The sexually dimorphic expression of glutamate transporters and their implication in pain after spinal cord injury.

In addition to the loss of motor function, ~60% of patients develop pain after spinal cord injury. The cellular-molecular mechanisms are not well understood, but the data suggests that plasticity within the rostral, epicenter, and caudal penumbra of the injury site initiates a cellular-molecular interplay that acts as a rewiring mechanism leading to central neuropathic pain. Sprouting can lead to the formation of new connections triggering abnormal sensory transmission. The excitatory glutamate transporters are responsible for the reuptake of extracellular glutamate which makes them a critical target to prevent neuronal hyperexcitability and excitotoxicity. Our previous studies showed a sexually dimorphic therapeutic window for spinal cord injury after treatment with the selective estrogen receptor modulator tamoxifen. In this study, we investigated the anti-allodynic effects of tamoxifen in male and female rats with spinal cord injury. We hypothesized that tamoxifen exerts anti-allodynic effects by increasing the expression of glutamate transporters, leading to reduced hyperexcitability of the secondary neuron or by decreasing aberrant sprouting. Male and female rats received a moderate contusion to the thoracic spinal cord followed by subcutaneous slow-release treatment of tamoxifen or matrix pellets as a control (placebo). We used von Frey monofilaments and the "up-down method" to evaluate mechanical allodynia. Tamoxifen treatment decreased allodynia only in female rats with spinal cord injury revealing a sex-dependent effect. The expression profile of glutamatergic transporters (excitatory amino acid transporter 1/glutamate aspartate transporter and excitatory amino acid transporter 2/glutamate transporter-1) revealed a sexual dimorphism in the rostral, epicenter, and caudal areas of the spinal cord with a pattern of expression primarily on astrocytes. Female rodents showed a significantly higher level of excitatory amino acid transporter-1 expression while male rodents showed increased excitatory amino acid transporter-2 expression compared with female rodents. Analyses of peptidergic (calcitonin gene-related peptide-α) and non-peptidergic (isolectin B4) fibers outgrowth in the dorsal horn after spinal cord injury showed an increased calcitonin gene-related peptide-α/ isolectin B4 ratio in comparison with sham, suggesting increased receptive fields in the dorsal horn. Although the behavioral assay shows decreased allodynia in tamoxifen-treated female rats, this was not associated with overexpression of glutamate transporters or alterations in the dorsal horn laminae fibers at 28 days post-injury. Our findings provide new evidence of the sexually dimorphic expression of glutamate transporters in the spinal cord. The dimorphic expression revealed in this study provides a therapeutic opportunity for treating chronic pain, an area with a critical need for treatment.

The FMRF-NH2 gated sodium channel of Biomphalaria glabrata: Localization and expression following infection by Schistosoma mansoni.

The neglected tropical disease schistosomiasis impacts over 700 million people globally. Schistosoma mansoni, the trematode parasite that causes the most common type of schistosomiasis, requires planorbid pond snails of the genus Biomphalaria to support its larval development and transformation to the cercarial form that can infect humans. A greater understanding of neural signaling systems that are specific to the Biomphalaria intermediate host could lead to novel strategies for parasite or snail control. This study examined a Biomphalaria glabrata neural channel that is gated by the neuropeptide FMRF-NH2. The Biomphalaria glabrata FMRF-NH2 gated sodium channel (Bgl-FaNaC) amino acid sequence was highly conserved with FaNaCs found in related gastropods, especially the planorbid Planorbella trivolvis (91% sequence identity). In common with the P. trivolvis FaNaC, the B. glabrata channel exhibited a low affinity (EC50: 3 x 10-4 M) and high specificity for the FMRF-NH2 agonist. Its expression in the central nervous system, detected with immunohistochemistry and in situ hybridization, was widespread, with the protein localized mainly to neuronal fibers and the mRNA confined to cell bodies. Colocalization of the Bgl-FaNaC message with its FMRF-NH2 agonist precursor occurred in some neurons associated with male mating behavior. At the mRNA level, Bgl-FaNaC expression was decreased at 20 and 35 days post infection (dpi) by S. mansoni. Increased expression of the transcript encoding the FMRF-NH2 agonist at 35 dpi was proposed to reflect a compensatory response to decreased receptor levels. Altered FMRF-NH2 signaling could be vital for parasite proliferation in its intermediate host and may therefore present innovative opportunities for snail control.

Label-Free Telomerase Activity Detection via Electrochemical Impedance Spectroscopy.

In the last decade, researchers have been searching for innovative platforms, methods, and techniques able to address recurring problems with the current cancer detection methods. Early disease detection, fast results, point-of-care sensing, and cost are among the most prevalent issues that need further exploration in this field. Herein, studies are focused on overcoming these problems by developing an electrochemical device able to detect telomerase as a cancer biomarker. Electrochemical platforms and techniques are more appealing for cancer detection, offering lower costs than the established cancer detection methods, high sensitivity inherent to the technique, rapid signal processing, and their capacity of being miniaturized. Therefore, Au interdigital electrodes and electrochemical impedance spectroscopy were used to detect telomerase activity in acute T cell leukemia. Different cancer cell concentrations were evaluated, and a detection limit of 1.9 × 105 cells/mL was obtained. X-ray photoelectron spectroscopy was used to characterize the telomerase substrate (TS) DNA probe self-assembled monolayer on gold electrode surfaces. Atomic force microscopy displayed three-dimensional images of the surface to establish a height difference of 9.0 nm between the bare electrode and TS-modified Au electrodes. The TS probe is rich in guanines, thus forming secondary structures known as G-quadruplex that can be triggered with a fluorescence probe. Confocal microscopy fluorescence images showed the formation of DNA G-quadruplex because of TS elongation by telomerase on the Au electrode surface. Moreover, electrodes exposed to telomerase containing 2',3'-dideoxyguanosine-5'-triphosphate (ddGTP) did not exhibit high fluorescence, as ddGTP is a telomerase inhibitor, thus making this device suitable for telomerase inhibitors capacity studies. The electrochemical method and Au microchip device may be developed as a biosensor for a point-of-care medical device.

Biocompatible ZnS:Mn quantum dots for reactive oxygen generation and detection in aqueous media.

ABSTRACT: We report here the versatility of Mn-doped ZnS quantum dots (ZnS:Mn QDs) synthesized in aqueous medium for generating reactive oxygen species and for detecting cells. Our experiments provide evidence leading to the elimination of Cd-based cores in CdSe/ZnS systems by substitution of Mn-doped ZnS. Advanced electron microscopy, X-ray diffraction, and optical spectroscopy were applied to elucidate the formation, morphology, and dispersion of the products. We study for the first time the ability of ZnS:Mn QDs to act as immobilizing agents for Tyrosinase (Tyr) enzyme. It was found that ZnS:Mn QDs show no deactivation of Tyr enzyme, which efficiently catalyzed the hydrogen peroxide (H2O2) oxidation and its eventual reduction (-0.063 V vs. Ag/AgCl) on the biosensor surface. The biosensor showed a linear response in the range of 12 µmol/L-0.1 mmol/L at low operation potential. Our observations are explained in terms of a catalase-cycled kinetic mechanism based on the binding of H2O2 to the axial position of one of the active copper sites of the oxy-Tyr during the catalase cycle to produce deoxy-Tyr. A singlet oxygen quantum yield of 0.62 in buffer and 0.54 in water was found when ZnS:Mn QDs were employed as a photosensitizer in the presence of a chemical scavenger and a standard dye. These results are consistent with a chemical trapping energy transfer mechanism. Our results also indicate that ZnS:Mn QDs are well tolerated by HeLa Cells reaching cell viabilities as high as 88 % at 300 µg/mL of QDs for 24 h of incubation. The ability of ZnS:Mn QDs as luminescent nanoprobes for bioimaging is also discussed.