Artículos de revistas: "Altered tunings"

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Li, Wen-Wu, Timothy D. W. Claridge, Qiuhong Li, Mark R. Wormald, Benjamin G. Davis y Hagan Bayley. "Tuning the Cavity of Cyclodextrins: Altered Sugar Adaptors in Protein Pores". Journal of the American Chemical Society 133, n.º 6 (16 de febrero de 2011): 1987–2001. http://dx.doi.org/10.1021/ja1100867.

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Chen, Chia-Chin, Yikai Yin, Stephen Dongmin Kang, Wei Cai y William C. Chueh. "Electro-chemo-mechanical charge carrier equilibrium at interfaces". Physical Chemistry Chemical Physics 23, n.º 41 (2021): 23730–40. http://dx.doi.org/10.1039/d1cp02690a.

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Chen, Chia-Chin, Yikai Yin, Stephen Dongmin Kang, Wei Cai y William C. Chueh. "Electro-chemo-mechanical charge carrier equilibrium at interfaces". Physical Chemistry Chemical Physics 23, n.º 41 (2021): 23730–40. http://dx.doi.org/10.1039/d1cp02690a.

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Roh, Jinsook, Randall F. Beer, Andrew Lai, Monica Rho, Kristopher R. Karvelas, Antoun M. Nader, Mark C. Kendall y William Z. Rymer. "The Effects of Selective Muscle Weakness on Muscle Coordination in the Human Arm". Applied Bionics and Biomechanics 2018 (19 de septiembre de 2018): 1–16. http://dx.doi.org/10.1155/2018/5637568.

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Despite the fundamental importance of muscle coordination in daily life, it is currently unclear how muscle coordination adapts when the musculoskeletal system is perturbed. In this study, we quantified the impact of selective muscle weakness on several metrics of muscle coordination. Seven healthy subjects performed 2D and 3D isometric force target matches, while electromyographic (EMG) signals were recorded from 13 elbow and shoulder muscles. Subsequently, muscle weakness was induced by a motor point block of brachialis muscle. Postblock subjects repeated the force generation tasks. We quantified muscle coordination pre- and postblock using three metrics: tuning curve preferred direction, tuning curve area, and motor modules analysis via nonnegative matrix factorization. For most muscles, the tuning direction for the 2D protocol was not substantially altered postblock, while tuning areas changed more drastically. Typically, five motor modules were identified from the 3D task, and four motor modules were identified in the 2D task; this result held across both pre- and postblock conditions. The composition of one or two motor modules, ones that involved mainly the activation of shoulder muscles, was altered postblock. Our results demonstrate that selective muscle weakness can induce nonintuitive alternations in muscle coordination in the mechanically redundant human arm.

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Gold, Joshua I. y Eric I. Knudsen. "Hearing Impairment Induces Frequency-Specific Adjustments in Auditory Spatial Tuning in the Optic Tectum of Young Owls". Journal of Neurophysiology 82, n.º 5 (1 de noviembre de 1999): 2197–209. http://dx.doi.org/10.1152/jn.1999.82.5.2197.

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Bimodal, auditory-visual neurons in the optic tectum of the barn owl are sharply tuned for sound source location. The auditory receptive fields (RFs) of these neurons are restricted in space primarily as a consequence of their tuning for interaural time differences and interaural level differences across broad ranges of frequencies. In this study, we examined the extent to which frequency-specific features of early auditory experience shape the auditory spatial tuning of these neurons. We manipulated auditory experience by implanting in one ear canal an acoustic filtering device that altered the timing and level of sound reaching the eardrum in a frequency-dependent fashion. We assessed the auditory spatial tuning at individual tectal sites in normal owls and in owls raised with the filtering device. At each site, we measured a family of auditory RFs using broadband sound and narrowband sounds with different center frequencies both with and without the device in place. In normal owls, the narrowband RFs for a given site all included a common region of space that corresponded with the broadband RF and aligned with the site's visual RF. Acute insertion of the filtering device in normal owls shifted the locations of the narrowband RFs away from the visual RF, the magnitude and direction of the shifts depending on the frequency of the stimulus. In contrast, in owls that were raised wearing the device, narrowband and broadband RFs were aligned with visual RFs so long as the device was in the ear but not after it was removed, indicating that auditory spatial tuning had been adaptively altered by experience with the device. The frequency tuning of tectal neurons in device-reared owls was also altered from normal. The results demonstrate that experience during development adaptively modifies the representation of auditory space in the barn owl's optic tectum in a frequency-dependent manner.

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Duru, Adil Doganay, Renhua Sun, Eva B. Allerbring, Jesseka Chadderton, Nadir Kadri, Xiao Han, Kaliroi Peqini et al. "Tuning antiviral CD8 T-cell response via proline-altered peptide ligand vaccination". PLOS Pathogens 16, n.º 5 (4 de mayo de 2020): e1008244. http://dx.doi.org/10.1371/journal.ppat.1008244.

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Rauch, Steven D., Guangwei Zhou, Sharon G. Kujawa, John J. Guinan y Barbara S. Herrmann. "Vestibular Evoked Myogenic Potentials Show Altered Tuning in Patients with Ménière’s Disease". Otology & Neurotology 25, n.º 3 (mayo de 2004): 333–38. http://dx.doi.org/10.1097/00129492-200405000-00022.

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Lin, Jian-Xin y Warren J. Leonard. "Fine-Tuning Cytokine Signals". Annual Review of Immunology 37, n.º 1 (26 de abril de 2019): 295–324. http://dx.doi.org/10.1146/annurev-immunol-042718-041447.

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Cytokines are secreted or otherwise released polypeptide factors that exert autocrine and/or paracrine actions, with most cytokines acting in the immune and/or hematopoietic system. They are typically pleiotropic, controlling development, cell growth, survival, and/or differentiation. Correspondingly, cytokines are clinically important, and augmenting or attenuating cytokine signals can have deleterious or therapeutic effects. Besides physiological fine-tuning of cytokine signals, altering the nature or potency of the signal can be important in pathophysiological responses and can also provide novel therapeutic approaches. Here, we give an overview of cytokines, their signaling and actions, and the physiological mechanisms and pharmacologic strategies to fine-tune their actions. In particular, the differential utilization of STAT proteins by a single cytokine or by different cytokines and STAT dimerization versus tetramerization are physiological mechanisms of fine-tuning, whereas anticytokine and anticytokine receptor antibodies and cytokines with altered activities, including cytokine superagonists, partial agonists, and antagonists, represent new ways of fine-tuning cytokine signals.

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Ho, Tracey T. M., Kristen E. Bremmell, Marta Krasowska, Damien N. Stringer, Benjamin Thierry y David A. Beattie. "Tuning polyelectrolyte multilayer structure by exploiting natural variation in fucoidan chemistry". Soft Matter 11, n.º 11 (2015): 2110–24. http://dx.doi.org/10.1039/c4sm02552k.

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Polyelectrolyte multilayers of fucoidan with chitosan have film characteristics that depend on the species of seaweed from which the fucoidan is extracted. Acetylation of the fucoidan (and altered molecular weight) is implicated in the formation of denser, less hydrated multilayers.

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Saul, A. B. y M. S. Cynader. "Adaptation in single units in visual cortex: The tuning of aftereffects in the spatial domain". Visual Neuroscience 2, n.º 6 (junio de 1989): 593–607. http://dx.doi.org/10.1017/s0952523800003527.

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AbstractCat striate cortical neurons were investigated using a new method of studying adaptation aftereffects. Stimuli were sinusoidal gratings of variable contrast, spatial frequency, and drift direction and rate. A series of alternating adapting and test trials was presented while recording from single units. Control trials were completely integrated with the adapted trials in these experiments.Every cortical cell tested showed selective adaptation aftereffects. Adapting at suprathreshold contrasts invariably reduced contrast sensitivity. Significant aftereffects could be observed even when adapting at low contrasts.The spatial-frequency tuning of aftereffects varied from cell to cell. Adapting at a given spatial frequency generally resulted in a broad response reduction at test frequencies above and below the adapting frequency. Many cells lost responses predominantly at frequencies lower than the adapting frequency.The tuning of aftereffects varied with the adapting frequency. In particular, the strongest aftereffects occurred near the adapting frequency. Adapting at frequencies just above the optimum for a cell often altered the spatial-frequency tuning by shifting the peak toward lower frequencies. The fact that the tuning of aftereffects did not simply match the tuning of the cell, but depended on the adapting stimulus, implies that extrinsic mechanisms are involved in adaptation effects.

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Jing, Zhixin y David Fooksman. "Altered Cellular Dynamics and Surface Expression Promote Long-Lived Plasma Cell Survival". Blood 142, Supplement 1 (28 de noviembre de 2023): 5386. http://dx.doi.org/10.1182/blood-2023-186540.

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Serological memory following vaccination decline with aging, indicating reduced survival of new plasma cells (PCs). We report that with age, bone marrow (BM) PC pool is enriched in long-lived plasma cells (LLPCs), leading to reduced PC turnover, suggesting increased competition. Using in vivo imaging, we find that LLPCs are highly organized into April-dependent clusters. Based on bulk RNA sequencing, and flow-based surface phenotyping, LLPCs exhibit unique transcriptome and proteome, fine tuning expression of key cell surface molecules, including CD93, CD81, CXCR4, CD326, CD44 and CD48, important for adhesion and homing. To test their functional role, Cxcr4 was conditionally deleted in PCs following immunization, which led to rapid mobilization from the BM, reduced survival of antigen-specific PCs, and accelerated decay of antibody titer. Analysis of endogenous LLPCs BCR repertoire exhibits reduced diversity, reduced somatic mutations, and increased public clones and IgM isotypes, particularly in young mice, suggesting non-random selection into the LLPC pool that is age-dependent.

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Cucić, Vuk. "Fine tuning of the General administrative procedure act". Anali Pravnog fakulteta u Beogradu, n.º 2/2018 (14 de julio de 2018): 139–63. http://dx.doi.org/10.51204/anali_pfub_18206a.

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General Administrative Procedure Act was enacted in 2016 and started to be applied as of June 1, 2017. The new law brought important novelties and significantly altered the concept of its predecessor, which has tradition longer than eight decades. As it suits the law of such prominence and the scope and importance of the novelties, the new General Administrative Procedure Act provoked contrasting reactions in the academic community – from critique to commendations. The author of the paper (at the same time the one of the authors of the draft law) proposes amendments to the law that could ameliorate the administrative procedure. The author of the paper finds that there is a space for improvement of the provisions concerning the guarantee act, parties, delivery, objection, appeal and enforcement procedure.

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Stevenson, Ian H., Anil Cherian, Brian M. London, Nicholas A. Sachs, Eric Lindberg, Jacob Reimer, Marc W. Slutzky, Nicholas G. Hatsopoulos, Lee E. Miller y Konrad P. Kording. "Statistical assessment of the stability of neural movement representations". Journal of Neurophysiology 106, n.º 2 (agosto de 2011): 764–74. http://dx.doi.org/10.1152/jn.00626.2010.

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In systems neuroscience, neural activity that represents movements or sensory stimuli is often characterized by spatial tuning curves that may change in response to training, attention, altered mechanics, or the passage of time. A vital step in determining whether tuning curves change is accounting for estimation uncertainty due to measurement noise. In this study, we address the issue of tuning curve stability using methods that take uncertainty directly into account. We analyze data recorded from neurons in primary motor cortex using chronically implanted, multielectrode arrays in four monkeys performing center-out reaching. With the use of simulations, we demonstrate that under typical experimental conditions, the effect of neuronal noise on estimated preferred direction can be quite large and is affected by both the amount of data and the modulation depth of the neurons. In experimental data, we find that after taking uncertainty into account using bootstrapping techniques, the majority of neurons appears to be very stable on a timescale of minutes to hours. Lastly, we introduce adaptive filtering methods to explicitly model dynamic tuning curves. In contrast to several previous findings suggesting that tuning curves may be in constant flux, we conclude that the neural representation of limb movement is, on average, quite stable and that impressions to the contrary may be largely the result of measurement noise.

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Pinkhasov, Julia, Jan Lee, LiQi Li, Dalal El-khoury, Renaud Lesourne, SuJin Hwang, Yongqing Zhang, Nan Ping Weng y Paul Love. "Identifying molecules that “fine-tune” T cell antigen receptor signaling during thymocyte selection. (36.40)". Journal of Immunology 184, n.º 1_Supplement (1 de abril de 2010): 36.40. http://dx.doi.org/10.4049/jimmunol.184.supp.36.40.

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Abstract The prevailing view of thymocyte selection is that the fate of developing cells is dictated exclusively by the affinity/avidity of the expressed TCR for self-MHC/self-ligand. We hypothesize that there is significant plasticity in the signaling processes that control T cell development and that the ability to ‘fine-tune’ the TCR signaling response, through the regulated expression of molecules that positively or negatively impact the TCR signaling response operates to maximize the TCR repertoire. One example of a ‘fine-tuning’ molecule that was previously characterized is the cell surface protein CD5. We found that CD5 is an inhibitory tuning receptor, and its surface expression is directly and proportionately regulated by the affinity of the TCR for selecting ligand. In order to identify additional candidates for ‘TCR-tuning’, we employed a TCR transgenic experimental system where TCR expression was fixed on all developing thymocytes and where the affinity of the positively selecting TCR/self-MHC/self-ligand interaction could be altered by changing the MHC haplotype. Thymocytes that successfully underwent selection under conditions of relatively low or relatively high avidity interactions were analyzed by microarray. These experiments identified CD5 as well as several additional potential tuning molecules not previously thought to play a role in ‘TCR-tuning’. Our results provide important new insights into the genetic and molecular processes that control thymocyte selection.

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Pinkhasov, Julia, Jan Lee, Dalal El-Khoury, LiQi Lee, SuJin Hwang, Renaud Lesourne, Yongqing Zhang, Nan-Ping Weng y Paul Love. "Identifying molecules that “fine-tune” T cell antigen receptor signaling during thymocyte selection. (64.5)". Journal of Immunology 186, n.º 1_Supplement (1 de abril de 2011): 64.5. http://dx.doi.org/10.4049/jimmunol.186.supp.64.5.

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Abstract The prevailing view of thymocyte selection is that the fate of developing cells is dictated exclusively by the affinity/avidity of the expressed TCR for self-MHC/self-ligand. We hypothesize that there is significant plasticity in the signaling processes that control T cell development and that the ability to ‘fine-tune’ the TCR signaling response, through the regulated expression of molecules that positively or negatively impact the TCR signaling response operates to maximize the TCR repertoire. One example of a ‘fine-tuning’ molecule that was previously characterized is the cell surface protein CD5. We found that CD5 is an inhibitory tuning receptor, and its surface expression is directly and proportionately regulated by the affinity of the TCR for selecting ligand. In order to identify additional candidates for ‘TCR-tuning’, we employed a TCR transgenic experimental system where TCR expression was fixed on all developing thymocytes and where the affinity of the positively selecting TCR/self-MHC/self-ligand interaction could be altered by changing the MHC haplotype. Thymocytes that successfully underwent selection under conditions of relatively low or relatively high avidity interactions were analyzed by microarray. These experiments identified CD5 as well as several additional potential tuning molecules not previously thought to play a role in ‘TCR-tuning’. Our results provide important new insights into the genetic and molecular processes that control thymocyte selection.

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16

Ganeshraja, Ayyakannu Sundaram, Kanniah Rajkumar, Kaixin Zhu, Xuning Li, Subramani Thirumurugan, Wei Xu, Jing Zhang, Minghui Yang, Krishnamoorthy Anbalagan y Junhu Wang. "Facile synthesis of iron oxide coupled and doped titania nanocomposites: tuning of physicochemical and photocatalytic properties". RSC Advances 6, n.º 76 (2016): 72791–802. http://dx.doi.org/10.1039/c6ra13212j.

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The iron oxide coupled and doped titania nanocomposites exhibited altered compositional, optical, electrical, magnetic and photocatalytic properties with respect to varying dosage of iron in the titania matrix.

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Brand, Antje, Reas Urban y Benedikt Grothe. "Duration Tuning in the Mouse Auditory Midbrain". Journal of Neurophysiology 84, n.º 4 (1 de octubre de 2000): 1790–99. http://dx.doi.org/10.1152/jn.2000.84.4.1790.

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Temporal cues, including sound duration, are important for sound identification. Neurons tuned to the duration of pure tones were first discovered in the auditory system of frogs and bats and were discussed as specific adaptations in these animals. More recently duration sensitivity has also been described in the chinchilla midbrain and the cat auditory cortex, indicating that it might be a more general phenomenon than previously thought. However, it is unclear whether duration tuning in mammals is robust in face of changes of stimulus parameters other than duration. Using extracellular single-cell recordings in the mouse inferior colliculus, we found 55% of cells to be sensitive to stimulus duration showing long-pass, short-pass, or band-pass filter characteristics. For most neurons, a change in some other stimulus parameter, (e.g., intensity, frequency, binaural conditions, or using noise instead of pure tones) altered and sometimes abolished duration-tuning characteristics. Thus in many neurons duration tuning is interdependent with other stimulus parameters and, hence, might be context dependent. A small number of inferior colliculus neurons, in particular band-pass neurons, exhibited stable filter characteristics and could therefore be referred to as “duration selective.” These findings support the idea that duration tuning is a general phenomenon in the mammalian auditory system.

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Hillenbrand, Ulrich y J. Leo van Hemmen. "Adaptation in the corticothalamic loop: computational prospects of tuning the senses". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 357, n.º 1428 (29 de diciembre de 2002): 1859–67. http://dx.doi.org/10.1098/rstb.2002.1174.

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The present article discusses computational hypotheses on corticothalamic feedback and modulation of cortical response properties. We have recently proposed that the two phenomena are related, hypothesizing that neuronal velocity preference in the visual cortex is altered by feedback to the lateral geniculate nucleus. We now contrast the common view that response adaptation to stimuli subserves a function of redundancy reduction with the idea that it may enhance cortical representation of objects. Our arguments lead to the concept that the corticothalamic loop is involved in reducing sensory input to behaviourally relevant aspects, a pre–attentive gating.

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Liu, Fang, John Hollis Rice, Valeria Lopes, Parwinder Grewal, Sarah L. Lebeis, Tarek Hewezi y Margaret E. Staton. "Overexpression of Strigolactone-Associated Genes Exerts Fine-Tuning Selection on Soybean Rhizosphere Bacterial and Fungal Microbiome". Phytobiomes Journal 4, n.º 3 (enero de 2020): 239–51. http://dx.doi.org/10.1094/pbiomes-01-20-0003-r.

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Strigolactones are a recently discovered class of carotenoid-derived plant hormones with a wide variety of functions, including acting as signaling molecules in the rhizosphere to promote arbuscular mycorrhizal fungi colonization and parasitic seed germination. To determine whether strigolactones influence the recruitment of microbes to the rhizosphere, we characterized both bacterial and fungal communities in response to the overexpression of genes involved in strigolactone biosynthesis (MAX1d) and signaling perception (D14 and MAX2a) in soybean (Glycine max). The amplicon sequencing-based results suggest that strigolactone overexpression lines had altered soybean rhizosphere bacteria composition at both the community level and individual taxa level with genera including Shinella and Bdellovibrio consistently more abundant across all three overexpression constructs. In addition, the responses of the soybean rhizosphere bacteria community differed significantly across the genes, with lines overexpressing genes involved in strigolactone biosynthesis (MAX1d) yielding a divergent bacterial community in comparison with those with altered expression of strigolactone perception genes (D14 and MAX2a). The overexpressed genes did not significantly impact the overall fungal community distribution; however, some individual taxa were altered in abundance. MAX1d and D14 overexpression lines had significantly enriched abundance of Fusarium solani. The mediating role of strigolactone biosynthesis and signaling genes on soybean rhizosphere bacterial and fungal communities confirmed strigolactone’s importance in the rhizosphere host–microbe communication and microbial community structure. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

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Heider, Barbara, Anushree Karnik, Nirmala Ramalingam y Ralph M. Siegel. "Neural Representation During Visually Guided Reaching in Macaque Posterior Parietal Cortex". Journal of Neurophysiology 104, n.º 6 (diciembre de 2010): 3494–509. http://dx.doi.org/10.1152/jn.01050.2009.

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Visually guided hand movements in primates require an interconnected network of various cortical areas. Single unit firing rate from area 7a and dorsal prelunate (DP) neurons of macaque posterior parietal cortex (PPC) was recorded during reaching movements to targets at variable locations and under different eye position conditions. In the eye position–varied task, the reach target was always foveated; thus eye position varied with reach target location. In the retinal-varied task, the monkey reached to targets at variable retinotopic locations while eye position was kept constant in the center. Spatial tuning was examined with respect to temporal (task epoch) and contextual (task condition) aspects, and response fields were compared. The analysis showed distinct tuning types. The majority of neurons changed their gain field tuning and retinotopic tuning between different phases of the task. Between the onset of visual stimulation and the preparatory phase (before the go signal), about one half the neurons altered their firing rate significantly. Spatial response fields during preparation and initiation epochs were strongly influenced by the task condition (eye position varied vs. retinal varied), supporting a strong role of eye position during visually guided reaching. DP neurons, classically considered visual, showed reach related modulation similar to 7a neurons. This study shows that both area 7a and DP are modulated during reaching behavior in primates. The various tuning types in both areas suggest distinct populations recruiting different circuits during visually guided reaching.

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Brown, Thomas C. y Aaron W. McGee. "Monocular deprivation during the critical period alters neuronal tuning and the composition of visual circuitry". PLOS Biology 21, n.º 4 (21 de abril de 2023): e3002096. http://dx.doi.org/10.1371/journal.pbio.3002096.

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Abnormal visual experience during a developmental critical period degrades cortical responsiveness. Yet how experience-dependent plasticity alters the response properties of individual neurons and composition of visual circuitry is unclear. Here, we measured with calcium imaging in alert mice how monocular deprivation (MD) during the developmental critical period affects tuning for binocularity, orientation, and spatial frequency for neurons in primary visual cortex. MD of the contralateral eye did not uniformly shift ocular dominance (OD) of neurons towards the fellow ipsilateral eye but reduced the number of monocular contralateral neurons and increased the number of monocular ipsilateral neurons. MD also impaired matching of preferred orientation for binocular neurons and reduced the percentage of neurons responsive at most spatial frequencies for the deprived contralateral eye. Tracking the tuning properties for several hundred neurons before and after MD revealed that the shift in OD is complex and dynamic, with many previously monocular neurons becoming binocular and binocular neurons becoming monocular. Binocular neurons that became monocular were more likely to lose responsiveness to the deprived contralateral eye if they were better matched for orientation prior to deprivation. In addition, the composition of visual circuitry changed as population of neurons more responsive to the deprived eye were exchanged for neurons with tuning properties more similar to the network of responsive neurons altered by MD. Thus, plasticity during the critical period adapts to recent experience by both altering the tuning of responsive neurons and recruiting neurons with matching tuning properties.

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Smith, Jennifer Anne, Jared Balolong, Nijun Jin, Caroline Whitty, John W. Kappler y Mark S. Anderson. "Tuning peptide specificity for T cell tolerance in Type 1 diabetes". Journal of Immunology 210, n.º 1_Supplement (1 de mayo de 2023): 78.09. http://dx.doi.org/10.4049/jimmunol.210.supp.78.09.

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Abstract Type 1 Diabetes (T1D) is a classical T-cell mediated autoimmune disease, and fundamental data have implicated insulin as the dominant autoantigen in T1D disease. In the NOD mouse model of T1D, notable studies have found that mice lacking native insulin expression but with an altered insulin sequence to maintain blood glucose levels are protected from insulitis and diabetes. Growing evidence also indicates how the insulin peptide is bound within MHC Class II (peptide register) is essential in determining the strength of interactions and recognition of autoreactive T-cells. We have uncovered a unique peptide binding characterized by the dominant insulin epitope InsB:9–23. The majority of InsB:9–23-specific CD4 T-cells in the periphery recognize insulin bound in the unusual register 3, and knocking in this single amino acid variation into just one copy of the insulin gene in NOD mice, confers protection against T1D. In addition, these mice were protected from T1D, even when treated with checkpoint inhibitor blockade, unlike their wild-type littermates. Introducing this superagonist epitope into the NOD mouse has allowed us to address several key questions surrounding pathways of peptide generation, presentation by MHC molecules, and recognition by auto-reactive pathogenic T cells. In addition, we have been able to model how central and peripheral tolerance mechanisms can be altered when major epitopes in the Insulin gene are mutated, allowing us to explore means of dominant tolerance to understand the potential for translation into treatments for T1D. Supported by grants from NIH (R01 DK133443-01A)

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Perich, Matthew G. y Lee E. Miller. "Altered tuning in primary motor cortex does not account for behavioral adaptation during force field learning". Experimental Brain Research 235, n.º 9 (6 de junio de 2017): 2689–704. http://dx.doi.org/10.1007/s00221-017-4997-1.

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Guimarães, José R., Diego Carballares, Paulo W. Tardioli, Javier Rocha-Martin y Roberto Fernandez-Lafuente. "Tuning Immobilized Commercial Lipase Preparations Features by Simple Treatment with Metallic Phosphate Salts". Molecules 27, n.º 14 (13 de julio de 2022): 4486. http://dx.doi.org/10.3390/molecules27144486.

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Four commercial immobilized lipases biocatalysts have been submitted to modifications with different metal (zinc, cobalt or copper) phosphates to check the effects of this modification on enzyme features. The lipase preparations were Lipozyme®TL (TLL-IM) (lipase from Thermomyces lanuginose), Lipozyme®435 (L435) (lipase B from Candida antarctica), Lipozyme®RM (RML-IM), and LipuraSelect (LS-IM) (both from lipase from Rhizomucor miehei). The modifications greatly altered enzyme specificity, increasing the activity versus some substrates (e.g., TLL-IM modified with zinc phosphate in hydrolysis of triacetin) while decreasing the activity versus other substrates (the same preparation in activity versus R- or S- methyl mandelate). Enantiospecificity was also drastically altered after these modifications, e.g., LS-IM increased the activity versus the R isomer while decreasing the activity versus the S isomer when treated with copper phosphate. Regarding the enzyme stability, it was significantly improved using octyl-agarose-lipases. Using all these commercial biocatalysts, no significant positive effects were found; in fact, a decrease in enzyme stability was usually detected. The results point towards the possibility of a battery of biocatalysts, including many different metal phosphates and immobilization protocols, being a good opportunity to tune enzyme features, increasing the possibilities of having biocatalysts that may be suitable for a specific process.

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Angelaki, D. E. y B. J. Hess. "Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. II Spatiotemporal properties of the adapted slow-phase eye velocity". Journal of Neurophysiology 76, n.º 5 (1 de noviembre de 1996): 2954–71. http://dx.doi.org/10.1152/jn.1996.76.5.2954.

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1. The ability of the vestibuloocular reflex (VOR) to undergo adaptive modification after selective changes in the peripheral vestibular system was investigated in rhesus monkeys by recording three-dimensional eye movements before and after inactivation of selective semicircular canals. In the preceding paper we showed that the horizontal VOR gain evoked by passive yaw oscillations after lateral semicircular canal inactivation recovers gradually over time in a frequency-specific manner. Here we present the spatial tuning of the adapted slow-phase eye velocity and describe its spatiotemporal properties as a function of time after canal inactivation. 2. The spatial organization of the VOR was investigated during oscillations at different head positions in the pitch, roll, and yaw planes, as well as in the right anterior/left posterior and left anterior/right posterior canal planes. Acutely after bilateral inactivation of the lateral semicircular canals, a small horizontal response could still be elicited that peaked during rotations in pitched head positions that would maximally stimulate vertical semicircular canals. In addition, the phase of horizontal slow-phase velocity abruptly reversed through 180 degrees at positions close to upright, similarly to torsional slow-phase velocity. These spatial response properties suggest that the small, residual horizontal response components that are present acutely after plugging of both lateral canals originate from vertical semicircular canal signals. 3. As the horizontal response amplitude increased over time, consistent changes were also observed in the spatiotemporal tuning of horizontal slow-phase velocity. 1) The spatiotemporal response properties of horizontal slow-phase velocity acquired noncosine tuning characteristics, primarily in the pitch plane, in the right anterior/left posterior and left anterior/right posterior canal planes. Accordingly, horizontal response amplitude was nonzero during rotation in any head position in these planes and response phase varied significantly as a function of head orientation. 2) The peak horizontal response amplitude shifted spatially over time, such that 5–10 mo after plugging it was maximal during rotations at head positions close to upright. 4. In parallel to these unique spatiotemporal response properties characterizing the adapted horizontal VOR, torsional slow-phase velocity also exhibited small spatiotemporal changes after lateral canal inactivation that tended to precede in time the changes associated with the horizontal response components. In contrast, vertical slow-phase velocity in the plugged animals was unaltered and continued to be characterized by cosine-tuned spatial properties in three dimensions. 5. Recovery of the horizontal response gain during yaw oscillations in upright position, as well as the unique, noncosine spatiotemporal characteristics of the adapted horizontal VOR, were also observed in an animal with all but one vertical semicircular canals inactivated. There was, however, no sign of VOR gain recovery up to 2 mo after all semicircular canals were inactivated. These results suggest that the observed recovery of horizontal VOR is at least partly due to signals originating from the remaining intact vertical canal(s). Even in the presence of a single intact vertical canal, the improvement in horizontal gaze stability is at least partly restored through spatiotemporal changes in the processing of vestibuloocular signals that improve the gain and spatial tuning of horizontal VOR at the expense of temporal response properties.

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Segers, Lauren S., Sarah C. Nuding, Mackenzie M. Ott, Russell O’Connor, Kendall F. Morris y Bruce G. Lindsey. "Blood pressure drives multispectral tuning of inspiration via a linked-loop neural network". Journal of Neurophysiology 124, n.º 6 (1 de diciembre de 2020): 1676–97. http://dx.doi.org/10.1152/jn.00442.2020.

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The brain network that supports cardiorespiratory coupling remains poorly understood. Using multielectrode arrays, we tested the hypothesis that blood pressure and baroreceptor reflexes “tune” the breathing motor pattern via a raphe-pontomedullary network. Neuron responses to changes in arterial pressure and identified functional connectivity, together with altered high frequency and slow Lundberg B-wave oscillations, support a model with linked recurrent inhibitory loops that stabilize the respiratory network and provide a path for transmission of baroreceptor signals.

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27

Hönes, Georg Sebastian, Nina Härting, Jens Mittag y Frank J. Kaiser. "TRα2—An Untuned Second Fiddle or Fine-Tuning Thyroid Hormone Action?" International Journal of Molecular Sciences 23, n.º 13 (23 de junio de 2022): 6998. http://dx.doi.org/10.3390/ijms23136998.

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Thyroid hormones (THs) control a wide range of physiological functions essential for metabolism, growth, and differentiation. On a molecular level, TH action is exerted by nuclear receptors (TRs), which function as ligand-dependent transcription factors. Among several TR isoforms, the function of TRα2 remains poorly understood as it is a splice variant of TRα with an altered C-terminus that is unable to bind T3. This review highlights the molecular characteristics of TRα2, proposed mechanisms that regulate alternative splicing and indications pointing towards an antagonistic function of this TR isoform in vitro and in vivo. Moreover, remaining knowledge gaps and major challenges that complicate TRα2 characterization, as well as future strategies to fully uncover its physiological relevance, are discussed.

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28

Verma, Archana, John P. Stoppelman y Jesse G. McDaniel. "Tuning Water Networks via Ionic Liquid/Water Mixtures". International Journal of Molecular Sciences 21, n.º 2 (8 de enero de 2020): 403. http://dx.doi.org/10.3390/ijms21020403.

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Water in nanoconfinement is ubiquitous in biological systems and membrane materials, with altered properties that significantly influence the surrounding system. In this work, we show how ionic liquid (IL)/water mixtures can be tuned to create water environments that resemble nanoconfined systems. We utilize molecular dynamics simulations employing ab initio force fields to extensively characterize the water structure within five different IL/water mixtures: [BMIM + ][BF 4 − ], [BMIM + ][PF 6 − ], [BMIM + ][OTf − ], [BMIM + ][NO 3 − ] and [BMIM + ][TFSI − ] ILs at varying water fraction. We characterize water clustering, hydrogen bonding, water orientation, pairwise correlation functions and percolation networks as a function of water content and IL type. The nature of the water nanostructure is significantly tuned by changing the hydrophobicity of the IL and sensitively depends on water content. In hydrophobic ILs such as [BMIM + ][PF 6 − ], significant water clustering leads to dynamic formation of water pockets that can appear similar to those formed within reverse micelles. Furthermore, rotational relaxation times of water molecules in supersaturated hydrophobic IL/water mixtures indicate the close-connection with nanoconfined systems, as they are quantitatively similar to water relaxation in previously characterized lyotropic liquid crystals. We expect that this physical insight will lead to better design principles for incorporation of ILs into membrane materials to tune water nanostructure.

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29

Zhang, Shuai, Yuan Hou, Suzhi Li, Luqi Liu, Zhong Zhang, Xi-Qiao Feng y Qunyang Li. "Tuning friction to a superlubric state via in-plane straining". Proceedings of the National Academy of Sciences 116, n.º 49 (28 de octubre de 2019): 24452–56. http://dx.doi.org/10.1073/pnas.1907947116.

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Controlling, and in many cases minimizing, friction is a goal that has long been pursued in history. From the classic Amontons–Coulomb law to the recent nanoscale experiments, the steady-state friction is found to be an inherent property of a sliding interface, which typically cannot be altered on demand. In this work, we show that the friction on a graphene sheet can be tuned reversibly by simple mechanical straining. In particular, by applying a tensile strain (up to 0.60%), we are able to achieve a superlubric state (coefficient of friction nearly 0.001) on a suspended graphene. Our atomistic simulations together with atomically resolved friction images reveal that the in-plane strain effectively modulates the flexibility of graphene. Consequently, the local pinning capability of the contact interface is changed, resulting in the unusual strain-dependent frictional behavior. This work demonstrates that the deformability of atomic-scale structures can provide an additional channel of regulating the friction of contact interfaces involving configurationally flexible materials.

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30

Wong, Phillip, Gregory M. Barton, Katherine A. Forbush y Alexander Y. Rudensky. "Dynamic Tuning of T Cell Reactivity by Self-Peptide–Major Histocompatibility Complex Ligands". Journal of Experimental Medicine 193, n.º 10 (21 de mayo de 2001): 1179–88. http://dx.doi.org/10.1084/jem.193.10.1179.

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Intrathymic self-peptide–major histocompatibility complex class II (MHC) molecules shape the T cell repertoire through positive and negative selection of immature CD4+CD8+ thymocytes. By analyzing the development of MHC class II–restricted T cell receptor (TCR) transgenic T cells under conditions in which the endogenous peptide repertoire is altered, we show that self-peptide–MHC complexes are also involved in setting T cell activation thresholds. This occurs through changes in the expression level of molecules on thymocytes that influence the sensitivity of TCR signaling. Our results suggest that the endogenous peptide repertoire modulates T cell responsiveness in the thymus in order to enforce tolerance to self-antigens.

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31

Thowladda, W. y S. T. Khlayboonme. "Plasma Impedance Tuning Effect on Nanostructure of Diamond Films". Applied Mechanics and Materials 394 (septiembre de 2013): 32–37. http://dx.doi.org/10.4028/www.scientific.net/amm.394.32.

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The morphology and structure of nanocrystalline diamond films as well as the plasma chemistry were studied by altering the plasma impedance. These impedances related to electron density were altered via the matching system. Two films were grown by the microwave plasma under different values of the plasma impedance, resulting in low and high electron densities in the plasma. By the use of measurements of plasma impedance and optical emission, the lowering of an inductive component of the impedance, indicating an increasing electron density, encouraged H-radical concentration present in the plasma. As the plasma was changed to the high electron density, Raman spectra of the films showed the sp3Raman peak shifted from 1325 to 1328.5 cm-1with narrower broadening. This behavior arose from an increase in grain size, corresponding to images from a field emission scanning electron microscope. Raman spectra of G-peak position and white light reflectometry showed a reduction in sp2carbon content of the film. The G-peak shifted from 1564 to 1541 cm-1and refractive index increased from 1.84 to 2.16. The formation of the films related to the concentrations of H and CH3radicals. The plasma impedance affected the radical concentrations.

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32

Crowder, Nathan A., Hugo Lehmann, Marise B. Parent y Douglas R. W. Wylie. "The Accessory Optic System Contributes to the Spatio-Temporal Tuning of Motion-Sensitive Pretectal Neurons". Journal of Neurophysiology 90, n.º 2 (agosto de 2003): 1140–51. http://dx.doi.org/10.1152/jn.00653.2002.

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The nucleus of the basal optic root (nBOR) of the accessory optic system (AOS) and the pretectal nucleus lentiformis mesencephali (LM) are involved in the analysis of optic flow that results from self-motion and are important for oculomotor control. These neurons have large receptive fields and exhibit direction selectivity to large moving stimuli. In response to drifting sine wave gratings, LM and nBOR neurons are tuned to either low spatial/high temporal frequencies (SF, TF) or high SF/low TF stimuli. Given that velocity = TF/SF, these are referred to as “fast” and “slow” neurons, respectively. There is a heavy projection from the AOS to the pretectum, although its function is unknown. We recorded the directional and spatio-temporal tuning of LM units in pigeons before and after nBOR was inactivated by tetrodotoxin injection. After nBOR inactivation, changes in direction preference were observed for only one of 18 LM units. In contrast, the spatio-temporal tuning of LM units was dramatically altered by nBOR inactivation. Two major effects were observed. First, in response to motion in the preferred direction, most (82%) neurons showed a substantially reduced (μ = –67%) excitation to low SF/high TF gratings. Second, in response to motion in the anti-preferred direction, most (63%) neurons showed a dramatically reduced (μ = –78%) inhibition to high SF/low TF gratings. Thus the projection from the nBOR contributes to the spatio-temporal tuning rather than the directional tuning of LM neurons. We propose a descriptive model whereby LM receives inhibitory and excitatory input from “slow” and “fast” nBOR neurons, respectively.

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33

Miller, Greg L. y Eric I. Knudsen. "Early Auditory Experience Induces Frequency-Specific, Adaptive Plasticity in the Forebrain Gaze Fields of the Barn Owl". Journal of Neurophysiology 85, n.º 5 (1 de mayo de 2001): 2184–94. http://dx.doi.org/10.1152/jn.2001.85.5.2184.

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Binaural acoustic cues such as interaural time and level differences (ITDs and ILDs) are used by many species to determine the locations of sound sources. The relationship between cue values and locations in space is frequency dependent and varies from individual to individual. In the current study, we tested the capacity of neurons in the forebrain localization pathway of the barn owl to adjust their tuning for binaural cues in a frequency-dependent manner in response to auditory experience. Auditory experience was altered by raising young owls with a passive acoustic filtering device that caused frequency-dependent changes in ITD and ILD. Extracellular recordings were made in normal and device-reared owls to characterize frequency-specific ITD and ILD tuning in the auditory archistriatum (AAr), an output structure of the forebrain localization pathway. In device-reared owls, individual sites in the AAr exhibited highly abnormal, frequency-dependent variations in ITD tuning, and across the population of sampled sites, there were frequency-dependent shifts in the representation of ITD. These changes were in a direction that compensated for the acoustic effects of the device on ITD and therefore tended to restore a normal representation of auditory space. Although ILD tuning was degraded relative to normal at many sites in the AAr of device-reared owls, the representation of frequency-specific ILDs across the population of sampled sites was shifted in the adaptive direction. These results demonstrate that early auditory experience shapes the representation of binaural cues in the forebrain localization pathway in an adaptive, frequency-dependent manner.

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34

Pinkhasov, Julia, Dora Acuna y Ram Singh. "Altered regulation of T-cell signal regulating (TSR) molecules in systemic autoimmunity (BA2P.129)". Journal of Immunology 192, n.º 1_Supplement (1 de mayo de 2014): 45.16. http://dx.doi.org/10.4049/jimmunol.192.supp.45.16.

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Abstract Recent evidence suggests that besides the T-cell receptor (TCR), there are other signal regulating molecules that play a pivotal role in establishing signal threshold during thymocyte selection through a process known as TCR tuning. We examined the expression level of a number of potential T-cell signal regulating (TSR) molecules in the MRL mouse model of multi-system autoimmune disease. We found the expression levels of negative regulators (CD5, CD6, CD2, GITR) that attenuate signal to be reduced, while positive regulators (CD26) that augment signal were increased on thymocytes in MRL mice compared to the C3H control mice. Thymocytes from MRL mice showed increased activation and phosphokinase signal upon ex vivo stimulation. Moreover, TSRs were further reduced on activated peripheral T cells after disease onset in the MRL mice. The reduced levels of these TSR molecules correlated with increased responsiveness to TCR-mediated signal upon ex vivo stimulation and phosphokinase detection. The reduced TSR expression levels were due to increased levels of ubiquitination, which led to targeted protein degradation. Importantly, co-stimulation with agonistic antibody against the TSR molecule CD5 reversed the hyper-responsiveness to TCR stimulation. The ability of T cells to alter their internal signal threshold by altering TSR expression may be a novel mechanism for T cells to escape peripheral tolerance and exacerbate autoimmune disease progression.

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35

Poenisch, Marion, Sandra Wille, Urs Schneider y Peter Staeheli. "Second-site mutations in Borna disease virus overexpressing viral accessory protein X". Journal of General Virology 90, n.º 8 (1 de agosto de 2009): 1932–36. http://dx.doi.org/10.1099/vir.0.011841-0.

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The X protein of Borna disease virus (BDV) is an essential factor that regulates viral polymerase activity and inhibits apoptosis of persistently infected cells. We observed that a BDV mutant which carries an additional X gene replicated well in cell culture only after acquiring second-site mutations that selectively reduced expression of the endogenous X gene. In rat brains, the virus acquired additional mutations which inactivated the ectopic X gene or altered the sequence of X. These results demonstrate that BDV readily acquires mutations if strong selection pressure is applied. They further indicate that fine-tuning of X expression determines viral fitness.

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36

Schweizer, Regina S., Raphael A. Aponte, Sabine Zimmermann, Annika Weber y Jochen Reinstein. "Fine Tuning of a Biological Machine: DnaK Gains Improved Chaperone Activity by Altered Allosteric Communication and Substrate Binding". ChemBioChem 12, n.º 10 (8 de junio de 2011): 1559–73. http://dx.doi.org/10.1002/cbic.201000786.

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37

Müller, James R., Andrew B. Metha, John Krauskopf y Peter Lennie. "Local Signals From Beyond the Receptive Fields of Striate Cortical Neurons". Journal of Neurophysiology 90, n.º 2 (agosto de 2003): 822–31. http://dx.doi.org/10.1152/jn.00005.2003.

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We examined in anesthetized macaque how the responses of a striate cortical neuron to patterns inside the receptive field were altered by surrounding patterns outside it. The changes in a neuron's response brought about by a surround are immediate and transient: they arise with the same latency as the response to a stimulus within the receptive field (this argues for a source locally in striate cortex) and become less effective as soon as 27 ms later. Surround signals appeared to exert their influence through divisive interaction (normalization) with those arising in the receptive field. Surrounding patterns presented at orientations slightly oblique to the preferred orientation consistently deformed orientation tuning curves of complex (but not simple) cells, repelling the preferred orientation but without decreasing the discriminability of the preferred grating and ones at slightly oblique orientations. By reducing responsivity and changing the tuning of complex cells locally in stimulus space, surrounding patterns reduce the correlations among responses of neurons to a particular stimulus, thus reducing the redundancy of image representation.

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38

Oda, Shigekazu, Yu Toyoshima y Mario de Bono. "Modulation of sensory information processing by a neuroglobin in Caenorhabditis elegans". Proceedings of the National Academy of Sciences 114, n.º 23 (23 de mayo de 2017): E4658—E4665. http://dx.doi.org/10.1073/pnas.1614596114.

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Sensory receptor neurons match their dynamic range to ecologically relevant stimulus intensities. How this tuning is achieved is poorly understood in most receptors. The roundworm Caenorhabditis elegans avoids 21% O2 and hypoxia and prefers intermediate O2 concentrations. We show how this O2 preference is sculpted by the antagonistic action of a neuroglobin and an O2-binding soluble guanylate cyclase. These putative molecular O2 sensors confer a sigmoidal O2 response curve in the URX neurons that has highest slope between 15 and 19% O2 and approaches saturation when O2 reaches 21%. In the absence of the neuroglobin, the response curve is shifted to lower O2 values and approaches saturation at 14% O2. In behavioral terms, neuroglobin signaling broadens the O2 preference of Caenorhabditis elegans while maintaining avoidance of 21% O2. A computational model of aerotaxis suggests the relationship between GLB-5–modulated URX responses and reversal behavior is sufficient to broaden O2 preference. In summary, we show that a neuroglobin can shift neural information coding leading to altered behavior. Antagonistically acting molecular sensors may represent a common mechanism to sharpen tuning of sensory neurons.

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39

De Sousa Trias, Carl, Mihai Petru Mitrea, Attilio Fiandrotti, Marco Cagnazzo, Sumanta Chaudhuri y Enzo Tartaglione. "Find the Lady: Permutation and Re-synchronization of Deep Neural Networks". Proceedings of the AAAI Conference on Artificial Intelligence 38, n.º 19 (24 de marzo de 2024): 21001–9. http://dx.doi.org/10.1609/aaai.v38i19.30091.

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Deep neural networks are characterized by multiple symmetrical, equi-loss solutions that are redundant. Thus, the order of neurons in a layer and feature maps can be given arbitrary permutations, without affecting (or minimally affecting) their output. If we shuffle these neurons, or if we apply to them some perturbations (like fine-tuning) can we put them back in the original order i.e. re-synchronize? Is there a possible corruption threat? Answering these questions is important for applications like neural network white-box watermarking for ownership tracking and integrity verification. We advance a method to re-synchronize the order of permuted neurons. Our method is also effective if neurons are further altered by parameter pruning, quantization, and fine-tuning, showing robustness to integrity attacks. Additionally, we provide theoretical and practical evidence for the usual means to corrupt the integrity of the model, resulting in a solution to counter it. We test our approach on popular computer vision datasets and models, and we illustrate the threat and our countermeasure on a popular white-box watermarking method.

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40

Sempere-Bigorra, Mar, Iván Julián-Rochina, Pilar Pérez-Ros, Emmanuel Navarro-Flores, Francisco Miguel Martínez-Arnau y Omar Cauli. "Relationship between Cognitive Impairment and Depressive Symptoms with Somatosensory Functions in Diabetic and Non-Diabetic Older Adults and Its Impact on Quality of Life". Life 13, n.º 9 (22 de agosto de 2023): 1790. http://dx.doi.org/10.3390/life13091790.

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Aging is an inevitable process that impacts the peripheral and central nervous systems and is considered one of the strongest risk factors for neurodegenerative diseases. In addition, when it also presents with diabetes mellitus, the risk of neurological damage may be further increased. This current study aimed to explore the relationships between peripheral sensory system decline and cognitive functions, the symptoms of depression, and quality of life (QoL) as metrics of central nervous system impairment in institutionalized older adults. A total of 95 individuals participated in this case-control study, which included diabetics and non-diabetics. The superficial sensory pathway was assessed in terms of thermal sensation, nociception, and non-discriminative touch, and the deep sensory pathway was evaluated by assessing vibration and light touch-pressure sensations. To assess function at the intellectual level, the Mini-Mental State Examination (MMSE) and Trail Making Test (TMT) cognitive functional tests were used, while the symptoms of depression and QoL were explored by employing the Yesavage Geriatric Depression Scale and EuroQol 5D questionnaire (EQ-5D), respectively. In the overall population analyses, altered thermal sensation was significantly associated with cognitive impairment (CI; p < 0.05). In turn, bivariate analyses and a binary logistic regression showed that the symptoms of depression and QoL were significantly related to altered vibratory sensation when assessed using a medical tuning fork (p < 0.05). In the group of diabetic patients, those with CI also had significantly lower thermal sensation (p < 0.05) and non-discriminative touch sensation, although this was only a trend (p = 0.055). Diabetics with depression had a significantly worse non-discriminative touch (p < 0.05) and vibratory sensation when tested with a tuning fork (p < 0.05). In addition, poorer QoL was associated with reduced sensitivity to heat (p < 0.05), light touch pressure (p < 0.05), and vibrations when assessed either with a tuning fork (p < 0.05) or a biothesiometer (p < 0.05). In contrast, no relationships were found between sensory functions and cognitive assessments in non-diabetic patients. These findings indicate that superficial sensitivity damage was related to CI, while deep sensation alterations were related to depression and poor QoL, with diabetes apparently further strengthening these relationships.

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41

Asakura, Yoko, Eiichiro Kimura, Yoshihiro Usuda, Yoshio Kawahara, Kazuhiko Matsui, Tsuyoshi Osumi y Tsuyoshi Nakamatsu. "Altered Metabolic Flux due to Deletion of odhA causes l-Glutamate Overproduction in Corynebacterium glutamicum". Applied and Environmental Microbiology 73, n.º 4 (8 de diciembre de 2006): 1308–19. http://dx.doi.org/10.1128/aem.01867-06.

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ABSTRACT l-Glutamate overproduction in Corynebacterium glutamicum, a biotin auxotroph, is induced by biotin limitation or by treatment with certain fatty acid ester surfactants or with penicillin. We have analyzed the relationship between the inductions, 2-oxoglutarate dehydrogenase complex (ODHC) activity, and l-glutamate production. Here we show that a strain deleted for odhA and completely lacking ODHC activity produces l-glutamate as efficiently as the induced wild type (27.8 mmol/g [dry weight] of cells for the ohdA deletion strain compared with only 1.0 mmol/g [dry weight] of cells for the uninduced wild type). This level of production is achieved without any induction or alteration in the fatty acid composition of the cells, showing that l-glutamate overproduction can be caused by the change in metabolic flux alone. Interestingly, the l-glutamate productivity of the odhA-deleted strain is increased about 10% by each of the l-glutamate-producing inductions, showing that the change in metabolic flux resulting from the odhA deletion and the inductions have additive effects on l-glutamate overproduction. Tween 40 was indicated to induce drastic metabolic change leading to l-glutamate overproduction in the odhA-deleted strain. Furthermore, optimizing the metabolic flux from 2-oxoglutarate to l-glutamate by tuning glutamate dehydrogenase activity increased the l-glutamate production of the odhA-deleted strain.

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42

Priebe, Nicholas J. y Stephen G. Lisberger. "Constraints on the Source of Short-Term Motion Adaptation in Macaque Area MT. II. Tuning of Neural Circuit Mechanisms". Journal of Neurophysiology 88, n.º 1 (1 de julio de 2002): 370–82. http://dx.doi.org/10.1152/jn.2002.88.1.370.

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Neurons in area MT, a motion-sensitive area of extrastriate cortex, respond to a step of target velocity with a transient-sustained firing pattern. The transition from a high initial firing rate to a lower sustained rate occurs over a time course of 20–80 ms and is considered a form of short-term adaptation. In the present paper, we compared the tuning of the adaptation to the neuron's tuning to direction and speed. The tuning of adaptation was measured with a condition/test paradigm in which a testing motion of the preferred direction and speed of the neuron under study was preceded by a conditioning motion: the direction and speed of the conditioning motion were varied systematically. The response to the test motion depended strongly on the direction of the conditioning motion. It was suppressed in almost all neurons by conditioning motion in the same direction and could be either suppressed or enhanced by conditioning motion in the opposite direction. Even in neurons that showed suppression for target motion in the nonpreferred direction, the adaptation and response direction tuning were the same. The speed tuning of adaptation was linked much less tightly to the speed tuning of the response of the neuron under study. For just more than 50% of neurons, the preferred speed of adaptation was more than 1 log unit different from the preferred response speed. Many neurons responded best when slow motions were followed by faster motions (acceleration) or vice versa (deceleration), suggesting that MT neurons may encode information about the change of target velocity over time. Finally, adaptation by conditioning motions of different directions, but not different speeds, altered the latency of the response to the test motion. The adaptation of latency recovered with shorter intervals between the conditioning and test motions than did the adaptation of response size, suggesting that latency and amplitude adaptation are mediated by separate mechanisms. Taken together with the companion paper, our data suggest that short-term motion adaptation in MT is a consequence of the neural circuit in MT and is not mediated by either input-specific mechanisms or intrinsic mechanisms related to the spiking of individual neurons. The circuit responsible for adaptation is tuned for both speed and direction and has the same direction tuning as the circuit responsible for the initial response of MT neurons.

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43

Kageyama, Yuito, Yuya Tazaki, Hongyu An, Takashi Harumoto, Tenghua Gao, Ji Shi y Kazuya Ando. "Spin-orbit torque manipulated by fine-tuning of oxygen-induced orbital hybridization". Science Advances 5, n.º 11 (noviembre de 2019): eaax4278. http://dx.doi.org/10.1126/sciadv.aax4278.

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Current-induced spin-orbit torques provide an effective way to manipulate magnetization in spintronic devices, promising for fast switching applications in nonvolatile memory and logic units. Recent studies have revealed that the spin-orbit torque is strongly altered by the oxidation of heterostructures with broken inversion symmetry. Although this finding opens a new field of metal-oxide spin-orbitronics, the role of the oxidation in the spin-orbit physics is still unclear. Here, we demonstrate a marked enhancement of the spin-orbit torque induced by a fine-tuning of oxygen-induced modification of orbital hybridization. This is evidenced by a concomitant enhancement of the interface spin-orbit torque, interface spin loss, and interface perpendicular magnetic anisotropy within a narrow range of the oxidation level of metallic heterostructures. This result reveals the crucial role of the atomic-scale effects in the generation of the spin-orbit torques, opening the door to atomic-level engineering of the spin-orbit physics.

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44

Muthurasu, A. y V. Ganesh. "Tuning optical properties of nitrogen-doped carbon dots through fluorescence resonance energy transfer using Rhodamine B for the ratiometric sensing of mercury ions". Analytical Methods 13, n.º 15 (2021): 1857–65. http://dx.doi.org/10.1039/d1ay00068c.

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Fluorescence emission of a bright blue emitting nitrogen doped carbon dots (N-CDs) is altered with Rhodamine B (RhB) using FRET to yield blue, violet, pink, orange and red emission colors that are explored for the selective sensing of mercury ions.

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45

Richardson, Andrew G., Tommaso Borghi y Emilio Bizzi. "Activity of the same motor cortex neurons during repeated experience with perturbed movement dynamics". Journal of Neurophysiology 107, n.º 11 (1 de junio de 2012): 3144–54. http://dx.doi.org/10.1152/jn.00477.2011.

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Neurons in the primary motor cortex (M1) have been shown to have persistent, memory-like activity following adaptation to altered movement dynamics. However, the techniques used to study these memory traces limited recordings to only single sessions lasting no more than a few hours. Here, chronically implanted microelectrode arrays were used to study the long-term neuronal responses to repeated experience with perturbing, velocity-dependent force fields. Force-field–related neuronal activity within each session was similar to that found previously. That is, the directional tuning curves of the M1 neurons shifted in a manner appropriate to compensate for the forces. Next, the across-session behavior was examined. Long-term learning was evident in the performance improvements across multiple force-field sessions. Correlated with this change, the neuronal population had smaller within-session spike rate changes as experience with the force field increased. The smaller within-session changes were a result of persistent across-session shifts in directional tuning. The results extend the observation of memory traces of newly learned dynamics and provide further evidence for the role of M1 in early motor memory formation.

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46

Li, Roger W., Kayee So, Thomas H. Wu, Ashley P. Craven, Truyet T. Tran, Kevin M. Gustafson y Dennis M. Levi. "Monocular blur alters the tuning characteristics of stereopsis for spatial frequency and size". Royal Society Open Science 3, n.º 9 (septiembre de 2016): 160273. http://dx.doi.org/10.1098/rsos.160273.

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Our sense of depth perception is mediated by spatial filters at different scales in the visual brain; low spatial frequency channels provide the basis for coarse stereopsis, whereas high spatial frequency channels provide for fine stereopsis. It is well established that monocular blurring of vision results in decreased stereoacuity. However, previous studies have used tests that are broadband in their spatial frequency content. It is not yet entirely clear how the processing of stereopsis in different spatial frequency channels is altered in response to binocular input imbalance. Here, we applied a new stereoacuity test based on narrow-band Gabor stimuli. By manipulating the carrier spatial frequency, we were able to reveal the spatial frequency tuning of stereopsis, spanning from coarse to fine, under blurred conditions. Our findings show that increasing monocular blur elevates stereoacuity thresholds ‘selectively’ at high spatial frequencies, gradually shifting the optimum frequency to lower spatial frequencies. Surprisingly, stereopsis for low frequency targets was only mildly affected even with an acuity difference of eight lines on a standard letter chart. Furthermore, we examined the effect of monocular blur on the size tuning function of stereopsis. The clinical implications of these findings are discussed.

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47

Khan, Muhammad Yar, Yan Liu, Tao Wang, Hu Long, Miaogen Chen y Dawei Gao. "A First-Principle Study of Monolayer Transition Metal Carbon Trichalcogenides". Journal of Superconductivity and Novel Magnetism 34, n.º 8 (27 de julio de 2021): 2141–49. http://dx.doi.org/10.1007/s10948-021-05980-1.

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AbstractMonolayer MnCX3 metal–carbon trichalcogenides have been investigated by using the first-principle calculations. The compounds show half-metallic ferromagnetic characters. Our results reveal that their electronic and magnetic properties can be altered by applying uniaxial or biaxial strain. By tuning the strength of the external strain, the electronic bandgap and magnetic ordering of the compounds change and result in a phase transition from the half-metallic to the semiconducting phase. Furthermore, the vibrational and thermodynamic stability of the two-dimensional structure has been verified by calculating the phonon dispersion and molecular dynamics. Our study paves guidance for the potential applications of these two mono-layers in the future for spintronics and straintronics devices.

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48

Pershko, A. M. y I. I. Yarovenko. "Modern nutrigenomics and nutrigenetics and some metabolic aspects of pathogenesis in inﬂammatory bowel diseases: a look into the future". Experimental and Clinical Gastroenterology 183, n.º 11 (14 de noviembre de 2020): 113–17. http://dx.doi.org/10.31146/1682-8658-ecg-183-11-113-117.

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The implementation of the target setting for the treatment of inﬂammatory bowel diseases — the achievement of clinical and endoscopic remission in each case, even taking into account biological therapy drugs, is not always achievable. It is obvious that patients with ulcerative colitis and Crohn’s disease are genetically heterogeneous in nature, which is manifested by the formation of various clinical and genetic phenotypes and various proﬁles of altered intestinal microbiota. Modern dietetics and nutritionology can be the most important ﬁne-tuning tool in this chain of events and signiﬁcantly increase the eﬀectiveness of the therapy, equally contributing to both normalization of the intestinal microbial community and providing mechanisms for regulating gene expression (epigenetic eﬀect).

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Dudok, Barna, Linlin Z. Fan, Jordan S. Farrell, Shreya Malhotra, Jesslyn Homidan, Doo Kyung Kim, Celestine Wenardy et al. "Retrograde endocannabinoid signaling at inhibitory synapses in vivo". Science 383, n.º 6686 (marzo de 2024): 967–70. http://dx.doi.org/10.1126/science.adk3863.

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Endocannabinoid (eCB)–mediated suppression of inhibitory synapses has been hypothesized, but this has not yet been demonstrated to occur in vivo because of the difficulty in tracking eCB dynamics and synaptic plasticity during behavior. In mice navigating a linear track, we observed location-specific eCB signaling in hippocampal CA1 place cells, and this was detected both in the postsynaptic membrane and the presynaptic inhibitory axons. All-optical in vivo investigation of synaptic responses revealed that postsynaptic depolarization was followed by a suppression of inhibitory synaptic potentials. Furthermore, interneuron-specific cannabinoid receptor deletion altered place cell tuning. Therefore, rapid, postsynaptic, activity-dependent eCB signaling modulates inhibitory synapses on a timescale of seconds during behavior.

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Khatarkar, Subhash y Kamlesh Ahirwar. "Tuning Colossal Magnetoresistance Effect Through Chemical Substitution In Perovskite Manganites". International Journal of Membrane Science and Technology 10, n.º 4 (15 de septiembre de 2023): 2609–16. http://dx.doi.org/10.15379/ijmst.v10i4.3705.

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Objective: This research is focused on the colossal magnetoresistance (CMR) effect tunability via chemical substitution in perovskite manganites. The objective is to learn how changing the chemical structure of these compounds affect their magnetic and electronic characteristics particularly the CMR effect. Methods: Perovskite manganite materials were prepared by the chemical substitution method to tune the composition of transition metal ions and rare-earth elements. The structural, magnetic, and electronic characterizations were done by the means of X-ray diffraction, magnetization measurements, and electrical transport measurements. Results: The study showed that the selective chemical substitution within the perovskite structure could be used to modulate the CMR effect in manganite materials. Due to the differences in chemical structure the magnetic ordering, charge carrier concentration and electronic band structure are altered which in turn influence the magnitude of the CMR effect. For example, specific chemical substitutions were shown to remarkably strengthen the CMR effect, leading to better magnetoresistance characteristics. Conclusion: This study demonstrates the possibility of tuning the CMR effect by the chemical substitution of Mn perovskite materials. By manipulating the chemical composition, it is achievable to fine-tune the magnetic and electronic characteristics for various spintronics, magnetic sensors and other devices that need high magnetoresistance effects. The results help to gain more knowledge about CMR in manganite systems and provide the guidance for the research on improving their performance.

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