137 research outputs found
Long-Lasting Enhancement of Visual Perception with Repetitive Noninvasive Transcranial Direct Current Stimulation
Understanding processes performed by an intact visual cortex as the basis for
developing methods that enhance or restore visual perception is of great
interest to both researchers and medical practitioners. Here, we explore
whether contrast sensitivity, a main function of the primary visual cortex
(V1), can be improved in healthy subjects by repetitive, noninvasive anodal
transcranial direct current stimulation (tDCS). Contrast perception was
measured via threshold perimetry directly before and after intervention (tDCS
or sham stimulation) on each day over 5 consecutive days (24 subjects, double-
blind study). tDCS improved contrast sensitivity from the second day onwards,
with significant effects lasting 24 h. After the last stimulation on day 5,
the anodal group showed a significantly greater improvement in contrast
perception than the sham group (23 vs. 5%). We found significant long-term
effects in only the central 2–4° of the visual field 4 weeks after the last
stimulation. We suspect a combination of two factors contributes to these
lasting effects. First, the V1 area that represents the central retina was
located closer to the polarization electrode, resulting in higher current
density. Second, the central visual field is represented by a larger cortical
area relative to the peripheral visual field (cortical magnification). This is
the first study showing that tDCS over V1 enhances contrast perception in
healthy subjects for several weeks. This study contributes to the
investigation of the causal relationship between the external modulation of
neuronal membrane potential and behavior (in our case, visual perception).
Because the vast majority of human studies only show temporary effects after
single tDCS sessions targeting the visual system, our study underpins the
potential for lasting effects of repetitive tDCS-induced modulation of
neuronal excitability
Numerical Investigations on Stresses and Temperature Development of Tool Dies During Hot Forging
Hot-forming tools are subjected to high thermal and mechanical stresses during their application. Therefore, a suitable design of the tool die is important to ensure a long tool life. For this purpose, numerical simulations can be used to calculate the occurring stresses and the temperature development in the tools during the course of a stroke or over several forging cycles. The aim of this research is to investigate the effect of different radii on the resulting stresses in the lower die of the forming tools. Furthermore, the temperature evolution over several cycles is analysed to determine their effect on the temperature. When investigating the stress, it was found that a larger radius leads to a reduction in stresses. In addition, it could be numerically proven that the base temperature of the die levels off after a certain number of cycles. These findings will be used in further research dealing with the service life calculation of dies subjected to thermo-mechanical alternating stresses
Long-Term Effects of Serial Anodal tDCS on Motion Perception in Subjects with Occipital Stroke Measured in the Unaffected Visual Hemifield
Transcranial direct current stimulation (tDCS) is a novel neuromodulatory tool that has seen early transition to clinical trials, although the high variability of these findings necessitates further studies in clincally-relevant populations. The majority of evidence into effects of repeated tDCS is based on research in the human motor system, but it is unclear whether the long-term effects of serial tDCS are motor-specific or transferable to other brain areas. This study aimed to examine whether serial anodal tDCS over the visual cortex can exogenously induce long-term neuroplastic changes in the visual cortex. However, when the visual cortex is affected by a cortical lesion, up-regulated endogenous neuroplastic adaptation processes may alter the susceptibility to tDCS. To this end, motion perception was investigated in the unaffected hemifield of subjects with unilateral visual cortex lesions. Twelve subjects with occipital ischaemic lesions participated in a within-subject, sham-controlled, double-blind study. MRI-registered sham or anodal tDCS (1.5 mA, 20 minutes) was applied on five consecutive days over the visual cortex. Motion perception was tested before and after stimulation sessions and at 14- and 28-day follow-up. After a 16-day interval an identical study block with the other stimulation condition (anodal or sham tDCS) followed. Serial anodal tDCS over the visual cortex resulted in an improvement in motion perception, a function attributed to MT/V5. This effect was still measurable at 14- and 28-day follow-up measurements. Thus, this may represent evidence for long-term tDCS-induced plasticity and has implications for the design of studies examining the time course of tDCS effects in both the visual and motor systems
Subjective and objective assessment of physical activity in multiple sclerosis and their relation to health-related quality of life
Background Physical activity (PA) is frequently restricted in people with
multiple sclerosis (PwMS) and aiming to enhance PA is considered beneficial in
this population. We here aimed to explore two standard methods (subjective
plus objective) to assess PA reduction in PwMS and to describe the relation of
PA to health-related quality of life (hrQoL). Methods PA was objectively
measured over a 7-day period in 26 PwMS (EDSS 1.5–6.0) and 30 matched healthy
controls (HC) using SenseWear mini® armband (SWAmini) and reported as step
count, mean total and activity related energy expenditure (EE) as well as time
spent in PA of different intensities. Measures of EE were also derived from
self-assessment with IPAQ (International Physical Activity Questionnaire) long
version, which additionally yielded information on the context of PA and a
classification into subjects’ PA levels. To explore the convergence between
both types of assessment, IPAQ categories (low, moderate, high) were related
to selected PA parameters from objective assessment using ANOVA. Group
differences and associated effect sizes for all PA parameters as well as their
relation to clinical and hrQoL measures were determined. Results Both, SWAmini
and IPAQ assessment, captured differences in PA between PwMS and HC. IPAQ
categories fit well with common cut-offs for step count (p = 0.002) and mean
METs (p = 0.004) to determine PA levels with objective devices. Correlations
between specifically matched pairs of IPAQ and SWAmini parameters ranged
between r .288 and r .507. Concerning hrQoL, the lower limb mobility subscore
was related to four PA measures, while a relation with patients’ report of
general contentment was only seen for one. Conclusions Both methods of
assessment seem applicable in PwMS and able to describe reductions in daily PA
at group level. Whether they can be used to track individual effects of
interventions to enhance PA levels needs further exploration. The relation of
PA measures with hrQoL seen with lower limb mobility suggests lower limb
function not only as a major target for intervention to increase PA but also
as a possible surrogate for PA changes
7 Tesla MRI of Balo's concentric sclerosis versus multiple sclerosis lesions
Background: Baló’s concentric sclerosis (BCS) is a rare condition characterized by concentrically layered white matter lesions. While its pathogenesis is unknown, hypoxia-induced tissue injury and chemotactic stimuli have been proposed as potential causes of BCS lesion formation. BCS has been suggested to be a variant of multiple sclerosis (MS). Here, we aimed to elucidate similarities and differences between BCS and MS by describing lesion morphology and localization in high-resolution 7 Tesla (7 T) magnetic resonance imaging (MRI) scans. Methods: Ten patients with Baló-type lesions underwent 7 T MRI, and 10 relapsing remitting MS patients served as controls. The 7 T MR imaging protocol included 3D T1-weighted (T1w) magnetization-prepared rapid gradient echo, 2D high spatial resolution T2*-weighted (T2*w) fast low-angle shot and susceptibility-weighted imaging. Results: Intralesional veins were visible in the center of all but one Baló-type lesion. Four Baló-type lesions displayed inhomogeneous intralesional T2*w signal intensities, which are suggestive of microhemorrhages or small ectatic venules. Eight of 10 BCS patients presented with 97 additional lesions, 36 of which (37%) had a central vein. Lesions involving the cortical gray matter and the U-fibers were not detected in BCS patients. Conclusion: Our findings support the hypothesis that BCS and MS share common pathogenetic mechanisms but patients present with different lesion phenotypes
Analysis of Lymphocytic DNA Damage in Early Multiple Sclerosis by Automated Gamma-H2AX and 53BP1 Foci Detection: A Case Control Study
Background In response to DNA double-strand breaks, the histone protein H2AX
becomes phosphorylated at its C-terminal serine 139 residue, referred to as
γ-H2AX. Formation of γ-H2AX foci is associated with recruitment of p53-binding
protein 1 (53BP1), a regulator of the cellular response to DNA double-strand
breaks. γ-H2AX expression in peripheral blood mononuclear cells (PBMCs) was
recently proposed as a diagnostic and disease activity marker for multiple
sclerosis (MS). Objective To evaluate the significance of γ-H2AX and 53BP1
foci in PBMCs as diagnostic and disease activity markers in patients with
clinically isolated syndrome (CIS) and early relapsing-remitting MS (RRMS)
using automated γ-H2AX and 53BP1 foci detection. Methods Immunocytochemistry
was performed on freshly isolated PBMCs of patients with CIS/early RRMS (n =
25) and healthy controls (n = 27) with γ-H2AX and 53BP1 specific antibodies.
Nuclear γ-H2AX and 53BP1 foci were determined using a fully automated reading
system, assessing the numbers of γ-H2AX and 53BP1 foci per total number of
cells and the percentage of cells with foci. Patients underwent contrast
enhanced 3 Tesla magnetic resonance imaging (MRI) and clinical examination
including expanded disability status scale (EDSS) score. γ-H2AX and 53BP1 were
also compared in previously frozen PBMCs of each 10 CIS/early RRMS patients
with and without contrast enhancing lesions (CEL) and 10 healthy controls.
Results The median (range) number of γ-H2AX (0.04 [0–0.5]) and 53BP1 (0.005
[0–0.2]) foci per cell in freshly isolated PBMCs across all study participants
was low and similar to previously reported values of healthy individuals. For
both, γ-H2AX and 53BP1, the cellular focus number as well as the percentage of
positive cells did not differ between patients with CIS/RRMS and healthy
controls. γ-H2AX and 53BP1 levels neither correlated with number nor volume of
T2-weighted lesions on MRI, nor with the EDSS. Although γ-H2AX, but not 53BP1,
levels were higher in previously frozen PBMCs of patients with than without
CEL, γ-H2AX values of both groups overlapped and γ-H2AX did not correlate with
the number or volume of CEL. Conclusion γ-H2AX and 53BP1 foci do not seem to
be promising diagnostic or disease activity biomarkers in patients with early
MS. Lymphocytic DNA double-strand breaks are unlikely to play a major role in
the pathophysiology of MS
Detection of N-glycolyl-neuraminic acid-containing glycolipids in human skin
Humans lack the enzyme that produces the sialic acid N-glycolyl neuraminic acid (Neu5Gc), but several lines of evidence have shown that Neu5Gc can be taken up by mammalian food sources and replace the common human sialic acid N-acetyl neuraminic acid (Neu5Ac) in glycans. Cancer tissue has been shown to have increased the presence of Neu5Gc and Neu5Gc-containing glycolipids such as the ganglioside GM3, which have been proposed as tumor-specific antigens for antibody treatment. Here, we show that a previously described antibody against Neu5Gc-GM3 is binding to Neu5GC-containing gangliosides and is strongly staining different cancer tissues. However, we also found a strong intracellular staining of keratinocytes of healthy skin. We confirmed this staining on freshly isolated keratinocytes by flow cytometry and detected Neu5Gc by mass spectrometry. This finding implicates that non-human Neu5Gc can be incorporated into gangliosides in human skin, and this should be taken into consideration when targeting Neu5Gc-containing gangliosides for cancer immunotherapy
Structure-Guided Redesign Improves NFL HIV Env Trimer Integrity and Identifies an Inter-Protomer Disulfide Permitting Post-Expression Cleavage
Soluble HIV-1 envelope glycoprotein (Env) trimers are under active investigation as vaccine candidates in relevant pre-clinical models. Like SOSIPs, the cleavage-independent native flexibly linked (NFL) trimers are faithful mimics of the Env spike. Here, we analyzed multiple new designs to explore alternative modifications, informing tertiary interactions, while maintaining NFL trimer homogeneity and integrity. Accordingly, we performed a proline (P) substitution screen in the gp41 heptad repeat 1 region, identifying other trimer-enhancing Ps, including L555P. This P improved trimer integrity compared to I559P in selected properties. Next, we screened 15 structure-guided potential cysteine pairs in gp140 and found that A501C-L663C (“CC2”) forms an inter-protomer disulfide bond that demonstrably increased NFL trimer thermostability. We combined these two approaches with trimer-derived substitutions, coupled with glycine substitutions at helix-to-coil transitions, developed by our group. To increase the exposure of the fusion peptide (FP) N-terminus, we engineered an enterokinase (EK) cleavage site upstream of the FP for controlled post-expression cleavage. In combination, the redesigns resulted in highly stable and homogeneous NFL mimics derived from different clades. Following recombinant EK cleavage, the NFL trimers retained covalent linkage, maintaining a native-like structure while displaying enhanced stability and favorable antigenic features. These trimers also displayed increased exposure of neutralizing epitopes in the FP and gp120/gp41 interface, while retaining other neutralizing epitopes and occluding non-neutralizing elements. This array of Env-structure-guided designs reveals additional interactive regions in the prefusion state of the HIV Env spike, affording the development of novel antigens and immunogens
Improving the immunogenicity of native-like HIV-1 envelope trimers by hyperstabilization
The production of native-like recombinant versions of the HIV-1 envelope glycoprotein (Env) trimer requires overcoming the natural flexibility and instability of the complex. The engineered BG505 SOSIP.664 trimer mimics the structure and antigenicity of native Env. Here, we describe how the introduction of new disulfide bonds between the glycoprotein (gp)120 and gp41 subunits of SOSIP trimers of the BG505 and other genotypes improves their stability and antigenicity, reduces their conformational flexibility, and helps maintain them in the unliganded conformation. The resulting next-generation SOSIP.v5 trimers induce strong autologous tier-2 neutralizing antibody (NAb) responses in rabbits. In addition, the BG505 SOSIP.v6 trimers induced weak heterologous NAb responses against a subset of tier-2 viruses that were not elicited by the prototype BG505 SOSIP.664. These stabilization methods can be applied to trimers from multiple genotypes as components of multivalent vaccines aimed at inducing broadly NAbs (bNAbs)
MAPK pathway and B cells overactivation in multiple sclerosis revealed by phosphoproteomics and genomic analysis
Dysregulation of signaling pathways in multiple sclerosis (MS) can be analyzed by phosphoproteomics in peripheral blood mononuclear cells (PBMCs). We performed in vitro kinetic assays on PBMCs in 195 MS patients and 60 matched controls and quantified the phosphorylation of 17 kinases using xMAP assays. Phosphoprotein levels were tested for association with genetic susceptibility by typing 112 single-nucleotide polymorphisms (SNPs) associated with MS susceptibility. We found increased phosphorylation of MP2K1 in MS patients relative to the controls. Moreover, we identified one SNP located in the PHDGH gene and another on IRF8 gene that were associated with MP2K1 phosphorylation levels, providing a first clue on how this MS risk gene may act. The analyses in patients treated with disease-modifying drugs identified the phosphorylation of each receptor’s downstream kinases. Finally, using flow cytometry, we detected in MS patients increased STAT1, STAT3, TF65, and HSPB1 phosphorylation in CD19+ cells. These findings indicate the activation of cell survival and proliferation (MAPK), and proinflammatory (STAT) pathways in the immune cells of MS patients, primarily in B cells. The changes in the activation of these kinases suggest that these pathways may represent therapeutic targets for modulation by kinase inhibitors
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