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At least 19 recordsLinked to original sources

PubMed2026

Reducing state anxiety with alpha-frequency transcranial alternating current stimulation.

BACKGROUND: Anxiety reactivity to acute stress is a transdiagnostic vulnerability factor. We tested whether a single session of alpha-frequency transcranial alternating current stimulation (tACS) targeting the frontoparietal control network reduces stress-evoked state anxiety in healthy adults. METHODS: In a randomized, blinded, sham-controlled study, 42 participants (mean age 58.9 years) completed an acute stress task before and after stimulation. The task was an adapted moving-circles paradigm in which circle collisions triggered a brief aversive event (mild electric shock plus unpleasant noise and a white flash). Active stimulation consisted of 20 min of 10-Hz tACS (2.0 mA/channel; 30-s ramp up/down) delivered via electrodes at F3, P3, Cz, and T7 (0° phase at F3/P3; 180° at Cz/T7). Sham stimulation used the same montage and ramp periods but no sustained current. RESULTS: State anxiety showed a significant Time × Protocol interaction (F(1,35) = 4.22, p = .047): STAI-S decreased after active tACS (Δ = -3.16) but increased slightly after sham (Δ = +1.17). Perceived stress appraisal (SAAS) did not change. Resting-state alpha power at F3/P3 showed no reliable pre-post effects. During the task, left-frontal relative alpha differed by protocol and showed a trend toward larger increases following active tACS. Electrodermal and pupil indices changed across sessions in both groups, with no differential stimulation effects. CONCLUSIONS: A single alpha-tACS session produced a modest, selective reduction in stress-evoked state anxiety, supporting oscillatory neuromodulation as a scalable approach to dampen anxiety reactivity.

Humans↗

PubMed2026

Tissue-Level Transcriptomic Entropy Reveals Organ-Specific Aging Patterns and Predicts Cancer Progression.

Although aging and cancer share complex molecular mechanisms, distinguishing causative factors from byproducts remains challenging. Here, we investigated the role of tissue transcriptomic entropy-a measure of transcriptional disorder-in aging and cancer processes by analyzing RNA-sequencing data from over 25,000 samples from human and mouse tissues. We found that entropy changes during aging are highly tissue-specific, with some tissues showing increased entropy while others exhibit decreased or stable entropy levels. Moreover, transcriptomic entropy strongly correlates with age-related processes, showing positive associations with proliferation, cellular senescence, somatic mutation burden, and cellular reprogramming, whereas it negatively correlates with stemness. In cancer, we observed that primary tumors generally display higher entropy than normal tissue, with its levels further increasing in metastatic stages. Cancer treatment modulated entropy patterns in multiple contexts, with changes suggesting a role for transcriptional complexity in tumor plasticity and therapy resistance. Elevated entropy levels predicted poor survival outcomes in multiple cancer types, suggesting its potential as a prognostic marker. Furthermore, differential expression analysis revealed that entropy-associated genes are enriched in developmental processes and depleted in metabolic pathways, indicating a possible link to cellular dedifferentiation. Finally, we found increased entropy in various age-related disorders beyond cancer, suggesting that transcriptomic entropy may be a common feature in age-related diseases. Our findings establish transcriptomic entropy as a fundamental parameter in aging and cancer progression, offering new insights into disease mechanisms.

Humans↗

PubMed1977

Vapor phase adsorption of water on hydroxyapatite.

Water vapor adsorption isotherms were determined gravimetrically on three hydroxyapatite sampel differing in preparation and with surface areas of 70.4, 22.5, and 3.0 M2/gm, respectively. Heats of adsorption for the first layer of water were found to be 13.3, 13.2, and 13.9 kcal/mole on these hydroxypatites. From repeated thermal desorption and adsorption cycles of water, stepwise adsorption was observed which diminished with each outgassing cycle until it disappeared after the fourth cycle. Cross-sectional area of adsorbed water molecule on hydroxyapatite surface was estimated at 11.5 A2. Standard free energies, isosteric heats, changes in enthalpy, and entropy of adsorption of water on HAP samples outgassed at 300 C were determined.

Adsorption↗

PubMed1992

Quantal analysis using maximum entropy noise deconvolution.

When applying quantal analysis to synaptic transmission it is often unclear how much of the measured postsynaptic signal fluctuation arises from random sampling and noise rather than from the probabilistic transmitter release process. Unconstrained noise deconvolution methods do not overcome this because they tend to overfit the data, often giving a misleading picture of the underlying process. Instead, maximum entropy deconvolution provides a solution which is the smoothest, or most featureless, distribution that is still compatible with the data, taking noise and sample size into account. A simple way of achieving this is described, together with results of Monte Carlo simulations which show that the features present in the maximum entropy solution usually reflect the process underlying the data and not random sampling or noise.

Algorithms↗

PubMed1992

Light scattering study of irradiated lipid bilayer.

Vesicular phospholipid bilayer membranes in the form of giant unilamellar vesicles (GUVs) of dipalmitoylphosphatidylcholine (DPPC) were irradiated with fast neutron fluences ranging from 10(4) to 10(7) n cm-2. The phase behaviour of both non-irradiated and irradiated GUVs was investigated using an angular light scattering technique. A model independent size distribution of the samples and their optical anisotropy (delta) were determined using a maximum entropy technique and the theory of light scattering from spherical shells composed of anisotropic cylindrical molecules arranged radially in the shells. The structural changes in the lipid bilayer exposed to fission neutrons are discussed on the basis of the damaging mechanisms of fast neutrons to both the hydrophobic and hydrophilic regions of the lipid bilayer.

1,2-Dipalmitoylphosphatidylcholine↗

PubMedDate not supplied

Thermodynamic parameters for the intramolecular disordered-to-beta transition of poly(L-tyrosine) in aqueous solution.

We have examined the disordered-to-beat transition of two samples of high molecular wieght poly(L-tyrosine), a polypeptide with an ionizing side chain, by potentiometric titration of solutions of this polymer in aqueous buffer. The degree of ionization was determined spectrophotometrically from the absorption of the tyrosinate anion at 293.5 nm. By using polymer solutions of high dilution the region of the conformational transition was separated from that of aggregation. As a consequence it was possible to obtain titration data for the intramolecular transition which we believe are free of interference from aggregation. For this transition we found that deltaHO=-1330 cal/mol of residue. The two samples gave values of -3.42+/-0.14 and -3.85+/-0.10 u for the change in entropy. Possible artifactual origins for this distinction have been examined and may be dicounted. Rather, it probably reflects a difference in the beta structures formed which depends on molecular weight.

Hydrogen-Ion Concentration↗

PubMed1978

Application of immersional calorimetry to investigation of solid-liquid interactions: microcrystalline cellulose-water system.

A comprehensive characterization of the specific solid-liquid interaction for microcrystalline cellulose and water is presented. The procedure consisted of a conjoint vapor adsorption and immersional wetting experiment. The following information was obtained with respect to the solid. Estimates of the total surface are (138 m2/g) and the external surface (9.2 m2/g) were calculated from the adsorption and immersion data, respectively. Existence of an energetically homogeneous surface was verified by a linear decrease in the heat of immersion of samples containing adsorbed moisture approximately up to monolayer capacity. Integral and differential free energy, enthalpy, and entropy changes accompanying the adsorption process were calculated, and a lack of swelling was substantiated by comparison with a similar study of cellulose fibers. Immersional hysteresis was observed, and its magnitude suggested that sorption hysteresis was of enthalpic as well as entropic origin. The experimental method is potentially valuable for routine characterization of hydrophilic powders.

Adsorption↗

PubMed1992

Pre-nucleation crystallization studies on aminoacyl-tRNA synthetases by dynamic light-scattering.

Dynamic light-scattering (DLS) studies on solutions of proteins approaching their precipitation point were made with asparaginyl- (NRSEC), leucyl- (LRSEC) and valyl- (VRSEC) tRNA synthetases from Escherichia coli. The three aminoacyl-tRNA synthetases have not been crystallized previously. As a control system, we used E. coli polypeptide elongation factor Tu (EF-Tu). Apart from the different proteins used here, the methods we employed differed from previous studies in that (1) instead of making a series of measurements on individual samples at various concentrations, the protein solutions were titrated with the precipitants, and (2) the results of the light-scattering measurements were analysed by a new maximum entropy procedure that calculates a particle size distribution in a highly reproducible way. The particle size distributions of protein solutions titrated with precipitants showed two major peaks in most cases. For both peaks, relative areas and mean diffusion coefficients were determined. The diffusion constants were corrected for the viscosity of the solutions. From comparing the results on the proteins known to crystallize (EF-Tu) with the amorphously precipitating systems (LRSEC, NRSEC) we find two necessary, but not sufficient, conditions for the formation of crystals: the diffusion coefficient of the monomer peak stays constant until very close to the precipitation point; the percentage of large aggregates stays small (less than 10% of the scattered light intensity) during the titration. For VRSEC, both ammonium sulphate and sodium citrate showed a low percentage of large aggregates and a constant diffusion coefficient of the main (protein monomer) peak below the precipitation point. This indicates that both would be possible precipitants for the crystallization of this enzyme. Crystallization trials using both these salts were carried out, and although no condition could as yet be found for obtaining crystals with ammonium sulphate solutions, crystals of the enzyme have been obtained with sodium citrate.

Amino Acyl-tRNA Synthetases↗

PubMed1992

Effect of NaCl addition on nanosecond O2 escaping reaction of myoglobin: evidences for the transition of myoglobin dynamic structure at 20 degrees C.

We studied the nanosecond (ns) geminate O2 escape reaction from the protein interior of myoglobin (Mb) to the solvent phase in the temperature range of 5-40 degrees C containing 0-0.1 M NaCl. In the flash photolysis experiments, we found that both the rate constant, kout, and its Arrhenius plot changed upon the variation of the NaCl concentration. In particular, it was noteworthy that the Arrhenius plot of kout dramatically changed in its slope, keeping the break at 20 degrees C, upon the addition of NaCl, indicating that the thermodynamic parameters such as an enthalpy of activation (delta H not equal to) and an entropy of activation (delta S not equal to) are different between above and below 20 degrees C, and that they are further altered upon the NaCl addition to the sample solution. From these results, we suggested that the Mb dynamic structure in the ns geminate O2 escape reaction is sensitively regulated by the interaction of the protein surface and the salt. The present study also showed that an inconsistency of the Arrhenius plot of kout between Chatfield et al. ((1990) J. Am. Chem. Soc. 112, 4680-4687) and us ((1990) J. Biol. Chem. 265, 18823-18828) is probably due to the difference in the solution condition.

Myoglobin↗

PubMedDate not supplied

[Effect of temperature and degree of hydration on the mobility of spin labels in surface layers of proteins].

The mobility of separate sites of the water-protein matrix depending on temperature and degree of hydration has been investigated by means of spin labels covalently attached to surface layers of proteins (alpha-chymotrypsin and human serum albumin) and also by a spin probe in a hydrophobic "pocket" of human serum albumin. The results obtained are compared with the data on the mobility of gamma-resonance labels (57Fe) firmly bound with the protein matrix in the same samples. At certain temperature and degree of hydration both spin and gamma-resonance label show an increase in mobility. With the degree of hydration increasing one may observe a simultaneous increase in energy and in entropy of activation: rotatory diffusion of spin labels, i. e., a compensation effect takes place which confirms the concept expressed earlier that cooperation of water-protein interactions is the main reason of CEF. It should be noted that at P/PS greater than 0.8 the values of delta E =7 divided by 10 kcal/mole, and delta S not equal to = 9 divided by 11 e. e. are specific to glycerol-like systems, i. e., under these conditions (P/Ps greater than 0.8) the water-protein layer has glycerol-like properties.

Calorimetry↗

PubMedDate not supplied

Microevolution in Ferrara: isonymy 1890-1990.

The distribution of surnames in the population of the town of Ferrara, as it existed in the memory banks of the Municipality Computer in June 1990, was studied by sex, age and place of birth of residents. Random isonymy was studied separately in persons born before 1901, and in persons born in the nine decades thereafter, ending with the period 1981-90. Isonymy was higher in the older age groups studied. Also other indicators of the abundance of surnames in the distribution, the common ecological indexes derived from entropy, were calculated and compared between age groups. It was found that redundancy, as isonymy, is larger in older age classes than in younger classes. Surname effective number was defined as the inverse of isonymy corrected for sample size, and it was observed that it is practically identical with Fisher's alpha. It was then possible to separate random isonymy into two components, so that for sample size N its formulation becomes Ir = 1/alpha + 1/N It was found that in Ferrara alpha increased significantly in time, indicating enrichment of surnames in the population in the century 1890-1990.

Age Factors↗

PubMed1991

Maximum entropy and drug absorption.

The application of maximum entropy to the calculation of drug absorption rates was introduced in an earlier paper. Here it is developed further, and the whole procedure is presented as a problem in scientific inference to be solved using Bayes' theorem. Blood samples do not need to be taken at equally spaced intervals, and no smoothing, interpolation, extrapolation, or other preprocessing of the data is necessary. The resulting input rate estimates are smooth and physiologically realistic, even with noisy data, and their accuracy is quantified. Derived quantities such as the proportion of the dose absorbed, and the mean and median absorption times, are also obtained, together with their error estimates. There are no arbitrarily valued parameters in the analysis, and no specific functional form, such as an exponential or polynomial, is assumed for the input rate functions.

Biological Availability↗

PubMed1991

An evaluation of new processing protocols for in vivo NMR spectroscopy.

In vivo NMR spectroscopy is often complicated with problems of low signal-to-noise, poor resolution, undefined peak shapes, and nonlinear baselines despite the efforts of investigators to optimize their experiments. Several data processing options are available to spectroscopists to enhance resolution and signal-to-noise and/or to flatten baselines. There is some question about how these processing protocols affect quantitative information. This paper evaluates five different processing protocols for their ability to extract quantitative information from a set of nonideal spectra. Three of the protocols involve recently developed statistical signal processing methods, maximum entropy Fourier spectral deconvolution, linear prediction singular value decomposition, and baseline deconvolution. These protocols are compared with the conventional processing methods of convolution difference and zeroing initial data points of the FID. The methods are evaluated by use of a quantitative 31P model sample and also are demonstrated on surface coil 31P data.

2,3-Diphosphoglycerate↗

PubMed1975

Dynamics of ligand binding to myoglobin.

Myoglobin rebinding of carbon monoxide and dioxygen after photodissociation has been observed in the temperature range between 40 and 350 K. A system was constructed that records the change in optical absorption at 436 nm smoothly and without break between 2 musec and 1 ksec. Four different rebinding processes have been found. Between 40 and 160 K, a single process is observed. It is not exponential in time, but approximately given by N(t) = (1 + t/to)-n, where to and n are temperature-dependent, ligand-concentration independent, parameters. At about 170 K, a second and at 200 K, a third concentration-independent process emerge. At 210 K, a concentration-dependent process sets in. If myoglobin is embedded in a solid, only the first three can be seen, and they are all nonexponential. In a liquid glycerol-water solvent, rebinding is exponential. To interpret the data, a model is proposed in which the ligand molecule, on its way from the solvent to the binding site at the ferrous heme iron, encounters four barriers in succession. The barriers are tentatively identified with known features of myoglobin. By computer-solving the differential equation for the motion of a ligand molecule over four barriers, the rates for all important steps are obtained. The temperature dependences of the rates yield enthalpy, entropy, and free-energy changes at all barriers. The free-energy barriers at 310 K indicate how myoglobin achieves specificity and order. For carbon monoxide, the heights of these barriers increase toward the inside; carbon monoxide consequently is partially rejected at each of the four barriers. Dioxygen, in contrast, sees barriers of about equal height and moves smoothly toward the binding site. The entropy increases over the first two barriers, indicating a rupturing of bonds or displacement of residues, and then smoothly decreases, reaching a minimum at the binding site. The magnitude of the decrease over the innermost barrier implies participation of heme and/or protein. The nonexponential rebinding observed at low temperatures and in solid samples implies that the innermost barrier has a spectrum of activation energies. The shape of the spectrum has been determined; its existence can be explained by assuming the presence of many conformational states for myoglobin. In a liquid at temperatures above about 230 K, relaxation among conformational states occurs and rebinding becomes exponential.

Binding Sites↗

PubMed2026

Matching-adjusted indirect comparison of fruquintinib versus ramucirumab in advanced gastric or gastroesophageal junction adenocarcinoma.

Aim: Fruquintinib (Fruq), a selective VEGFR 1/2/3 inhibitor, showed a significant progression-free survival (PFS) benefit in the Phase III FRUTIGA trial for advanced gastric/gastroesophageal junction (G/GEJ) adenocarcinoma. Ramucirumab (RAM), an anti-VEGFR2 antibody, demonstrated efficacy in the RAINBOW-Asia trial. This anchored matching-adjusted indirect comparison (MAIC) evaluated Fruq plus paclitaxel versus RAM plus paclitaxel as second-line therapy for G/GEJ adenocarcinoma in the absence of head-to-head trials. Materials & methods: Data from individual patients in the FRUTIGA study (N = 703) and aggregated data from the RAINBOW-Asia study (N = 440) were analyzed. Baseline characteristics were balanced using entropy balancing. The placebo plus paclitaxel (PBO + PTX) groups served as the common comparators. The primary outcome was PFS; secondary outcomes included overall survival, objective response rate (ORR) and disease control rate (DCR). Rates of treatment-emergent adverse events (TEAEs) were also compared as an exploratory outcome using an adjusted indirect risk difference. Sensitivity analyses included restricted mean survival time and simulated treatment comparison. Results: After weighting (effective sample size = 564), baseline covariates were balanced. The anchored MAIC demonstrated that Fruq + PTX significantly improved PFS compared with RAM + PTX (HR: 0.70; 95% CI: 0.51-0.96; p = 0.0280), corresponding to a 30% reduction in progression risk, with a significant restricted mean survival time benefit of 1.18 months at 20 months (95% CI: 0.08-2.27; p = 0.024). Fruq achieved significantly higher ORR (OR: 1.76, 95% CI: 1.16-2.68; p = 0.008) and DCR (OR: 1.94, 95% CI: 1.33-2.83; p < 0.001). Overall survival was similar (0.97; 95% CI: 0.73-1.30; p = 0.8640). Subgroup analyses showed PFS benefits with Fruq in patients with ECOG PS 1, peritoneal metastases and two or fewer metastatic sites. In sensitivity analysis, the simulated treatment comparison also suggested a PFS benefit for Fruq + PTX (HR: 0.40, 95% CI: 0.32-0.50; p < 0.0001). For any-grade TEAEs, the indirect comparison showed higher adjusted relative incidences of increased bilirubin with Fruq + PTX than with RAM + PTX (RD: 12.3%; 95% CI: 2.3-22.4%, p < 0.05) and of hypokalemia (RD: 9.0%; 95% CI: 1.5-16.4%, p < 0.05). For grade ≥3 TEAEs, the adjusted relative incidence of decreased body weight was higher with Fruq + PTX than with RAM + PTX (RD: 2.9%; 95% CI: 0.6-5.2%, p < 0.05). The adjusted relative incidences of increased AST, ALT and hypocalcemia were numerically lower in the fruquintinib group than in the RAM group. Conclusion: This MAIC indicates that Fruq + PTX may be more effective than RAM + PTX in second-line advanced G/GEJ adenocarcinoma, with potentially improved PFS, ORR and DCR, and similar overall survival. Safety analyses suggested generally comparable safety profiles across the two regimens. Fruq + PTX remains a valuable treatment option, offering important comparative evidence for clinical and health technology assessment decisions. Trial Registration: Clinicaltrials.gov identifiers: NCT07144995.

Adult↗

PubMed1992

Thermodynamics of protein-peptide interactions in the ribonuclease-S system studied by molecular dynamics and free energy calculations.

Hydrophobic interactions between the S-peptide and S-protein in the ribonuclease-S complex are probed using molecular dynamics simulations and free energy calculations. Three successive mutations at the buried position Met13 are simulated: Met----Leu, Leu----Ile, and Ile----Val, for which X-ray structures and experimental thermodynamic data are available. The calculations give theoretical estimates of the changes in binding free energies associated with these mutations. The calculated free energy differences are small (0-1.6 kcal/mol), in agreement with experiment. However the simulated structures deviate significantly from the experimental ones (mean deviation approximately 1.5-2 A), and a large uncertainty in the calculated free energies (1-2 kcal/mol) arises from the multiple minimum problem. Indeed, multiple conformations are available to the side chains around the mutation site, and the sampling of dihedral rotamer transitions is limited, despite long simulations. Fluctuations within each local minimum give rise to a small statistical error. However the uncertainty due to multiple conformations is much greater than the uncertainty due to random statistical errors. In our work, an artificial cancellation of errors arose because we studied conformations of the RNase complex and of the S-peptide that were very similar. In general, the criterion for a precise simulation is not merely to reduce the random statistical error, as has been suggested, but rather to sample all the important local minima along the mutation pathway, and to reduce the statistical error for each one. Our calculations suggest that the packing changes associated with the mutations are energetically small and localized, and largely cancel when the complex and the S-peptide are compared. Solvation of the methionine side chain partial charges in the S-peptide and the complex appear to be energetically equivalent, so that removing them (as in Met13----Leu, Ile, Val) does not affect binding. Enthalpy and entropy changes could not be estimated reliably.

Computer Simulation↗

PubMed1979

The binding of phenprocoumon to human plasma proteins.

By in vitro experiments with equilibrium dialysis and 5 micrograms PPC per ml an average of 99.7 +/- 0.2% was bound to serum proteins. The binding in a solution with the albumin concentration which was present in the serum samples did not differ from this binding or from the binding in plasma where coagulation was prevented with either heparin or citrate. The binding constant in albumin solutions at 37 degrees was 4.5 +/- 0.31/mol x 10(-5) and an average of 1.16 +/- 0.04 primary binding sites was found. The association constant for the PPC albumin interaction was temperature dependent and the results of thermodynamic calculations suggested a combined ionic and non-polar type of binding as the change in enthalpy contributed with 40% of change in free energy. A large positive entropy change was found (15.79 Kcal/mol/degree K). The addition of phytomenadione to albumin solutions and of menadione to plasma caused a considerable decrease in the protein bound fraction of PPC, indicating the relevance of a study concerning the possible clinical consequences of these interactions.

4-Hydroxycoumarins↗

PubMed1991

Formulas for threshold computations.

Given a continuous variable S, which density functions on two subgroups omega + and omega - of a population omega are known (with for instance a higher mean value on omega + than on omega -), we first define two strategies for classification in these groups; the first one (MWC) consists in determining a threshold alpha such that classifying in omega + when S greater than or equal to alpha, in omega - otherwise, leads to the highest percentage of well-classed elements. The second one consists in choosing the most probable group, given the observed value of S. We give mathematical formulas for the thresholds involved in these two strategies when the density functions, determined by the application of the maximum entropy principle, are those of normal distributions. These formulas prove that the two considered strategies are frequently equivalent, and we give simpler formulas when the partial variances of S on omega + and omega - are unknown or approximately equal. All the formulas are adapted to the case where a cost coefficient is introduced to display the unequal seriousness of the two possible errors (misclassification in omega + or omega -). Then we consider an example, where we see that the computed thresholds can be graphically validated from empirical curves and have the same performances on the learning sample and on a test sample.

Analysis of Variance↗