Analysis of fractal electrodes for efficient neural stimulation

Planar electrodes are increasingly used in therapeutic neural stimulation techniques such as functional electrical stimulation, epidural spinal cord stimulation (ESCS), and cortical stimulation. Recently, optimized electrode geometries have been shown to increase the efficiency of neural stimulation by increasing the variation of current density on the electrode surface. In the present work, a new family of modified fractal electrode geometries is developed to enhance the efficiency of neural stimulation. It is shown that a promising approach in increasing the neural activation function is to increase the "edginess" of the electrode surface, a concept that is explained and quantified by fractal mathematics. Rigorous finite element simulations were performed to compute electric potential produced by proposed modified fractal geometries. The activation of 256 model axons positioned around the electrodes was then quantified, showing that modified fractal geometries required a 22% less input power while maintaining the same level of neural activation. Preliminary in vivo experiments investigating muscle evoked potentials due to median nerve stimulation showed encouraging results, supporting the feasibility of increasing neural stimulation efficiency using modified fractal geometries.

Specific and reversible immobilization of proteins tagged to the affinity polypeptide C-LytA on functionalized graphite electrodes

We have developed a general method for the specific and reversible immobilization of proteins fused to the choline-binding module C-LytA on functionalized graphite electrodes. Graphite electrode surfaces were modified by diazonium chemistry to introduce carboxylic groups that were subsequently used to anchor mixed self-assembled monolayers consisting of N,N-diethylethylenediamine groups, acting as choline analogs, and ethanolamine groups as spacers. The ability of the prepared electrodes to specifically bind C-LytA-tagged recombinant proteins was tested with a C-LytA-β-galactosidase fusion protein. The binding, activity and stability of the immobilized protein was evaluated by electrochemically monitoring the formation of an electroactive product in the enzymatic hydrolysis of the synthetic substrate 4-aminophenyl β-D-galactopyranoside. The hybrid protein was immobilized in an specific and reversible way, while retaining the catalytic activity. Moreover, these functionalized electrodes were shown to be highly stable and reusable. The method developed here can be envisaged as a general, immobilization procedure on the protein biosensor field.

An electroanalytical application of 2-aminothiazole-modified silica gel after adsorption and separation of Hg(II) from heavy metals in aqueous solution

2-Aminothiazole covalently attached to a silica gel surface was prepared in order to obtain an adsorbent for Hg(II) ions having the following characteristics: good sorption capacity, chemical stability under conditions of use, and, especially, high selectivity. The accumulation voltammetry of mercury(II) was investigated at a carbon paste electrode chemically modified with silica gel functionalized with 2-aminothiazole (SIAMT-CPE). The repetitive cyclic voltammogram of mercury(II) solution in the potential range -0.2 to + 0.6 V versus Ag/AgCl (0.02 mol L-1 KNO3; V = 20 mV s(-1)) show two peaks one at about 0.1 V and other at 0.205 V. The anodic wave peak at 0.205 V is well defined and does not change during the cycles and it was therefore further investigated for analytical purposes using differential pulse anodic stripping voltammetry in differents supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. The precision for six determinations (n = 6) of 0.02 and 0.20 mg L-1 Hg(II) was 4.1 and 3.5% (relative standard deviation), respectively. The detection limit was estimated as 0.10 mu g L-1 mercury(II) by means of 3:1 current-to-noise ratio in connection with the optimization of the various parameters involved and using the highest-possible analyser sensitivity. (c) 2006 Elsevier Ltd. All rights reserved.

The Value Of The 2005 International Society Of Urological Pathology (isup) Modified Gleason Grading System As A Predictor Of Biochemical Recurrence After Radical Prostatectomy.

To compare time and risk to biochemical recurrence (BR) after radical prostatectomy of two chronologically different groups of patients using the standard and the modified Gleason system (MGS). Cohort 1 comprised biopsies of 197 patients graded according to the standard Gleason system (SGS) in the period 1997/2004, and cohort 2, 176 biopsies graded according to the modified system in the period 2005/2011. Time to BR was analyzed with the Kaplan-Meier product-limit analysis and prediction of shorter time to recurrence using univariate and multivariate Cox proportional hazards model. Patients in cohort 2 reflected time-related changes: striking increase in clinical stage T1c, systematic use of extended biopsies, and lower percentage of total length of cancer in millimeter in all cores. The MGS used in cohort 2 showed fewer biopsies with Gleason score ≤ 6 and more biopsies of the intermediate Gleason score 7. Time to BR using the Kaplan-Meier curves showed statistical significance using the MGS in cohort 2, but not the SGS in cohort 1. Only the MGS predicted shorter time to BR on univariate analysis and on multivariate analysis was an independent predictor. The results favor that the 2005 International Society of Urological Pathology modified system is a refinement of the Gleason grading and valuable for contemporary clinical practice.

Electronic And Structural Study Of Pt-modified Au Vicinal Surfaces: A Model System For Pt-au Catalysts.

Two single crystalline surfaces of Au vicinal to the (111) plane were modified with Pt and studied using scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) in ultra-high vacuum environment. The vicinal surfaces studied are Au(332) and Au(887) and different Pt coverage (θPt) were deposited on each surface. From STM images we determine that Pt deposits on both surfaces as nanoislands with heights ranging from 1 ML to 3 ML depending on θPt. On both surfaces the early growth of Pt ad-islands occurs at the lower part of the step edge, with Pt ad-atoms being incorporated into the steps in some cases. XPS results indicate that partial alloying of Pt occurs at the interface at room temperature and at all coverage, as suggested by the negative chemical shift of Pt 4f core line, indicating an upward shift of the d-band center of the alloyed Pt. Also, the existence of a segregated Pt phase especially at higher coverage is detected by XPS. Sample annealing indicates that the temperature rise promotes a further incorporation of Pt atoms into the Au substrate as supported by STM and XPS results. Additionally, the catalytic activity of different PtAu systems reported in the literature for some electrochemical reactions is discussed considering our findings.

A Modified Acidic Approach For Dna Extraction From Plant Species Containing High Levels Of Secondary Metabolites.

Purified genomic DNA can be difficult to obtain from some plant species because of the presence of impurities such as polysaccharides, which are often co-extracted with DNA. In this study, we developed a fast, simple, and low-cost protocol for extracting DNA from plants containing high levels of secondary metabolites. This protocol does not require the use of volatile toxic reagents such as mercaptoethanol, chloroform, or phenol and allows the extraction of high-quality DNA from wild and cultivated tropical species.

Remediation Of 17-α-ethinylestradiol Aqueous Solution By Photocatalysis And Electrochemically-assisted Photocatalysis Using Tio2 And Tio2/wo3 Electrodes Irradiated By A Solar Simulator.

TiO2 and TiO2/WO3 electrodes, irradiated by a solar simulator in configurations for heterogeneous photocatalysis (HP) and electrochemically-assisted HP (EHP), were used to remediate aqueous solutions containing 10 mg L(-1) (34 μmol L(-1)) of 17-α-ethinylestradiol (EE2), active component of most oral contraceptives. The photocatalysts consisted of 4.5 μm thick porous films of TiO2 and TiO2/WO3 (molar ratio W/Ti of 12%) deposited on transparent electrodes from aqueous suspensions of TiO2 particles and WO3 precursors, followed by thermal treatment at 450 (°)C. First, an energy diagram was organized with photoelectrochemical and UV-Vis absorption spectroscopy data and revealed that EE2 could be directly oxidized by the photogenerated holes at the semiconductor surfaces, considering the relative HOMO level for EE2 and the semiconductor valence band edges. Also, for the irradiated hybrid photocatalyst, electrons in TiO2 should be transferred to WO3 conduction band, while holes move toward TiO2 valence band, improving charge separation. The remediated EE2 solutions were analyzed by fluorescence, HPLC and total organic carbon measurements. As expected from the energy diagram, both photocatalysts promoted the EE2 oxidation in HP configuration; after 4 h, the EE2 concentration decayed to 6.2 mg L(-1) (35% of EE2 removal) with irradiated TiO2 while TiO2/WO3 electrode resulted in 45% EE2 removal. A higher performance was achieved in EHP systems, when a Pt wire was introduced as a counter-electrode and the photoelectrodes were biased at +0.7 V; then, the EE2 removal corresponded to 48 and 54% for the TiO2 and TiO2/WO3, respectively. The hybrid TiO2/WO3, when compared to TiO2 electrode, exhibited enhanced sunlight harvesting and improved separation of photogenerated charge carriers, resulting in higher performance for removing this contaminant of emerging concern from aqueous solution.

[the Modified Us7 Score In The Assessment Of Synovitis In Early Rheumatoid Arthritis].

To evaluate the modified US7 score (MUS7 score SYN) in the assessment of patients with early rheumatoid arthritis (ERA). In addition, dorsal and palmar recesses of the wrists as well as of small joints of the hands and feet were examined for the presence of synovitis by means of a global assessment of joints. The study sample comprised 32 patients treated for arthritis, with an average disease duration of 13 months. An ultrasound machine with high frequency transducer was used. Hands were also X-rayed and analysed by Larsen score. Out of the 832 examined joints, synovitis was detected in 173 (20,79%), tenosynovitis in 22 (4,91%), and erosions in 3 (1,56%). Synovitis was predominantly detected in the dorsal recess (73,38%) of MCP and PIP joints, when compared with palmar recess (26%). The presence of synovitis in the joints evaluated correlated with clinical (HAQ-DI, DAS28), laboratory (ACPA, RF, CRP), and ultrasound results (r = 0,37 to r = 0,42; p = 0,04 to p = 0,003). We found correlation of the MUS7 score SYN of the gray scale US or of the power Doppler US with DAS28 (PCR) values (r = 0,38; p = 0,0332), and with CRP results (r = 0,39; p = 0,0280), respectively. The dorsal recess, the wrist, and small joints can be considered as important sites to detect synovitis by the MUS7 score SYN in patients with ERA.

Didanosine-loaded Chitosan Microspheres Optimized By Surface-response Methodology: A Modified Maximum Likelihood Classification" Approach Formulation For Reverse Transcriptase Inhibitors."

Didanosine-loaded chitosan microspheres were developed applying a surface-response methodology and using a modified Maximum Likelihood Classification. The operational conditions were optimized with the aim of maintaining the active form of didanosine (ddI), which is sensitive to acid pH, and to develop a modified and mucoadhesive formulation. The loading of the drug within the chitosan microspheres was carried out by ionotropic gelation technique with sodium tripolyphosphate (TPP) as cross-linking agent and magnesium hydroxide (Mg(OH)2) to assure the stability of ddI. The optimization conditions were set using a surface-response methodology and applying the Maximum Likelihood Classification, where the initial chitosan concentration, TPP and ddI concentration were set as the independent variables. The maximum ddI-loaded in microspheres (i.e. 1433mg of ddI/g chitosan), was obtained with 2% (w/v) chitosan and 10% TPP. The microspheres depicted an average diameter of 11.42μm and ddI was gradually released during 2h in simulated enteric fluid.

Salivary Bpifa1 (splunc1) And Bpifa2 (splunc2 A) Are Modified By Head And Neck Cancer Radiotherapy.

To determine the effects of radiotherapy on salivary BPIFA expression and to investigate the role of BPIFA in the development of known radiotherapy side effects. Unstimulated whole-mouth saliva was collected from 45 cancer patients (1 week before treatment, during the treatment, and 1 week after completion of radiotherapy) and from 20 controls. BPIFA1 and BPIFA2 expression was detected by western blotting and analyzed along with clinicopathologic data and side effects from the radiotherapy. A facial radiation field was associated with lower salivary flow during and after radiotherapy and correlated with side effects, mainly mucositis. Salivary BPIFA1 expression levels were similar between the control group and the patient group before treatment. On the other hand, BPIFA2 levels were higher in the patient group before treatment compared with the control group. BPIFA concentration was modified by radiotherapy as BPIFA1 levels increased (P = .0081) and BPIFA2 decreased (P < .0001). Higher levels of BPIFA1 were associated with the presence of mucositis (P = .0363) and its severity (P = .0500). The present study found that levels of BPIFA1 and glycosylated forms of BPIFA2 are affected by radiotherapy, suggesting that these proteins may play a role in the oral microenvironment in irradiated patients with head and neck cancer.

Fluoride release profile of a nanofilled resin-modified glass ionomer cement

The present study aimed to compare the fluoride (F-) release pattern of a nanofilled resin-modified glass ionomer cement (GIC) (Ketac N100 - KN) with available GICs used in dental practice (resin-modified GIC - Vitremer - V; conventional GIC - Ketac Molar - KM) and a nanofilled resin composite (Filtek Supreme - RC). Discs of each material (n=6) were placed into 4 mL of deionized water in sealed polyethylene vials and shaken, for 15 days. F- release (μg F-/cm²) was measured each day using a fluoride-ion specific electrode. Cumulative F- release means were statistically analyzed by linear regression analysis. In order to analyze the differences among materials and the influence of time in the daily F- release, 2-way ANOVA test was performed (α=0.05). The linear fits between the cumulative F- release profiles of RC and KM and time were weak. KN and V presented a strong relationship between cumulative F- release and time. There were significant differences between the daily F- release overtime up to the third day only for GICs materials. The daily F- release means for RC were similar overtime. The results indicate that the F- release profile of the nanofilled resin-modified GIC is comparable to the resin-modified GIC.

Rehabilitation of severely resorbed edentulous mandible using the modified visor osteotomy technique

The prosthetic rehabilitation of an atrophic mandible is usually unsatisfactory due to the lack of support tissues, mainly bone and keratinized mucosa for treatment with osseointegrated implants or even conventional prosthesis. The prosthetic instability leads to social and functional limitations and chronic physical trauma decreasing the patient's quality of life. A 53-year-old female patient sought care at our surgical service complaining of impairment of her masticatory function associated with the instability of the lower total prosthetic denture. The clinical and complementary exams revealed edentulism in both arches, while the mandibular arch presented severe reabsorption resulting in denture instability and chronic trauma to the oral mucosa. The proposed treatment plan consisted in the mandibular rehabilitation with osseointegrated implants and fixed Brånemark's protocol prosthesis after mandibular reconstruction applying the modified visor osteotomy technique. The proposed technique offered predictable results for reconstruction of the severely resorbed edentulous mandible and posterior rehabilitation with osseointegrated implants.

Medidas operantes de limiar auditivo em crianças com surdez pré-lingual, usuárias de implante coclear

Limiares auditivos de crianças surdas pré-linguais usuárias de implante coclear foram avaliados com estimulação elétrica em um dos eletrodos mediais. A avaliação empregou um procedimento operante do tipo go/no go para ensinar uma discriminação simples, evidenciada por uma resposta motora, entre presença e ausência do estímulo auditivo. Estabelecida a linha de base, a manipulação na intensidade do estímulo foi implementada de acordo com o método psicofísico de escada modificado, começando por uma seqüência descendente. Os sete participantes do estudo mostraram perda da precisão no responder sob controle do estímulo quando a intensidade diminuía além de um certo valor e a precisão era recuperada quando a intensidade era novamente aumentada, o que permitiu a identificação de limiares individuais. Os resultados sugerem que o método psicofísico combinado com o procedimento operante pode ser uma alternativa viável para avaliar limiar auditivo de pessoas sem linguagem em situação clínica de regulagem do implante coclear.

Antibacterial modified diketopiperazines from two ascidians of the genus Didemnum

The chemical investigation of the crude extract of an ascidian of the genus Didemnumled to the isolation of the modified diketopiperazine rodriguesines A (1) and (2) as a mixture of homologues, which could be identified by analysis of spectroscopic data including MS/MS experiments. The investigation of a second Didemnumsp. led to the isolation of N-acetyl-rodriguesine A (3) and N-acetyl-rodriguesine B (4). The absolute configuration of compounds 1and 2could be established by hydrolysis and Marfey's analysis and comparison with literature data reported for compound 3, previously obtained as a synthetic product. The mixture of 1and 2displayed moderate antibiotic activity against a clinical isolate of Streptococcus mutansand against S. mutansUA159 and Staphylococcus aureusATCC6538.

Rat pinealectomy: a modified direct visual approach

PURPOSE: To report a new, direct visual approach for rat pinealectomy. METHODS: Eighty adult female rats (Rattus norvegicus albinus EPM-1 strain) were weighted and anesthetized intraperitoneally with 15 mg/kg xylazine and 30 mg/kg ketamine. The animal was fastened to a dissection table, an incision was made in the skin and the subcutaneous tissue, bringing the lambda into view. The skullcap was opened with a dental drill, bringing the cerebral hemispheres and the superior sagittal sinus into view. The pineal gland, located under the venous sinus, was removed in a single piece using tweezers. Next, the bone fragment was returned to its place and the surgical layers were sutured. RESULTS: This new technique is easy to be done, avoids bleedings and removes only the pineal gland without damage to the remaining encephalon. In addition it makes possible the achievement of a sham surgery, allowing the pineal gland to remain intact. CONCLUSION: The proposed technique intends to facilitate studies aiming to better understanding the complexity and importance of the pineal gland on reproductive and other body systems.