scholarly journals Mixed-polarity random-dot stereograms alter GABA and Glx concentration in the early visual cortex

2019 ◽  
Author(s):  
Reuben Rideaux ◽  
Nuno Goncalves ◽  
Andrew E Welchman
Keyword(s):  
Visual Cortex ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Gaba Concentration ◽  
Recent Theoretical Work ◽  
Random Dot Stereograms ◽  
Mixed Polarity ◽  
Early Visual Cortex

ABSTRACTThe offset between images projected onto the left and right retinae (binocular disparity) provides a powerful cue to the three-dimensional structure of the environment. It was previously shown that depth judgements are better when images comprise both light and dark features, rather than only dark or only light elements. Since Harris and Parker (1995) discovered the “mixed-polarity benefit”, there has been limited evidence supporting their hypothesis that the benefit is due to separate bright and dark channels. Goncalves and Welchman (2017) observed that single- and mixed-polarity stereograms evoke different levels of positive and negative activity in a deep neural network trained on natural images to make depth judgements, which also showed the mixed-polarity benefit. Motivated by this discovery, here we seek to test the potential for changes in the balance of excitation and inhibition that are produced by viewing these stimuli. In particular, we use magnetic resonance spectroscopy to measure Glx and GABA concentration in the early visual cortex of adult humans while viewing single- and mixed-polarity random-dot stereograms (RDS). We find that observers’ Glx concentration is significantly higher while GABA concentration is significantly lower when viewing mixed-polarity RDS than when viewing single-polarity RDS. These results indicate that excitation and inhibition facilitate processing of single- and mixed-polarity stereograms in the early visual cortex to different extents, consistent with recent theoretical work (Goncalves & Welchman, 2017).

scholarly journals Mixed-polarity random-dot stereograms alter GABA and Glx concentration in the early visual cortex

2019 ◽  
Vol 122 (2) ◽  
pp. 888-896 ◽  
Author(s):  
Reuben Rideaux ◽  
Nuno R. Goncalves ◽  
Andrew E. Welchman
Keyword(s):  
Visual Cortex ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Gaba Concentration ◽  
Curr Biol ◽  
Random Dot Stereograms ◽  
Mixed Polarity ◽  
Early Visual Cortex

The offset between images projected onto the left and right retina (binocular disparity) provides a powerful cue to the three-dimensional structure of the environment. It was previously shown that depth judgements are better when images comprise both light and dark features, rather than only light or only dark elements. Since Harris and Parker ( Nature 374: 808–811, 1995) discovered the “mixed-polarity benefit,” there has been limited evidence supporting their hypothesis that the benefit is due to separate bright and dark channels. Goncalves and Welchman ( Curr Biol 27: 1403–1412, 2017) observed that single- and mixed-polarity stereograms evoke different levels of positive and negative activity in a deep neural network trained on natural images to make depth judgements, which also showed the mixed-polarity benefit. Motivated by this discovery, we seek to test the potential for changes in the balance of excitation and inhibition that are produced by viewing these stimuli. In particular, we use magnetic resonance spectroscopy to measure Glx and GABA concentrations in the early visual cortex of adult humans during viewing of single- and mixed-polarity random-dot stereograms (RDS). We find that participants’ Glx concentration is significantly higher, whereas GABA concentration is significantly lower, when mixed-polarity RDS are viewed than when single-polarity RDS are viewed. These results indicate that excitation and inhibition facilitate processing of single- and mixed-polarity stereograms in the early visual cortex to different extents, consistent with recent theoretical work (Goncalves NR, Welchman AE. Curr Biol 27: 1403–1412, 2017). NEW & NOTEWORTHY Depth judgements are better when images comprise both light and dark features, rather than only light or only dark elements. Using magnetic resonance spectroscopy, we show that adult human participants’ Glx concentration is significantly higher whereas GABA concentration is significantly lower in the early visual cortex when participants view mixed-polarity random-dot stereograms (RDS) compared with single-polarity RDS. These results indicate that excitation and inhibition facilitate processing of single- and mixed-polarity stereograms in the early visual cortex to different extents.

scholarly journals Structural characterization of a Thorarchaeota profilin indicates eukaryotic-like features but with an extended N-terminus

2021 ◽  
Author(s):  
Celestine N Chi ◽  
Ravi Teja Inturi ◽  
Sandra Martinez Lara ◽  
Mahmoud Darweesh
Keyword(s):  
Common Ancestor ◽  
Three Dimensional ◽  
Eukaryotic Cell ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Last Eukaryotic Common Ancestor ◽  
Rigid Core ◽  
N Terminus ◽  
Metagenomics Analysis

The emergence of the first eukaryotic cell was preceded by evolutionary events which are still highly debatable. Recently, comprehensive metagenomics analysis has uncovered that the Asgard super-phylum is the closest yet known archaea host of eukaryotes. However, it remains to be established if a large number of eukaryotic signature proteins predicated to be encoded by the Asgard super-phylum are functional at least, in the context of a eukaryotic cell. Here, we determined the three-dimensional structure of profilin from Thorarchaeota by nuclear magnetic resonance spectroscopy and show that this profilin has a rigid core with a flexible N-terminus which was previously implicated in polyproline binding. In addition, we also show that thorProfilin co-localizes with eukaryotic actin in cultured HeLa cells. This finding reaffirm the notion that Asgardean encoded proteins possess eukaryotic-like characteristics and strengthen likely existence of a complex cytoskeleton already in a last eukaryotic common ancestor

scholarly journals Characterization of the structure and redox behaviour of cytochrome c3 from Desulfovibrio baculatus by 1H-nuclear-magnetic-resonance spectroscopy

1993 ◽  
Vol 294 (3) ◽  
pp. 899-908 ◽  
Author(s):  
I B Coutinho ◽  
D L Turner ◽  
J LeGall ◽  
A V Xavier
Keyword(s):  
Chemical Shifts ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Cytochrome C3 ◽  
X Ray ◽  
1H Nuclear Magnetic Resonance ◽  
Proton Resonances ◽  
Nuclear Overhauser

Complete assignment of the aromatic and haem proton resonances in the cytochromes c3 isolated from Desulfovibrio baculatus strains (Norway 4, DSM 1741) and (DSM 1743) was achieved using one- and two-dimensional 1H n.m.r. Nuclear Overhauser enhancements observed between haem and aromatic resonances and between resonances due to different haems, together with the ring-current contributions to the chemical shifts of haem resonances, support the argument that the haem core architecture is conserved in the various cytochromes c3, and that the X-ray structure of the D. baculatus cytochrome c3 is erroneous. The relative orientation of the haems for both cytochromes was determined directly from n.m.r. data. The n.m.r. structures have a resolution of approximately 0.25 nm and are found to be in close agreement with the X-ray structure from D. vulgaris cytochrome c3. The proton assignments were used to relate the highest potential to a specific haem in the three-dimensional structure by monitoring the chemical-shift variation of several haem resonances throughout redox titrations followed by 1H n.m.r. The haem with highest redox potential is not the same as that in other cytochromes c3.

scholarly journals Amphotericin B Assembles into Seven-Molecule Ion Channels in Membrane Domain

2021 ◽  
Author(s):  
Yuichi Umegawa ◽  
Tomoya Yamamoto ◽  
Mayank Dixit ◽  
Kosuke Funahashi ◽  
Sangjae Seo ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Selective Toxicity ◽  
Drug Molecules ◽  
Conductive Channel ◽  
High Resolution Structure ◽  
Dynamics Simulations ◽  
Resolution Structure

Amphotericin B, a long-used antifungal drug, forms fungicidal ion-permeable channels across cell membranes. Using solid-state nuclear magnetic resonance spectroscopy and molecular dynamics simulations, we experimentally elucidated the three-dimensional structure of the molecular assemblies formed by this drug in membranes in the presence of the fungal sterol, ergosterol. A stable assembly of seven drug molecules was observed to form an ion conductive channel. The structure somewhat resembled the upper half of the barrel-stave model proposed in the 1970s but different substantially in the number of molecules and their arrangement. Based on the structure obtained, the aggregation of the channel assemblies in membranes was investigated and a mechanism was proposed in which complexation with ergosterol stabilizes the drug’s assemblies, leading to their aggregation, and in turn enhancing channel activity. The high-resolution structure is consistent with many previous findings, including structure-activity relationships of the drug, and the channel aggregation provides a more reasonable explanation for the selective toxicity of this drug to fungi.

scholarly journals Conformation of a Bactericidal Domain of Puroindoline a: Structure and Mechanism of Action of a 13-Residue Antimicrobial Peptide

2003 ◽  
Vol 185 (16) ◽  
pp. 4938-4947 ◽  
Author(s):  
Weiguo Jing ◽  
Alistair R. Demcoe ◽  
Hans J. Vogel
Keyword(s):  
Three Dimensional ◽  
Antimicrobial Activities ◽  
Specific Protein ◽  
Dimensional Structure ◽  
Phospholipid Vesicles ◽  
Resonance Spectroscopy ◽  
Membrane Interface ◽  
Bacterial Membranes ◽  
Rich Domain ◽  
Puroindoline A

ABSTRACT Puroindoline a, a wheat endosperm-specific protein containing a tryptophan-rich domain, was reported to have antimicrobial activities. We found that a 13-residue fragment of puroindoline a (FPVTWRWWKWWKG-NH2) (puroA) exhibits activity against both gram-positive and gram-negative bacteria. This suggests that puroA may be a bactericidal domain of puroindoline a. PuroA interacted strongly with negatively charged phospholipid vesicles and induced efficient dye release from these vesicles, suggesting that the microbicidal effect of puroA may be due to interactions with bacterial membranes. A variety of biophysical and biochemical methods, including fluorescence spectroscopy and microcalorimetry, were used to examine the mode of action of puroA. These studies showed that puroA is located at the membrane interface, probably due to its high content of Trp residues that have a high propensity to partition into the membrane interface. The penetration of these Trp residues in negatively charged phospholipid vesicles resembling bacterial membranes was more extensive than the penetration in neutral vesicles mimicking eukaryotic membranes. Peptide binding had a significant influence on the phase behavior of the former vesicles. The three-dimensional structure of micelle-bound puroA determined by two-dimensional nuclear magnetic resonance spectroscopy indicated that all the positively charged residues are oriented close to the face of Trp indole rings, forming energetically favorable cation-π interactions. This characteristic, along with its well-defined amphipathic structure upon binding to membrane mimetic systems, allows puroA to insert more deeply into bacterial membranes and disrupt the regular membrane bilayer structure.

scholarly journals Structural studies on the antimicrobial peptide Brevinin 1E by spectroscopic methods

2003 ◽  
Vol 17 (2-3) ◽  
pp. 127-138 ◽  
Author(s):  
Woo-Sung Son ◽  
Ji-Sun Kim ◽  
Hyung-Eun Kim ◽  
Sang-Ho Park ◽  
Bong-Jin Lee
Keyword(s):  
Antimicrobial Peptides ◽  
Antimicrobial Peptide ◽  
Three Dimensional ◽  
Helical Structure ◽  
Structural Motif ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Random Structure ◽  
Three Dimensional Structure ◽  
Pharmacologically Active

Skin extracts of frogs are a rich source of pharmacologically active peptides such as caeruleins, tachykinins, bradykinins, thyrotropin-releasing hormone, bombesin-like and opioid peptides. A large variety of antimicrobial peptides has been isolated fromRanaspecies. These peptides, grouped in several families on the basis of differing length and distinct activity, were found to have one structural motif in common: an intramolecular disulfide bridge located at the C-terminal end, forming a seven-member ring, which was designated ‘Rana box’. Brevinin 1E is a 24-residue antimicrobial peptide isolated from the skin of a frog,Rana brevipoda. This peptide shows a broad range of antimicrobial activity against prokaryotic cells but shows very much hemolytic activity against human red blood cells. The solution structure of Brevinin 1E was studied by using CD (circular dichroism) and NMR (nuclear magnetic resonance) spectroscopy. CD investigation revealed that Brevinin 1E adopts random structure in aqueous solution but adopts mainlyα-helical structure in TFE/water (6 : 4, v/v) solution. The three-dimensional structure of Brevinin 1E was determined in 60% TFE/water solution using homonuclear NMR spectroscopy. This peptide showed mainly anα-helical structure with amphipathic property. Its three-dimensional structure is similar to those of other peptides such as magainin, nigrocin and ranalexin. Therefore, Brevinin 1E can be classified into the family of antimicrobial peptides containing a single linearα-helix that interact with target microbial membrane, leading to cell death through disruption of membrane integrity.

Sign in / Sign up

Export Citation Format

Share Document