Search results for "ACTIVATION"
showing 10 items of 2079 documents
Sequential conformational transitions and α-helical supercoiling regulate a sensor histidine kinase
2017
Sensor histidine kinases are central to sensing in bacteria and in plants. They usually contain sensor, linker, and kinase modules and the structure of many of these components is known. However, it is unclear how the kinase module is structurally regulated. Here, we use nano- to millisecond time-resolved X-ray scattering to visualize the solution structural changes that occur when the light-sensitive model histidine kinase YF1 is activated by blue light. We find that the coiled coil linker and the attached histidine kinase domains undergo a left handed rotation within microseconds. In a much slower second step, the kinase domains rearrange internally. This structural mechanism presents a t…
New Biologically Active Triterpene-Saponins fromRandia dumetorum
1990
Two new triterpene-saponins, 3-O-[O-beta-D-glucopyranosyl-(1----4)-O-beta-D-glucopyranosyl-(1----3)-( beta- D-glucuronopyranosyl)]oleanolic acid (1), 3-O-[O-beta-D-glucopyranosyl-(1----6)-O-beta-D-glucopyranosyl- (1----3)-(beta-D-glucuronopyranosyl)]oleanolic acid (2) together with five known saponins (3-7) were isolated from the methanolic extract of the fruits of Randia dumetorum (Retz) Lam. (Rubiaceae). Their structures were established on the basis of chemical and spectral data. The compounds 1, 3, 4, 5 were found to enhance significantly the proliferation of human lymphocytes in vitro. The crude saponin fraction showed haemolytic, molluscicidal, and immunostimulating activities.
Hypertrophic agonists induce the binding of c-Fos to an AP-1 site in cardiac myocytes: implications for the expression of GLUT1
2003
Objectives: Serum is among the agents known to induce hypertrophy of cardiac myocytes, which occurs concomitant with an increase in AP-1-mediated transcription. We have examined if this effect correlates with changes in the relative abundance of particular AP-1 heterodimers, as their exact composition under these conditions is unknown. Furthermore, we obtained insight on the specific role of c-Fos from studying the induction of the glucose transporter GLUT1 by serum in fibroblasts. Methods: We characterised the AP-1 heterodimers expressed in neonatal cardiac myocytes by supershift electrophoretic mobility shift assay (EMSA) analysis. Quantitative changes in transcription were measured using…
Ligand Diversity of Human and Chimpanzee CYP3A4: Activation of Human CYP3A4 by Lithocholic Acid Results from Positive SelectionS⃞
2009
For currently unknown reasons, the evolution of CYP3A4 underwent acceleration in the human lineage after the split from chimpanzee. We investigated the significance of this event by comparing Escherichia coli-expressed CYP3A4 from humans, chimpanzee, and their most recent common ancestor. The expression level of chimpanzee CYP3A4 was ∼50% of the human CYP3A4, whereas ancestral CYP3A4 did not express in E. coli. Steady-state kinetic analysis with 7-benzyloxyquinoline, 7-benzyloxy-4-(trifluoromethyl)coumarin (7-BFC), and testosterone showed no significant differences between human and chimpanzee CYP3A4. Upon addition of α-naphthoflavone (25 μM), human CYP3A4 showed a slightly decreased substr…
Revealing the unique features of each individual's muscle activation signatures
2021
International audience; There is growing evidence that each individual has unique movement patterns, or signatures. The exact origin of these movement signatures, however, remains unknown. We developed an approach that can identify individual muscle activation signatures during two locomotor tasks (walking and pedalling). A linear support vector machine was used to classify 78 participants based on their electromyographic (EMG) patterns measured on eight lower limb muscles. To provide insight into decision-making by the machine learning classification model, a layer-wise relevance propagation (LRP) approach was implemented. This enabled the model predictions to be decomposed into relevance …
MRI (Magnetic Resonance Imaging) in Psychiatry
2001
In recent years, structural and functional magnetic resonance imaging has opened up new avenues to the study of psychiatric disorders. A number of structural changes characteristic for different psychiatric diseases could be delineated by the use of magnetic resonance imaging (MRI). Functional magnetic resonance imaging (fMRI) enables the in vivo investigation of cerebral neuronal activation under cognitive or behavioral activation paradigms. Magnetic resonance spectroscopy (MRS) allows for the study of defined neurochemical substances or pharmacological agents in the human brain. This article presents an overview of the basic principles of the different MRI techniques and representative re…
Studying the evolution of neural activation patterns during training of feed-forward ReLU networks
2021
The ability of deep neural networks to form powerful emergent representations of complex statistical patterns in data is as remarkable as imperfectly understood. For deep ReLU networks, these are encoded in the mixed discrete–continuous structure of linear weight matrices and non-linear binary activations. Our article develops a new technique for instrumenting such networks to efficiently record activation statistics, such as information content (entropy) and similarity of patterns, in real-world training runs. We then study the evolution of activation patterns during training for networks of different architecture using different training and initialization strategies. As a result, we see …
Silver-Catalyzed C-C Bond Formation between Methane and Ethyl Diazoacetate in Supercritical CO2
2011
Even in the context of hydrocarbons’ general resistance to selective functionalization, methane’s volatility and strong bonds pose a particular challenge. We report here that silver complexes bearing perfluorinated indazolylborate ligands catalyze the reaction of methane (CH4) with ethyl diazoacetate (N2CHCO2Et) to yield ethyl propionate (CH3CH2CO2Et). The use of supercritical carbon dioxide (scCO2) as the solvent is key to the reaction’s success. Although the catalyst is only sparingly soluble in CH4/CO2 mixtures, optimized conditions presently result in a 19% yield of ethyl propionate (based on starting quantity of the diazoester) at 40°C over 14 hours.
Small molecule inhibitors of Apaf-1-related caspase- 3/-9 activation that control mitochondrial-dependent apoptosis
2006
10 pages, 5 figures.-- PMID: 16341125 [PubMed].-- Available online Dec 9, 2005.
In vivo impact of cytomegalovirus evasion of CD8 T-cell immunity: Facts and thoughts based on murine models
2010
Cytomegaloviruses (CMVs) co-exist with their respective host species and have evolved to avoid their elimination by the hosts' immune effector mechanisms and to persist in a non-replicative state, known as viral latency. There is evidence to suggest that latency is nevertheless a highly dynamic condition during which episodes of viral gene desilencing, which can be viewed as incomplete reactivations, cause intermittent antigenic activity that stimulates CD8 memory-effector T cells and drives their clonal expansion. These T cells are supposed to terminate reactivation before completion of the productive viral cycle. In this view, CMVs do not "evade" their respective host's immune response bu…