Endothelial dysfunction as assessed by flow-mediated dilation in patients with cardiac syndrome X: role of inflammation.

BACKGROUND: Endothelial dysfunction, reduced coronary flow reserve and increased markers of inflammation are detectable in cardiac syndrome X (CSX). In this study we investigated the relation between inflammation and systemic endothelial function in CSX patients. METHODS: We studied 42 CSX patients (55 +/- 6 years, 14 men) and 20 healthy subjects (52 +/- 7 years, 9 men). Systemic endothelial function was assessed by flow-mediated dilation (FMD) of the brachial artery after 5-minute of forearm cuff inflation. Serum C-reactive protein (CRP) was measured by a high-sensitivity method. RESULTS: FMD was significantly lower in CSX patients compared to controls (4.8 +/- 4.4 vs. 13.7 +/- 4%, p < 0.001), whereas CRP levels were higher in CSX patients than in controls (2.7 +/- 2.4 vs. 0.7 +/- 0.4 mg/L, p = 0.001). In CSX patients FMD showed a significant inverse correlation with CRP levels, even after adjustment for potentially confounding variables (r = -0.34, p = 0.006). CONCLUSION: An impaired FMD is detectable in CSX patients, suggesting a generalized abnormality in vascular function. Subclinical inflammation se is to play a significant role in the impairment of endothelium-dependent vasodilator function of these patients.

Physical aspects of the weakly hydrated protein surface.

We review the physical properties of water on the surface of weakly hydrated proteins and present some theoretical models used to understand them. The first part concerns mainly structural properties and introduces a model for two-dimensional clusters of water molecules. The second part is devoted to dynamical properties of the hydrated protein surface. Dielectric measurements which provide an evidence for proton conductivity due to the percolation of the network of surface water molecules and for the glass dynamics of migrating protons when temperature is lowered are reviewed. These results can be associated with the concept of frustration and analyzed with two models, an Ising model to describe the proton jumps and the model of two-dimensional surface water which exhibits a glassy dynamiques of the water molecules. Biological implications of these properties of hydration water are briefly discussed.

1/f noise and dynamical heterogeneity in glasses.

We investigate the relationship between two experimental sets of data related to dynamical heterogeneity, the coefficient alpha of 1/f(alpha) dipolar noise derived from the nonexponentiality of the dielectric or magnetic response near and above the mean relaxation time, and the range Delta(z) of the relaxation times. We find that in different classes of glasses, including spin and proton glasses, relaxor materials, and glass-forming liquids, this relationship exhibits the same trend.

Dielectric 1/f noise of proton glass on a hydrated protein surface.

From nonexponentiality of dielectric relaxation detected in hydrated lysozyme powder we evaluate the power spectrum x(2)(omega) of the fluctuating dipole moment X(2) of one macromolecule, due to the glass of protons migrating on the protein surface. Near room temperature, the contribution to the total dipole moment by the integrated strength of the 1/f(alpha) noise in the frequency range from 10(4) to 10(6) Hz, is well consistent with early Kirkwood's predictions in solution and more recent computations. The biochemical significance of the nonequilibrium region near the Vogel-Fulcher temperature T0 approximately 268 K calls for further investigations.

Proton glass freezing in hydrated lysozyme powders.

At room temperature, the dielectric relaxation of hydrated powder of the protein lysozyme is known to be due to protons migrating between ionized side chains. A recent study of this relaxation at lower temperatures suggested a behavior typical of proton glasses. An analysis of the complex dielectric susceptibility by a temperature-frequency plot presented here has revealed that ergodicity is broken due to the divergence of the longest relaxation time at 266 K, indicating specifically that this hydrated protein is a proton glass. A change in the temperature behavior of the static dielectric constant and the average relaxation frequency at 273 K indicates a further transition occurring at this temperature, whose nature remains to be investigated.

Cooperative charge fluctuations by migrating protons in globular proteins.

A review of the hydrogen bonded network on the protein surface shows the presence of a charged complex system with parallel and competitive interactions, including ionizable side-chains, migrating protons, bound water and nearby backbone peptides. This system displays cooperative effects of dynamical nature, reviewed for lysozyme as a case. By increasing the water coverage of the protein powder, the bound water cluster exhibits a percolative transition, detectable by the onset of large water-assisted displacements of migrating protons, with a parallel emergence of protein mobility and biological function. By lowering the temperature, migrating protons exhibit a glassy dielectric relaxation in the low frequency range, pointing to a frustration by competing interactions similar to that observed in spin glasses and fragile glass forming liquids. The observation of these dissipative processes implies the occurrence of spontaneous charge fluctuations. A simplified model of the protein surface, where conformational and ionizable side-chain fluctuations are averaged out, is used to discuss the statistical physics of these cooperative effects. Some biological implications of this dynamical cooperativity for enzymatic activity are briefly suggested at the end.

Proton tunneling in hydrated biological tissues near 200 K.

We measure the protonic conductivity in water clusters adsorbed on intact samples of viable biological samples (corn embryo and endosperm, Artemia cysts, and Typha pollen) below room temperature. In the low-temperature region, the conductivity increases with temperature as exp T6, in agreement with prediction by the theory of dissipative quantum tunneling. We detect the onset of this effect near 180 K, where a glass transition in the hydrated protein matrix is known to take place. Above 220 K other transitions are superimposed onto this simple behavior.

Dielectric properties of Artemia cysts at low water contents. Evidence for a percolative transition.

Cellular cysts of the crustacean Artemia provide a useful model for studies on water-dependent mechanisms in cellular function because they can undergo reversible cycles of dehydration-rehydration. We explored their dielectric behavior over the frequency range of 10 kHz to 1 MHz, at water contents between near zero and 0.5 g H2O/g dry weight (g/g). The dc conductivity and static dielectric permittivity were evaluated from electrostatic analysis of data obtained with a three-layered capacitor. Below cyst hydrations of 0.05 g/g, negligible dielectric response was observed at all frequencies. Between 0.05 and 0.25 g/g the permittivity increased sharply then reached a near plateau up to cyst hydrations close to 0.35 g/g, above which a second abrupt increase occurred. Values for the dielectric loss (tan delta) exhibited frequency-dependent peaks over the hydration range of 0.05-0.3 g/g, followed by an abrupt increase near 0.35 g/g, an hydration at which metabolism is first initiated in this system. These hydration-dependent dielectric changes are compared with previous studies on the biology and physics of this system, and evaluated by a model involving percolative ionic (likely protonic) conduction. Percolative behavior is characterized by a sharp increase in conductivity at a critical threshold of hydration (hc) according to a power law in which the exponent, t, equals 1.65 for a three-dimensional infinite lattice. For the Artemia cyst, t = 1.64 above hc = 0.35 g/g, which is in excellent agreement with theory. These results are compared to similar studies on lysozyme which also exhibits percolative behavior connected with the onset of biological function.

Two-dimensional protonic percolation on lightly hydrated purple membrane.

The capacitance and dielectric loss factor were measured for a sample of purple membrane of Halobacterium halobium as a function of hydration level (0.017 to >0.2 g of water/g of membrane) and frequency (10 kHz to 10 MHz). The capacitance and the derived conductivity show explosive growth above a threshold hydration level, h(c) approximately 0.0456. The conductivity shows a deuterium isotope effect, H/(2)H = 1.38, in close agreement with expectation for a protonic process. The level h(c) is frequency independent and shows no deuterium isotope effect. These properties are analogous to those found for lysozyme in a related study. Protonic conduction for the purple membrane can be considered, as for lysozyme, within the framework of a percolation model. The critical exponent, t, which describes the conductivity of a percolative system near the threshold, has the value 1.23. This number is in close agreement with expectation from theory for a two-dimensional percolative process. The dielectric properties of the purple membrane are more complex than those of lysozyme, seen in the value of h(c) and in the frequency and hydration dependence of the loss factor. There appear to be preferred regions of proton conduction. The percolation model is based upon stochastic behavior of a system partially populated with conducting elements. This model suggests that ion transport in membranes and its control can be based on pathways formed of randomly connected conducting elements and that a fixed geometry (a proton wire) is not the only possible basis for a mechanism of conduction.

[Echocardiographic aspects of false intraventricular tendons]. / Aspetti ecocardiografici dei falsi tendini intraventricolari.

A series of 4260 consecutive echocardiographic examinations, performed in 5 Cardiological Centers was examined, identifying 125 intraventricular false tendons (FTs) in 100 cases (55 normals and 45 with heart disease) of whom 31 were female and 69 male, aged 3 to 82 years. An anatomo-morphological study was possible in 9 cases, dead for stroke or heart failure, on autopsy, and in 7, on heart surgery. A phonocardiogram was performed in all normals and in 20 patients. On echocardiography, FTs appeared as an echo-producing string-like structure, straight between the septum and the ventricular free wall, mobile during the cardiac cycle, without systolic thickening and any relation with the atrioventricular valvular apparatus. The prevalence of FTs was 2.3%; it was 3.2% to 5.3% in younger people. FTs were located in the right ventricle (4 cases), left ventricle (95 cases) or in both (1 case). Their site was left apical (45 FTs), right apical (2 FTs), right (3 FTs) and left (20 FTs), upper septum-to-free wall (55 cases). In 1 case hypertrophy of trabeculae of the left ventricle was detected. FTs were single (79 cases), double (19 cases), multiple (2 cases), short (42 cases), long (58 cases), thick (45 cases) and thin (55 cases). They showed a membrane-like motion (thick FTs-45 cases) and a valve-like motion (thin FTs-55 cases). Innocent murmur was detected in 50 of 55 normals and related to thin FTs. Of 16 cases examined anatomically and histologically, FTs were fibrous in their distal portion and fibro-muscular in the proximal one in 12 cases, whereas they were entirely fibrous-muscular in 4 cases. The site and location of FTs detected by echo were confirmed by anatomy in all cases. In 4 cases other 9 FTs, not detected on echocardiography, were found. These data suggest that echocardiography is a useful tool to detect intraventricular FTs and differentiate them from other echo-producing structures. Although a relationship between FTs and heart disease has not been found, their presence could be responsible of innocent murmur in many normal subjects.

Proton percolation on hydrated lysozyme powders.

The framework of percolation theory is used to analyze the hydration dependence of the capacitance measured for protein samples of pH 3-10, at frequencies from 10 kHz to 4 MHz. For all samples there is a critical value of the hydration at which the capacitance sharply increases with increase in hydration level. The threshold h(c) = 0.15 g of water per g of protein is independent of pH below pH 9 and shows no solvent deuterium isotope effect. The fractional coverage of the surface at h(c) is in close agreement with the prediction of theory for surface percolation. We view the protonic conduction process described here for low hydration and previously for high hydration as percolative proton transfer along threads of hydrogen-bonded water molecules. A principal element of the percolation picture, which explains the invariance of h(c) to change in pH and solvent, is the sudden appearance of long-range connectivity and infinite clusters at the threshold h(c). The relationship of the protonic conduction threshold to other features of protein hydration is described. The importance of percolative processes for enzyme catalysis and membrane transport is discussed.

Protonic conductivity of hydrated lysozyme powders at megahertz frequencies.

Dielectric losses were measured for lysozyme powders of varied hydration level by a dielectric-gravimetric technique in the frequency range of 10 kHz to 10 MHz. The relaxation showed an isotope effect and pH dependence, indicating that the inferred conductivity is protonic. The transport process is likely restricted to the surface of individual macromolecules and involves shifting of protons between ionizable side chain groups of the protein. The time constant of the relaxation shows cooperativity in its seventh-order dependence on bound protons. The process develops in the hydration region critical for the onset of the catalytic properties of the enzyme. The binding of a substrate increases the relaxation time by a factor of 2. These observations suggest that the megahertz dispersion reflects behavior at the protein surface, specifically the cooperative channeling of proton flow through the active site, that may be of particular significance for the enzymatic and other functional properties of proteins.

Unidirectional circulation in a prebiotic photochemical cycle.

In this brief note, we suggest the possibility that a soliton-assisted unidirectional photochemical cycle has played a role in prebiotic evolution. This suggestion is based on a model calculation which is itself based on the detection of Davydov-type soliton overtones in acetanilide.

Soliton-assisted unidirectional circulation in a biochemical cycle.

The unidirectional circulation of an enzyme round a working cycle can be understood in terms of the formation and decay of a soliton that acts as a ligand for the protein and for which the surrounding heat bath serves as a sink. An experimental confirmation of this interpretation is suggested in which the soliton is of the Davidov type and is created by infrared photon absorption as in recent experiments on acetanilide.