scholarly journals Determination of anodal tDCS duration threshold for reversal of corticospinal excitability: An investigation for induction of counter-regulatory mechanisms

2020 ◽  
Vol 13 (3) ◽  
pp. 832-839 ◽  
Author(s):  
Maryam Hassanzahraee ◽  
Michael A. Nitsche ◽  
Maryam Zoghi ◽  
Shapour Jaberzadeh
Keyword(s):  
Corticospinal Excitability ◽  
Regulatory Mechanisms ◽  
Anodal Tdcs ◽  
Duration Threshold

scholarly journals Determination of anodal tDCS intensity threshold for reversal of corticospinal excitability: an investigation for induction of counter-regulatory mechanisms

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maryam Hassanzahraee ◽  
Michael A. Nitsche ◽  
Maryam Zoghi ◽  
Shapour Jaberzadeh
Keyword(s):  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Single Pulse ◽  
Random Order ◽  
Corticospinal Excitability ◽  
Regulatory Mechanisms ◽  
Anodal Tdcs ◽  
Post Intervention ◽  
Stimulation Intensity ◽  
Intensity Threshold

Abstract Transcranial direct current stimulation is applied to modulate activity, and excitability of the brain. Basically, LTP-like plasticity is induced when anodal tDCS (a-tDCS) is applied over the primary motor cortex. However, it has been shown that specific parameters of a-tDCS can induce a plasticity reversal. We aimed to systematically assess the intensity threshold for reversal of the direction of plasticity induced by a-tDCS, monitored by corticospinal excitability (CSE), and explored mechanisms regulating this reversal. Fifteen healthy participants received a-tDCS in pseudo-random order for 26 min with four intensities of 0.3, 0.7, 1, and 1.5 mA. To measure CSE changes, single-pulse TMS was applied over the left M1, and motor evoked potentials of a contralateral hand muscle were recorded prior to a-tDCS, immediately and 30-min post-intervention. Paired-pulse TMS was used to evaluate intracortical excitation and inhibition. CSE increased significantly following a-tDCS with an intensity of 0.7 mA; however, the expected effect decreased and even reversed at intensities of 1 and 1.5 mA. ICF was significantly increased while SICI and LICI decreased at 0.7 mA. On the other hand, a significant decrease of ICF, but SICI and LICI enhancement was observed at intensities of 1, and 1.5 mA. The present findings show an intensity threshold of ≥ 1 mA for 26 min a-tDCS to reverse LTP- into LTD-like plasticity. It is suggested that increasing stimulation intensity, with constant stimulation duration, activates counter-regulatory mechanisms to prevent excessive brain excitation. Therefore, stimulation intensity and plasticity induced by a-tDCS might non-linearly correlate in scenarios with prolonged stimulation duration.

Sporulation and peroxidase in Bipolaris maydis: effects of xylose and thiamine

1977 ◽  
Vol 55 (14) ◽  
pp. 1996-2000 ◽  
Author(s):  
M. O. Garraway ◽  
R. C. Evans
Keyword(s):  
Quantitative Determination ◽  
Peroxidase Activity ◽  
Inverse Relationship ◽  
Agar Medium ◽  
Phenol Concentration ◽  
Regulatory Mechanisms ◽  
Mineral Salts ◽  
Bipolaris Maydis ◽  
The Media

Sporulation of the fungus Bipolaris maydis increased and peroxidase (EC 1.11.1.7) activity decreased when xylose was added as a supplement to a basal glucose – mineral salts – agar medium containing either L-asparagine or NaNO3. With L-asparagine, thiamine–HCl (1.0 mg/ℓ) caused a significant decrease in sporulation and an increase in peroxidase activity. The magnitude of the decrease induced by thiamine–HCl in sporulation and increase in residue peroxidase activity appeared greater on a non-supplemented medium than on one supplemented with xylose. With NaNO3, the magnitude of the decrease in sporulation induced by 0.1 mg/ℓ thiamine–HCl appeared comparable whether or not the medium was supplemented with xylose, but the magnitude of the increase in residue peroxidase activity was greater without than with xylose. Quantitative determination of intracellular phenols as possible substrates for peroxidase revealed that there was no change in total phenol concentration regardless of the xylose and thiamine–HCl content of the media. The apparent inverse relationship between sporulation and peroxidase activity in B. maydis provides clues to the specific regulatory mechanisms involved in sporulation.

scholarly journals Multimodal Assessment of Precentral Anodal TDCS: Individual Rise in Supplementary Motor Activity Scales With Increase in Corticospinal Excitability

2021 ◽  
Vol 15 ◽  
Author(s):  
Anke Ninija Karabanov ◽  
Keiichiro Shindo ◽  
Yuko Shindo ◽  
Estelle Raffin ◽  
Hartwig Roman Siebner
Keyword(s):  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Single Pulse ◽  
Individual Variability ◽  
Corticospinal Excitability ◽  
Anodal Tdcs ◽  
Related Activity ◽  
Whole Brain ◽  
After Effects ◽  
Visuomotor Tracking

BackgroundTranscranial direct current stimulation (TDCS) targeting the primary motor hand area (M1-HAND) may induce lasting shifts in corticospinal excitability, but after-effects show substantial inter-individual variability. Functional magnetic resonance imaging (fMRI) can probe after-effects of TDCS on regional neural activity on a whole-brain level.ObjectiveUsing a double-blinded cross-over design, we investigated whether the individual change in corticospinal excitability after TDCS of M1-HAND is associated with changes in task-related regional activity in cortical motor areas.MethodsSeventeen healthy volunteers (10 women) received 20 min of real (0.75 mA) or sham TDCS on separate days in randomized order. Real and sham TDCS used the classic bipolar set-up with the anode placed over right M1-HAND. Before and after each TDCS session, we recorded motor evoked potentials (MEP) from the relaxed left first dorsal interosseus muscle after single-pulse transcranial magnetic stimulation(TMS) of left M1-HAND and performed whole-brain fMRI at 3 Tesla while participants completed a visuomotor tracking task with their left hand. We also assessed the difference in MEP latency when applying anterior-posterior and latero-medial TMS pulses to the precentral hand knob (AP-LM MEP latency).ResultsReal TDCS had no consistent aftereffects on mean MEP amplitude, task-related activity or motor performance. Individual changes in MEP amplitude, measured directly after real TDCS showed a positive linear relationship with individual changes in task-related activity in the supplementary motor area and AP-LM MEP latency.ConclusionFunctional aftereffects of classical bipolar anodal TDCS of M1-HAND on the motor system vary substantially across individuals. Physiological features upstream from the primary motor cortex may determine how anodal TDCS changes corticospinal excitability.

scholarly journals Speech Induced Changes in Corticospinal Excitability. Determination of dominant hemisphere with single magnetic stimulation.

1999 ◽  
Vol 19 (2) ◽  
pp. 128-135
Author(s):  
Hiroshi Tokimura ◽  
Hirofumi Hamada ◽  
Tetsuhiko Asakura ◽  
John C. Rothwell
Keyword(s):  
Magnetic Stimulation ◽  
Corticospinal Excitability ◽  
Dominant Hemisphere ◽  
Induced Changes

scholarly journals 5-Fluorouracil: A Narrative Review on the Role of Regulatory Mechanisms in Driving Resistance to This Chemotherapeutic Agent

2021 ◽  
Vol 11 ◽  
Author(s):  
Soudeh Ghafouri-Fard ◽  
Atefe Abak ◽  
Farhad Tondro Anamag ◽  
Hamed Shoorei ◽  
Faranak Fattahi ◽  
...  
Keyword(s):  
Tumor Cells ◽  
Epithelial Mesenchymal Transition ◽  
Chemotherapeutic Agent ◽  
Chemotherapeutic Agents ◽  
Regulatory Mechanisms ◽  
Cell Behavior ◽  
Mesenchymal Transition ◽  
Non Coding Rnas

5-fluorouracil (5-FU) is among the mostly administrated chemotherapeutic agents for a wide variety of neoplasms. Non-coding RNAs have a central impact on the determination of the response of patients to 5-FU. These transcripts via modulation of cancer-related pathways, cell apoptosis, autophagy, epithelial–mesenchymal transition, and other aspects of cell behavior can affect cell response to 5-FU. Modulation of expression levels of microRNAs or long non-coding RNAs may be a suitable approach to sensitize tumor cells to 5-FU treatment via modulating multiple biological signaling pathways such as Hippo/YAP, Wnt/β-catenin, Hedgehog, NF-kB, and Notch cascades. Moreover, there is an increasing interest in targeting these transcripts in various kinds of cancers that are treated by 5-FU. In the present article, we provide a review of the function of non-coding transcripts in the modulation of response of neoplastic cells to 5-FU.

scholarly journals Regulation of GH Secretion in Acromegaly: Reproducibility of Daily GH Profiles and Attenuated Negative Feedback by IGF-I

2001 ◽  
Vol 86 (9) ◽  
pp. 4364-4370 ◽  
Author(s):  
Craig A. Jaffe ◽  
Wenqin Pan ◽  
Morton B. Brown ◽  
Roberta DeMott-Friberg ◽  
Ariel L. Barkan
Keyword(s):  
Negative Feedback ◽  
Feedback Regulation ◽  
Secretory Activity ◽  
Regulatory Mechanisms ◽  
Newly Diagnosed ◽  
Negative Feedback Regulation ◽  
Gh Secretion ◽  
Igf I ◽  
Cross Correlations

GH hypersecretion is a hallmark of acromegaly. It is unknown whether the secretory activity of somatotroph adenoma is autonomous or is still governed by central or peripheral mechanisms. In this study we investigated whether GH secretion in acromegaly 1) has a reproducible circadian pattern and 2) is inhibited by exogenous IGF-I. Eleven patients with newly diagnosed acromegaly were studied in 2 protocols. In protocol 1, peripheral blood was sampled every 10 min for 48 h in 6 patients for the determination of concordance between 24-h GH profiles. There was no significant day to day variability in mean 24-h output. There was, however, a significant time effect, and the 24-h GH secretion pattern was maintained between days. In protocol 2, 5 patients were sampled for GH every 10 min twice, once during infusion of normal saline and once during iv infusion of recombinant human IGF-I (10 μg/kg·h). The recombinant human IGF-I infusion increased plasma IGF-I to approximately 230% of the baseline concentration. This resulted in GH suppression (4220 ± 1950 vs. 3223 ± 1472 μg/liter·min; P = 0.001), but did not alter GH secretion pattern. There were highly significant cross-correlations for 10 of the 11 of the subjects in the two protocols when the lag was 0 min. By harmonic analysis, nocturnal augmentation of GH was maintained, and maximum daily GH occurred at approximately 2300 h. These data demonstrate that the pattern of GH secretion in acromegaly is not random, but is highly preserved with 24-h periodicity. In addition, negative feedback regulation by IGF-I is preserved, although the degree of negative feedback is grossly attenuated. Thus, secretory activity of somatotroph adenomas is not autonomous or haphazard, but is still subject to both feedback and feedforward regulatory mechanisms.

scholarly journals Preconditioning cathodal transcranial direct current stimulation facilitates the neuroplastic effect of subsequent anodal transcranial direct current stimulation applied during cycling in young adults

2019 ◽  
Author(s):  
Maryam Pourmajidian ◽  
Benedikt Lauber ◽  
Simranjit K Sidhu
Keyword(s):  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Motor Evoked Potentials ◽  
Corticospinal Excitability ◽  
Anodal Tdcs ◽  
Double Blind ◽  
Cycling Exercise ◽  
Direct Current Stimulation ◽  
Post Test ◽  
Double Blind Design

AbstractThe study aimed to examine the effect of a priming cathodal transcranial direct current stimulation (ctDCS) before subsequent anodal-tDCS (atDCS) was applied during low workload cycling exercise on the corticospinal responses in young healthy individuals. Eleven young subjects participated in two sessions receiving either priming ctDCS or sham stimulation, followed by atDCS while cycling (i.e. ctDCS-atDCS, sham-atDCS) at 1.2 times their body weight (84 ± 20 W) in a counterbalanced double-blind design. Corticospinal excitability was measured with motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation with the intensity set to produce an MEP amplitude of 1 mV in a resting hand muscle at baseline (PRE), following priming tDCS (POST-PRIMING) and post atDCS combined with cycling exercise (POST-TEST). There was a significant interaction between time and intervention (P < 0.01) on MEPs. MEPs increased from PRE (1.0 ± 0.06 mV) to POST-TEST (1.3 ± 0.06 mV) during ctDCS-atDCS (P < 0.001) but did not change across time during sham-atDCS (1.0 ± 0.06 mV, P > 0.7). Furthermore, MEPs were higher in ctDCS-atDCS compared to sham-atDCS (P < 0.01) at both POST-PRIMING (ctDCS-atDCS: 1.1 ± 0.06, sham-atDCS: 1.0 ± 0.06) and POST-TEST (ctDCS-atDCS: 1.3 ± 0.06, sham-atDCS: 1.0 ± 0.06). These outcomes demonstrate that cathodal tDCS priming can enhance corticospinal excitability following anodal tDCS applied in combination with cycling exercise. The findings have implications for the application of tDCS in combination with cycling exercise in rehabilitation and sporting contexts.

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