High-resolution head model of transcranial direct current stimulation: A labeling analysis

The ability of transcranial direct current stimulation (tDCS) to produce lasting polarity-specific modulatory effects continues to drive use both in research and clinical domains. Computational models of tDCS over the years have provided valuable insight on the current flow pattern and magnitude of electric field induced in the cortex. However, induced cortical values are usually not systematically quantified for different brain subcomponents that allow further investigation into the relevant contribution of these distinct regions. This information is of significant interest given different subcomponents of the brain contribute to different functions that ultimately underlie net outcomes. Thus given a particular stimulation response and the current flow pattern, one can potentially infer results in relation to current flow in different compartments (regions affected/spared, magnitude, etc.) The aim of this study is to determine tDCS induced electric field/current density using a high resolution head model incorporating a brain parcellated into 17 notable gyri and 10 sub-cortical regions. We consider both conventional tDCS and High Definition (HD)-tDCS electrode montages. The induced electrical field in each parcellated brain region is computed and compared across the two montages.Findings indicate that maximum electrical field is induced in the precentral gyrus for both the montages considered. As expected, the current flow pattern using the HD-tDCS montage considered is more restricted- both spatially and depth-wise. The conventional tDCS montage results in deeper current flow with sub-cortical structures subject to as much as 47-95% the current flow in the upper cortical regions. For the HD montage, electric field in the subcortical structures drop to 12-32% of the values induced in the upper regions. Incorporation of labeled human head models may guide rational electrode design and optimization of tDCS by providing more detailed and systematic information.

Transforming growth factor-beta 1 gene polymorphisms and expression in the blood of prostate cancer patients

The transforming growth factor beta 1 (TGF-beta1) is a multifunctional cytokine with several regulatory activities in tumor cells affecting growth, differentiation, and function. Alterations in gene expression, secretion, and regulation of TGF-beta1 may lead to a favorable environment for tumor development by angiogenesis stimulation and immune system suppression. We evaluated the influence of the TGFB1 polymorphisms by ARMS-PCR, Leu10Pro, and Arg25Pro, on prostate cancer (PCa) and benign prostatic hyperplasia (BPH). We assessed TGFB1 polymorphisms and their relation to mRNA levels (semi-quantitative RT-PCR) in blood samples as well as the implications in disease occurrence and progression. Peripheral blood samples from 175 patients were analyzed as to 92 BPH and 83 PCa. Samples obtained from 132 healthy males were used as negative controls. PCa patients with a Gleason score greater than 7 presented a higher frequency of the C allele (Leu10Pro). This allele was associated with a higher risk of developing PCa and BPH compared to the population (2.6 and 3.6 times higher, respectively). Patients with TGFB1 transcript levels equal to or more than 70% higher than control levels presented a 5.34 and 2.14-fold higher risk of having PCa and BPH, respectively, relative to the population. No association was detected between polymorphisms and mRNA levels. The C allele of the Leu10Pro polymorphism may predispose men to a more rapid cancer progression. Additionally, higher mRNA levels in the peripheral blood of PCa patients suggest that tumor cells may be disseminated in the circulation and could be used as a biomarker for extra-capsular invasion.