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1.
Phys Rev Lett ; 126(9): 091101, 2021 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-33750144

RESUMO

We perform a comprehensive study of Milky Way (MW) satellite galaxies to constrain the fundamental properties of dark matter (DM). This analysis fully incorporates inhomogeneities in the spatial distribution and detectability of MW satellites and marginalizes over uncertainties in the mapping between galaxies and DM halos, the properties of the MW system, and the disruption of subhalos by the MW disk. Our results are consistent with the cold, collisionless DM paradigm and yield the strongest cosmological constraints to date on particle models of warm, interacting, and fuzzy dark matter. At 95% confidence, we report limits on (i) the mass of thermal relic warm DM, m_{WDM}>6.5 keV (free-streaming length, λ_{fs}≲10h^{-1} kpc), (ii) the velocity-independent DM-proton scattering cross section, σ_{0}<8.8×10^{-29} cm^{2} for a 100 MeV DM particle mass [DM-proton coupling, c_{p}≲(0.3 GeV)^{-2}], and (iii) the mass of fuzzy DM, m_{ϕ}>2.9×10^{-21} eV (de Broglie wavelength, λ_{dB}≲0.5 kpc). These constraints are complementary to other observational and laboratory constraints on DM properties.

2.
Phys Rev Lett ; 124(10): 101102, 2020 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-32216401

RESUMO

In recent years, many γ-ray sources have been identified, yet the unresolved component hosts valuable information on the faintest emission. In order to extract it, a cross-correlation with gravitational tracers of matter in the Universe has been shown to be a promising tool. We report here the first identification of a cross-correlation signal between γ rays and the distribution of mass in the Universe probed by weak gravitational lensing. We use data from the Dark Energy Survey Y1 weak lensing data and the Fermi Large Area Telescope 9-yr γ-ray data, obtaining a signal-to-noise ratio of 5.3. The signal is mostly localized at small angular scales and high γ-ray energies, with a hint of correlation at extended separation. Blazar emission is likely the origin of the small-scale effect. We investigate implications of the large-scale component in terms of astrophysical sources and particle dark matter emission.

3.
Phys Rev Lett ; 122(17): 171301, 2019 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-31107093

RESUMO

The combination of multiple observational probes has long been advocated as a powerful technique to constrain cosmological parameters, in particular dark energy. The Dark Energy Survey has measured 207 spectroscopically confirmed type Ia supernova light curves, the baryon acoustic oscillation feature, weak gravitational lensing, and galaxy clustering. Here we present combined results from these probes, deriving constraints on the equation of state, w, of dark energy and its energy density in the Universe. Independently of other experiments, such as those that measure the cosmic microwave background, the probes from this single photometric survey rule out a Universe with no dark energy, finding w=-0.80_{-0.11}^{+0.09}. The geometry is shown to be consistent with a spatially flat Universe, and we obtain a constraint on the baryon density of Ω_{b}=0.069_{-0.012}^{+0.009} that is independent of early Universe measurements. These results demonstrate the potential power of large multiprobe photometric surveys and pave the way for order of magnitude advances in our constraints on properties of dark energy and cosmology over the next decade.

4.
Phys Rev Lett ; 123(18): 181301, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31763885

RESUMO

We report the first detection of gravitational lensing due to galaxy clusters using only the polarization of the cosmic microwave background (CMB). The lensing signal is obtained using a new estimator that extracts the lensing dipole signature from stacked images formed by rotating the cluster-centered Stokes QU map cutouts along the direction of the locally measured background CMB polarization gradient. Using data from the SPTpol 500 deg^{2} survey at the locations of roughly 18 000 clusters with richness λ≥10 from the Dark Energy Survey (DES) Year-3 full galaxy cluster catalog, we detect lensing at 4.8σ. The mean stacked mass of the selected sample is found to be (1.43±0.40)×10^{14}M_{⊙} which is in good agreement with optical weak lensing based estimates using DES data and CMB-lensing based estimates using SPTpol temperature data. This measurement is a key first step for cluster cosmology with future low-noise CMB surveys, like CMB-S4, for which CMB polarization will be the primary channel for cluster lensing measurements.

5.
J Relig Health ; 55(5): 1561-73, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26472654

RESUMO

Seventh-day Adventist (SDA) and non-SDA (21.3 and 78.7 %, respectively) individuals (n = 7172) participating in the Complete Health Improvement Program, a 30-day diet and lifestyle intervention, in North America (241 programs, 2006-2012) were assessed for changes in selected chronic disease risk factors: body mass index (BMI), blood pressure (BP), pulse, lipid profile and fasting plasma glucose (FPG). Reductions were greater among the non-SDA for BMI, pulse and blood lipids. Furthermore, the majority of non-SDA in the highest risk classifications for BP, lipids and FPG, but only some lipids among SDA, were able to show improvement by 20 % or more.


Assuntos
Dieta/métodos , Exercício Físico , Promoção da Saúde/métodos , Estilo de Vida , Avaliação de Programas e Projetos de Saúde/estatística & dados numéricos , Religião , Glicemia , Pressão Sanguínea , Índice de Massa Corporal , Doença Crônica/prevenção & controle , Feminino , Humanos , Lipídeos , Masculino , Pessoa de Meia-Idade , América do Norte , Satisfação do Paciente/estatística & dados numéricos , Protestantismo , Pulso Arterial , Fatores de Risco
6.
Phys Rev Lett ; 115(5): 051301, 2015 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-26274409

RESUMO

We present a mass map reconstructed from weak gravitational lensing shear measurements over 139 deg2 from the Dark Energy Survey science verification data. The mass map probes both luminous and dark matter, thus providing a tool for studying cosmology. We find good agreement between the mass map and the distribution of massive galaxy clusters identified using a red-sequence cluster finder. Potential candidates for superclusters and voids are identified using these maps. We measure the cross-correlation between the mass map and a magnitude-limited foreground galaxy sample and find a detection at the 6.8σ level with 20 arc min smoothing. These measurements are consistent with simulated galaxy catalogs based on N-body simulations from a cold dark matter model with a cosmological constant. This suggests low systematics uncertainties in the map. We summarize our key findings in this Letter; the detailed methodology and tests for systematics are presented in a companion paper.

7.
J Nutr Health Aging ; 11(3): 242-8, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17508101

RESUMO

BACKGROUND: To determine if a lifestyle change program can modify behavior to reduce sleep and stress disorders. METHODS: Analyses are based on 2,624 individuals aged 30 to 80 years from the Rockford, Illinois metropolitan area who completed a lifestyle evaluation at baseline and again after four weeks, following participation in a 40-hour educational course given over a four-week period. Participants receive instruction on the importance of making better lifestyle choices related to making long-term improvements in nutrition and physical activity and they learn ways to improve sleep and reduce stress in their lives. RESULTS: Significant percent decreases were observed in the number experiencing selected sleep or stress disorders from baseline to four weeks later for "sleeps restlessly" (-59%), "suffers from insomnia" (-64%), "feels under pressure" (-37%), "easily emotionally upset" (-52%), and "feels fearful or depressed" (-61%). Experiencing a selected sleep or stress disorder after four weeks among those who had the disorder at baseline was significantly more likely in those not physically active and/or not having lowered their BMI after four weeks. Changes in alcohol consumption and smoking did not significantly contribute to changes in the disorders. Those who failed to lower their coffee/tea use after four weeks were significantly more likely to have a sleep disorder and be easily emotionally upset. CONCLUSIONS: Changes in lifestyle behaviors after attending an educational program significantly reduced sleep and stress disorders in as little as four weeks, primarily explained by decreasing BMI and/or increasing exercise.


Assuntos
Exercício Físico/fisiologia , Comportamentos Relacionados com a Saúde , Estilo de Vida , Transtornos do Sono-Vigília/epidemiologia , Estresse Fisiológico/epidemiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Consumo de Bebidas Alcoólicas , Índice de Massa Corporal , Café , Depressão/epidemiologia , Depressão/etiologia , Depressão/prevenção & controle , Feminino , Educação em Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Transtornos do Sono-Vigília/etiologia , Transtornos do Sono-Vigília/prevenção & controle , Fumar , Estresse Fisiológico/etiologia , Estresse Fisiológico/prevenção & controle , Chá , Redução de Peso
8.
Phys Rev E ; 95(6-1): 062112, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28709202

RESUMO

Fluctuation-induced ("Casimir") forces caused by thermal and quantum fluctuations are investigated for ideal and imperfect Bose gases confined to d-dimensional films of size ∞^{d-1}×D under periodic (P), antiperiodic (A), Dirichlet-Dirichlet (DD), Neumann-Neumann (NN), and Robin (R) boundary conditions (BCs). The full scaling functions Υ_{d}^{BC}(x_{λ}=D/λ_{th},x_{ξ}=D/ξ) of the residual reduced grand potential per area φ_{res,d}^{BC}(T,µ,D)=D^{-(d-1)}Υ_{d}^{BC}(x_{λ},x_{ξ}) are determined for the ideal gas case with these BCs, where λ_{th} and ξ are the thermal de Broglie wavelength and the bulk correlation length, respectively. The associated limiting scaling functions Θ_{d}^{BC}(x_{ξ})≡Υ_{d}^{BC}(∞,x_{ξ}) describing the critical behavior at the bulk condensation transition are shown to agree with those previously determined from a massive free O(2) theory for BC=P,A,DD,DN,NN. For d=3, they are expressed in closed analytical form in terms of polylogarithms. The analogous scaling functions Υ_{d}^{BC}(x_{λ},x_{ξ},c_{1}D,c_{2}D) and Θ_{d}^{R}(x_{ξ},c_{1}D,c_{2}D) under the RBCs (∂_{z}-c_{1})ϕ|_{z=0}=(∂_{z}+c_{2})ϕ|_{z=D}=0 with c_{1}≥0 and c_{2}≥0 are also determined. The corresponding scaling functions Υ_{∞,d}^{P}(x_{λ},x_{ξ}) and Θ_{∞,d}^{P}(x_{ξ}) for the imperfect Bose gas are shown to agree with those of the interacting Bose gas with n internal degrees of freedom in the limit n→∞. Hence, for d=3, Θ_{∞,d}^{P}(x_{ξ}) is known exactly in closed analytic form. To account for the breakdown of translation invariance in the direction perpendicular to the boundary planes implied by free BCs such as DDBCs, a modified imperfect Bose gas model is introduced that corresponds to the limit n→∞ of this interacting Bose gas. Numerically and analytically exact results for the scaling function Θ_{∞,3}^{DD}(x_{ξ}) therefore follow from those of the O(2n)ϕ^{4} model for n→∞.

9.
Phys Rev E Stat Nonlin Soft Matter Phys ; 73(1 Pt 2): 016131, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16486240

RESUMO

We consider systems confined to a d-dimensional slab of macroscopic lateral extension and finite thickness L that undergo a continuous bulk phase transition in the limit L --> infinity and are describable by an O(n) symmetrical Hamiltonian. Periodic boundary conditions are applied across the slab. We study the effects of long-range pair interactions whose potential decays as bx-(d+sigma) as x --> infinity, with 2

10.
Phys Rev E ; 94(3-2): 036101, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27739847

RESUMO

In a recent paper [Phys. Rev. E 92, 012123 (2015)PLEEE81539-375510.1103/PhysRevE.92.012123], a modified d-dimensional Φ^{4} model was investigated that differs from the standard one in that the Φ^{4} term was replaced by a nonlocal one with a potential u(x-x^{'}) that depends on a parameter σ and decays exponentially as |x-x^{'}|→∞ on a scale |m|^{-1}<∞. The authors claim the upper critical dimension of this model to be d_{σ}=4+2σ. Performing a one-loop calculation, they arrive at expansions in powers of ε_{σ}=d_{σ}-d for critical exponents such as η and related ones to O(ε_{σ}) whose O(ε_{σ}) coefficients depend on σ and the ratio w=m^{2}/Λ^{2}, where Λ is the uv cutoff. It is shown that these claims are unfounded and based on misjudgments and an ill-conceived renormalization-group calculation.

11.
Biochim Biophys Acta ; 913(2): 185-94, 1987 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-3593738

RESUMO

The substrate-dependent kinetics of the carbon monoxide-inhibited cytochrome P-450 activity and its light reversibility is reinvestigated in microsomal preparations. In order to find out whether the substrate specificity is mediated by an isoenzyme-specific binding of carbon monoxide with different dissociation constants an experimental design has been chosen where it could be established that essentially the same isoenzyme component was involved in two different monooxygenase reactions, i.e., the O-dealkylation of 7-ethoxycoumarin and the 7-hydroxylation of coumarin. The dissociation constant kD(CO) of the ferrous cytochrome P-450 carbon monoxide complex is 6-fold higher in the presence of 7-ethoxycoumarin than in the presence of coumarin. But the light-induced relative changes of the Warburg partition coefficient for the 7-ethoxycoumarin deethylation and for coumarin 7-hydroxylation do not differ remarkably from each other. These relative changes are shown to represent the ratio of the photoinduced rate constant to the spontaneous rate constant of the dissociation for the ferrous cytochrome P-450 carbon monoxide complex. The differences in the dissociation constants are assigned to substrate specific effects on the carbon monoxide binding, indicating a substrate-specific change of the free binding enthalpy for carbon monoxide.


Assuntos
Monóxido de Carbono/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Isoenzimas/metabolismo , Microssomos Hepáticos/enzimologia , Animais , Benzoflavonas/farmacologia , Cumarínicos/metabolismo , Sistema Enzimático do Citocromo P-450/efeitos da radiação , Concentração de Íons de Hidrogênio , Isoenzimas/efeitos da radiação , Cinética , Metirapona/farmacologia , NADP/metabolismo , Especificidade por Substrato , Suínos
12.
Spectrochim Acta A Mol Biomol Spectrosc ; 61(6): 1153-61, 2005 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15741115

RESUMO

The fluorescence quenching of 6-propionyl-2-dimethylaminonaphtalene (PRODAN) and 6-dodecanoyl-2-dimethylaminonaphtalene (LAURDAN) by octadecyl rhodamine B (ORB) in a model system of small unilamellar vesicles (SUV) of dipalmitoylphosphatidyl-choline (DPPC) was investigated. Non-linear Stern-Volmer behaviour was observed in both systems in the gel phase (25 degrees C) and in the fluid phase (50 degrees C), resulting from association processes and from static quenching. The relative quenching efficiencies of both dyes depend on the phase state of the bilayer and indicate a deeper incorporation of PRODAN and LAURDAN into the membrane in its fluid phase than in its gel phase.


Assuntos
2-Naftilamina/análogos & derivados , 2-Naftilamina/química , Membrana Celular/fisiologia , Corantes Fluorescentes/química , Lauratos/química , Rodaminas/química , 1,2-Dipalmitoilfosfatidilcolina/química , Membrana Celular/química , Transferência de Energia , Bicamadas Lipídicas , Lipossomos , Espectrometria de Fluorescência
13.
Artigo em Inglês | MEDLINE | ID: mdl-26172668

RESUMO

The O(n) ϕ(4) model on a strip bounded by a pair of planar free surfaces at separation L can be solved exactly in the large-n limit in terms of the eigenvalues and eigenfunctions of a self-consistent one-dimensional Schrödinger equation. The scaling limit of a continuum version of this model is considered. It is shown that the self-consistent potential can be eliminated in favor of scattering data by means of appropriately extended methods of inverse scattering theory. The scattering data (Jost function) associated with the self-consistent potential are determined for the L=∞ semi-infinite case in the scaling regime for all values of the temperature scaling field t=(T-T(c))/T(c) above and below the bulk critical temperature T(c). These results are used in conjunction with semiclassical and boundary-operator expansions and a trace formula to derive exact analytical results for a number of quantities such as two-point functions, universal amplitudes of two excess surface quantities, the universal amplitude difference associated with the thermal singularity of the surface free energy, and potential coefficients. The asymptotic behaviors of the scaled eigenenergies and eigenfunctions of the self-consistent Schrödinger equation as function of x=t(L/ξ(+))(1/ν) are determined for x→-∞. In addition, the asymptotic x→-∞ forms of the universal finite-size scaling functions Θ(x) and ϑ(x) of the residual free energy and the Casimir force are computed exactly to order 1/x, including their x(-1)ln|x| anomalies.

14.
Artigo em Inglês | MEDLINE | ID: mdl-25768642

RESUMO

In a recent paper by D. Dantchev, J. Bergknoff, and J. Rudnick [Phys. Rev. E 89, 042116 (2014)], the problem of the Casimir force in the O(n) model on a slab with free boundary conditions, investigated earlier by us [Europhys. Lett. 100, 10004 (2012)], is reconsidered using a mean-spherical model with separate constraints for each layer. The authors (i) question the applicability of the Ginzburg-Landau-Wilson approach to the low-temperature regime, arguing for the superiority of their model compared to the family of ϕ(4) models A and B whose numerically exact solutions we determined both for values of the coupling constant 0

15.
Am J Cardiol ; 82(10B): 83T-87T, 1998 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-9860383

RESUMO

Vigorous cholesterol lowering with diet, drugs, or a combination has been shown to slow, arrest, or even reverse atherosclerosis. Residential lifestyle intervention programs have successfully lowered serum cholesterol levels and other coronary risk factors, but they have the disadvantages of high cost and difficulty with long-term adherence. Community-based risk-reduction programs have the potential to effect change at low cost and improve long-term adherence. To assess the effectiveness of, and to develop a model for, such programs, the community-based Coronary Health Improvement Project (CHIP) was developed in Kalamazoo, Michigan. In the intensive (30-day, 40-hour), hospital-based educational program, participants are encouraged to exercise 30 minutes a day and to embrace a largely unrefined plant-food-centered diet that is high in complex carbohydrates and fiber; very low in fat, animal protein, sugar, and salt; and virtually free of cholesterol. A total of 304 enrollees in the first program were at elevated risk of coronary artery and related diseases: 70% were > or =10% above their ideal weight, 14% had diabetes, 47% had hypertension, and 32% had a history of coronary artery disease. Of the enrollees, 288 "graduated" from the program (123 men, 165 women; mean age was 55+/-11 years). Various markers of disease risk, including serum blood lipids and fasting blood glucose concentrations, were measured before and after the program. At 4 weeks, overall improvements in the participants' laboratory test results, blood pressures, weights, and body mass indexes were highly significant (p <0.001). Triglyceride levels decreased significantly (p <0.05) in participants who had elevated triglyceride levels (>200 mg/dL in men, 200-299 mg/dL in women).


Assuntos
Serviços de Saúde Comunitária/organização & administração , Doença das Coronárias/prevenção & controle , Educação em Saúde/métodos , Estilo de Vida , Glicemia , Colesterol/sangue , Gorduras na Dieta/administração & dosagem , Exercício Físico , Feminino , Humanos , Masculino , Michigan , Pessoa de Meia-Idade , Fatores de Risco , Fatores Sexuais , Triglicerídeos/sangue
16.
Biophys Chem ; 90(2): 157-73, 2001 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-11352274

RESUMO

The perturbation of the lipid bilayer structure by tamoxifen may contribute to its multiple mechanisms of anticancer action not related to estrogen receptors. This study evaluates the effect of tamoxifen on structural characteristics of model membranes using differential scanning calorimetry (DSC), fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-[4-[trimethylammonium)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), as well as 6-dodecanoyl-2-dimethylaminonaphthalene (Laurdan) generalized polarization. The comparative measurements in multilammelar vesicles (MLV) prepared from dipalmitoylphosphatidylcholine (DPPC) revealed that tamoxifen decreases the phase transition temperature (Tm) paralleled by a broadening of the phase transition profile. In large unilamellar vesicles (LUV) prepared from egg yolk phosphatidylcholine (EPC), tamoxifen increased the lipid bilayer order predominantly in the outer bilayer region. From membrane permeability measurements, we conclude that the tamoxifen-induced release of entrapped carboxyfluorescein (CF) results from a permanent bilayer disruption and the formation of transient holes in the lipid bilayer.


Assuntos
2-Naftilamina/análogos & derivados , Bicamadas Lipídicas/química , Tamoxifeno/química , 1,2-Dipalmitoilfosfatidilcolina , Varredura Diferencial de Calorimetria , Permeabilidade da Membrana Celular/efeitos dos fármacos , Difenilexatrieno , Relação Dose-Resposta a Droga , Fluoresceínas/análise , Polarização de Fluorescência , Lauratos , Tamoxifeno/farmacologia , Temperatura
17.
Biophys Chem ; 67(1-3): 127-38, 1997 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-9397522

RESUMO

We have used differential scanning calorimetry and fluorescence anisotropy measurements to investigate the effect of five inhalation anaesthetics of diverse chemical structure (halothane, enflurane, n-pentane, chloroform and diethylether) on the phase behaviour of liposomes prepared from dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC), respectively. The incorporation of these anaesthetics induced a decrease of the phase transition temperature and/or a broadening of the phase transition peak depending on the transverse localisation of the investigated anaesthetic. At high anaesthetic concentrations we observed the disappearance of the pretransition peak and the appearance of a shoulder on the main phase transition peak due to the domain formation of the anaesthetics. An anaesthetic induced carboxyfluorescein efflux from the vesicle lumen was completed within a few minutes after the addition of the anaesthetics, probably resulting from a transient formation of membrane holes. All results are discussed with regard to the physicochemical properties of the anaesthetics applied.


Assuntos
1,2-Dipalmitoilfosfatidilcolina/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Anestésicos Inalatórios/química , Anestésicos Inalatórios/farmacologia , Dimiristoilfosfatidilcolina/química , Dimiristoilfosfatidilcolina/metabolismo , Bicamadas Lipídicas/química , Anestésicos Inalatórios/metabolismo , Varredura Diferencial de Calorimetria , Permeabilidade da Membrana Celular/efeitos dos fármacos , Fenômenos Químicos , Físico-Química , Fluoresceínas/química , Fluoresceínas/farmacocinética , Polarização de Fluorescência , Bicamadas Lipídicas/metabolismo , Lipossomos , Octanóis/química , Temperatura , Água/química
18.
Chem Phys Lipids ; 106(1): 79-88, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10878237

RESUMO

Pure 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC) or mixed DPPC:1,2-dipalmitoyl phosphatidyletanolamine (DPPE):1,2-dipalmitoyl diphosphatidylserine (DPPS) (17:5:3) liposomes were incorporated with 5 mol% dietary carotenoids (beta-carotene, lutein and zeaxanthin) or with cholesterol (16 and 48 mol%) in the absence or presence of 15 mol% carotenoids, respectively. The carotenoid incorporation yields ranged from 0.42 in pure to 0.72 in mixed phospholipid liposomes. They decreased significantly, from 3 to 14%, in the corresponding cholesterol-doped liposomes, respectively. Highest incorporation yields were achieved by zeaxanthin and lutein in phospholipid liposomes while in cholesterol-containing liposomes, lutein was highest incorporated. The effects on membrane structure and dynamics were determined by differential scanning calorimetry, steady-state fluorescence and anisotropy measurements. Polar carotenoids and cholesterol cause similar, dose-dependent effects: ordering and rigidification revealed by broadening of the transition peak, and increase of anisotropy. Membrane hydrophobicity is determined by cholesterol content and carotenoid polarity. In cholesterol-doped liposomes, beta-carotene is less incorporated than in cholesterol-free liposomes. Our observations suggest effects of carotenoids, even at much lower effective concentrations than cholesterol (8 to 80-fold), on membrane structure and dynamics. Although they are minor constituents of animal membranes, carotenoids may act as modulators of membrane phase transition, fluidity, polarity and permeability, and therefore, can influence the membrane physiology and pathology.


Assuntos
Carotenoides/química , Colesterol/química , Lipossomos/química , 1,2-Dipalmitoilfosfatidilcolina/química , Varredura Diferencial de Calorimetria , Polarização de Fluorescência , Técnicas In Vitro , Fluidez de Membrana , Fosfatidiletanolaminas/química , Fosfatidilserinas/química , Termodinâmica
19.
Chem Phys Lipids ; 72(1): 35-40, 1994 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-7923478

RESUMO

Membrane fluidity measurements based on excimer formation of pyrene and pyrene derivatives as a measure of lateral diffusion yield a decreased fluidity in the presence of proteins [1-3]. It was the aim of our study to investigate whether the reduced excimer formation is due to a rigidifying effect of proteins on the whole membrane or if the fluorophore mobility is mainly hindered in the immediate protein environment. Resonance energy transfer in microsomal membranes between intrinsic tryptophan residues and pyrene were used to study the excimer formation rate in the vicinity of proteins. The excimer-to-monomer fluorescence ratio at excitation via resonance energy transfer is lower than that observed for the direct excitation. The results suggest that, because of a reduced fluidity in the neighbourhood of proteins, pyrene and pyrene fatty acids do not diffuse homogeneously in the membrane plane. A fluidity gradient exists from the membrane proteins to the bulk lipid.


Assuntos
Membranas Intracelulares/fisiologia , Fluidez de Membrana , Microssomos Hepáticos/fisiologia , Animais , Transferência de Energia , Proteínas de Membrana/fisiologia , Pirenos/química , Espectrometria de Fluorescência , Suínos , Triptofano/química
20.
Chem Phys Lipids ; 112(1): 1-10, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11518567

RESUMO

Liposomes and beta-cyclodextrin (beta-CD) have been used as carriers for the incorporation of three dietary carotenoids (beta-carotene (BC), lutein (LUT) and canthaxanthin (CTX)) into plasma, mitochondrial, microsomal and nuclear membrane fractions from pig liver cells or the retinal epithelial cell line D407. The uptake dynamics of the carotenoids from the carriers to the organelle membranes and their incorporation yield (IY) was followed by incubations at pH 7.4 for up to 3 h. The mean IYs saturated between 0.1 and 0.9 after 10-30 min of incubation, depending on membrane characteristics (cholesterol to phospholipid ratio) and carotenoid specificity. Mitochondrial membranes (more fluid) favour the incorporation of BC (non-polar), while plasma membranes (more rigid) facilitate the incorporation of lutein, the most polar carotenoid. A high susceptibility of BC to degradation in the microsomal suspension was observed by parallel incubations with/without 2,6-di-t-buthyl-p-cresol (BHT) as antioxidant additive. The beta-CD carrier showed to be more effective for the incorporation of lutein while BC was incorporated equally into natural membranes either from liposomes or from cyclodextrins. The presence of cytosol in the incubation mixture had no significant effects on the carotenoid incorporations.


Assuntos
Carotenoides/química , Carotenoides/farmacocinética , Membrana Celular/metabolismo , Ciclodextrinas/química , Membranas Intracelulares/metabolismo , Lipossomos/química , Fígado/metabolismo , Epitélio Pigmentado Ocular/metabolismo , beta-Ciclodextrinas , Animais , Transporte Biológico , Cantaxantina/química , Cantaxantina/farmacocinética , Linhagem Celular , Núcleo Celular/metabolismo , Portadores de Fármacos , Humanos , Cinética , Luteína/química , Luteína/farmacocinética , Mitocôndrias/metabolismo , Membrana Nuclear/metabolismo , Suínos , beta Caroteno/química , beta Caroteno/farmacocinética
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