) 132, 941–949; doi:10.1038/sj.bjp.0703887

The objective of the study is to evaluate the performance of solid cellular structures in Polylactic Acid (PLA) by extrusion of material. The structures studied are Strut-Based, Triply Periodic Minimal Surfaces (TPMS) and Spinoidal. Impact tests allowed the identification of three categories of energy absorption (low, medium, high). The structures with lower deformation were subsequently subjected to cyclic impact tests, while the others were discarded from the analysis. Once the structures were deformed, they were immersed in a thermostat bath at 70 ºC, a temperature higher than the glass transition of PLA, necessary for the recovery of shape. TPMS structures display the best performance for high and medium impact energies, thanks to the presence of few internal defects. Spinoidal structures perform well at low impact energies but are less suitable for cyclic testing due to their geometric characteristics. Despite featuring the same density of TPMS structures, the strut based ones are not suitable for cyclic testing due to poor mechanical strength. The experimental findings are very promising as the best performing structures can be suitable for the fabrication of products with an increased life cycle, especially in the ever growing and flourishing market of technical items for impacts protection.

This study aims to analyze the bending behavior of polylactic acid (PLA) structures made by fusion deposition modeling (FDM) technology. The investigation analyzed chiral structures such as lozenge and clepsydra, as well as geometries with wavy patterns such as roller and Es, in addition to a honeycomb structure. All geometries have a relative density of 50%. After being subjected to three-point bending tests, the capacity to spring back with respect to the bending angle and the shape recovery of the structures were measured. The roller and lozenge structures demonstrated the best performance, with shape recovery assessed through three consecutive hot water immersion cycles. The lozenge structure exhibits 25% higher energy absorption than the roller, but the latter ensures better replicability and shape stability. Additionally, the roller absorbs 15% less energy than the lozenge, which experiences a 27% decrease in absorption between the first and second cycle. This work provides new insights into the bending-based energy absorption and recovery behavior of PLA metamaterials, relevant for applications in adaptive and energy-dissipating systems.

This review paper presents a comprehensive analysis of the melt processing of polybutylene succinate (PBS) blends and composites. PBS, a biodegradable and eco-friendly thermoplastic polyester, has garnered significant interest in sustainable material research. The paper collates and examines a wide range of studies focusing on the processability, optimization of processing parameters, and resultant mechanical properties of PBS when processed through several extrusion techniques and by injection molding. Key parameters such as melt temperature, screw speed, and mold temperature are considered for their impact on the quality and performance of the final product. The review highlights advancements in processing technologies and material modifications that enhance PBS properties, making it a viable alternative to traditional petroleum-based plastics. Furthermore, challenges and limitations in the current processing techniques are discussed, offering insights into potential areas for future research. The synthesis of findings from various studies provides a holistic understanding of the state-of-the-art in PBS processing, aiming to guide further developments in the field of biodegradable polymers. Overall, this review underscores the importance of optimized melt processing techniques in maximizing the potential of PBS as a sustainable material in diverse applications. Graphical abstract

The present study investigates the behavior of solid cellular structures in polylactic acid (PLA) achieved by FDM technology (fusion deposition modelling). The geometries are permanently deformed by compressive stress and then subjected to shape recovery through the application of a thermal stimulus. The structures are submitted to medium–high and medium–low compression stresses, evaluating the mechanical properties and the absorption energy as the number of cycles varies. The study shows that the ability to absorb energy is related to the density of the model, as well as the degree of damage observed, which increases with increasing number of load cycles. The strongest geometry is the lozenge grid, which is the most reliable. It shows no damage with increasing compression cycles and keeps its capability to absorb energy almost constant. The increase in lozenge grid density leads to an improvement in both mechanical strength and absorption energy, as well as a lower incidence of microcracks in the geometry itself due to the repeated load cycles. These results open up a broad spectrum of applications of custom-designed solid cellular structures in the field of energy absorption and damping.