Sustainable dietetic models: strategies for communication and promotion

Global Burden of Disease identifies the makeup of diets as a significant risk factor for mortality and morbidity, with 11 million deaths and 255 million disability-adjusted life years attributable to dietary risk factors. 690 million people lack sufficient food and economic projections suggest that COVID-19 pandemic may add an additional 83 to 132 million people to the ranks of the undernourished, as the outbreak has exacerbated the global food flaws and insufficiencies, impacting the most vulnerable populations. Diets and related food systems also contribute to significant environmental degradation and climate change. Demand for animal-source foods is also increasing, particularly in emerging economies, which entails risks for the environment. 1.3 billion tons of food are wasted globally yearly, utilizing 38% of total energy consumption in the global food system. The real cost of acquiring enough nutrient-rich food to meet national dietary guidelines for a healthy diet exceeds available income for ∼38% of the world's population. A balanced diet that meets food-based dietary guidelines calls for even larger quantities of more costly food groups than would be needed just for nutrient adequacy, owing to their many functional attributes beyond just the essential nutrients that they contain. Faced with this scenario, there is urgent need for an appropriate strategy to increase people's awareness of the relationship between specific food choices and health and to facilitate the educational environment on this issue. Actual examples of current strategies for communication and promotion of healthy and sustainable diets will be discussed. With awareness and knowledge, clear and precise information, a supportive social environment, available and accessible healthy and sustainable food items, and the implementation of related policies, individuals have a great potential to achieve healthiness and environmental sustainability by choosing healthier and more sustainable foods.

Pressure-Induced Excitations in the Out-of-Plane Optical Response of the Nodal-Line Semimetal ZrSiS

The anisotropic optical response of the layered, nodal-line semimetal ZrSiS at ambient and high pressure is investigated by frequency-dependent reflectivity measurements for the polarization along and perpendicular to the layers. The highly anisotropic optical conductivity is in very good agreement with results from density-functional theory calculations and confirms the anisotropic character of ZrSiS. Whereas the in-plane optical conductivity shows only modest pressure-induced changes, we found strong effects on the out-of-plane optical conductivity spectrum of ZrSiS, with the appearance of two prominent excitations. These pronounced pressure-induced effects can neither be attributed to a structural phase transition according to our single-crystal x-ray diffraction measurements, nor can they be explained by electronic correlation and electron-hole pairing effects, as revealed by theoretical calculations. Our findings are discussed in the context of the recently proposed excitonic insulator phase in ZrSiS.

Polyphenols and obesity prevention: critical insights on molecular regulation, bioavailability and dose in preclinical and clinical settings

Obesity represents one of the most important public health challenges of the 21st century and is characterized by a multifactorial etiology in which environmental, behavioral, metabolic, and genetic factors work together. Despite the rapid increase in prevalence of obesity in the last decades, especially in children, it remains a preventable disease. To battle obesity a multisector approach promoting healthier lifestyle in terms of physical activity and nutrition is needed. Specifically, biologically active dietary compounds, as polyphenols, are able to modulate the expression of genes involved in the development and progression of obesity and its comorbidities as demonstrated by multiple studies using different obesity models. However, human studies focusing on the transcriptomic modulation by polyphenols in obese patients are still limited and do not often recapitulate the results obtained in preclinical setting likely due to the underestimation of some variables such as bioavailability, dose and form (native vs. metabolized) of polyphenols used. The aim of this review is to summarize the state-of-art of nutrigenomic in vitro, in vivo and ex vivo studies as well as clinical trials based on dietary polyphenols to fight obesity. We also critical discuss the variables to be considered to fill the gap between preclinical and clinical settings.

Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd2As2

Weyl fermions as emergent quasiparticles can arise in Weyl semimetals (WSMs) in which the energy bands are nondegenerate, resulting from inversion or time-reversal symmetry breaking. Nevertheless, experimental evidence for magnetically induced WSMs is scarce. Here, using photoemission spectroscopy, we observe that the degeneracy of Bloch bands is already lifted in the paramagnetic phase of EuCd2As2. We attribute this effect to the itinerant electrons experiencing quasi-static and quasi-long-range ferromagnetic fluctuations. Moreover, the spin-nondegenerate band structure harbors a pair of ideal Weyl nodes near the Fermi level. Hence, we show that long-range magnetic order and the spontaneous breaking of time-reversal symmetry are not essential requirements for WSM states in centrosymmetric systems and that WSM states can emerge in a wider range of condensed matter systems than previously thought.

Direct measurement of Ni incorporation into Fe3O4(001)

The normal incidence X-ray standing wave (NIXSW) technique has been used to follow the evolution of the adsorption geometry of Ni adatoms on the Fe₃O₄(001)-(√2 × √2)R45° surface as a function of temperature.

The normal incidence X-ray standing wave (NIXSW) technique has been used to follow the evolution of the adsorption geometry of Ni adatoms on the Fe₃O₄(001)-(√2 × √2)R45° surface as a function of temperature. Two primary surface region sites are identified: a bulk-continuation tetrahedral site and a sub-surface octahedral site, the latter site being preferred at higher annealing temperatures. The ease of incorporation is linked to the presence of subsurface cation vacancies in the (√2 × √2)R45° reconstruction and is consistent with the preference for octahedral coordination observed in the spinel compound NiFe₂O₄.

Three-Dimensional Electronic Structure of the Type-II Weyl Semimetal WTe_{2}

By combining bulk sensitive soft-x-ray angular-resolved photoemission spectroscopy and first-principles calculations we explored the bulk electron states of WTe_{2}, a candidate type-II Weyl semimetal featuring a large nonsaturating magnetoresistance. Despite the layered geometry suggesting a two-dimensional electronic structure, we directly observe a three-dimensional electronic dispersion. We report a band dispersion in the reciprocal direction perpendicular to the layers, implying that electrons can also travel coherently when crossing from one layer to the other. The measured Fermi surface is characterized by two well-separated electron and hole pockets at either side of the Γ point, differently from previous more surface sensitive angle-resolved photoemission spectroscopy experiments that additionally found a pronounced quasiparticle weight at the zone center. Moreover, we observe a significant sensitivity of the bulk electronic structure of WTe_{2} around the Fermi level to electronic correlations and renormalizations due to self-energy effects, previously neglected in first-principles descriptions.

Enhanced solubility and antibacterial activity of lipophilic fluoro-substituted N-benzoyl-2-aminobenzothiazoles by complexation with β-cyclodextrins

Some lipophilic fluoro-substituted N-benzoyl-2-aminobenzothiazole antibacterial agents have been evaluated for their activity in the presence of cyclodextrins (CDs) containing aqueous solutions where CDs are adopted as solubilizing excipients for improving the poor water solubility of these compounds. For such purpose both the natural β-CD and one of FDA/EMA approved CDs for parenteral use (i.e. HP-β-CD) have been employed. The solubility rank order observed was accounted for by thermal analysis (Differential Scanning Calorimetry) and FT-IR spectroscopy. The most promising compound was subjected to further NMR spectroscopic studies and molecular modelling simulations to verify the interactions between the guest molecule and the CD cavity. The assessment of the antibacterial activity of such compounds against selected Gram positive and Gram negative bacterial strains clearly showed that their antimicrobial effectiveness may, quite in all instances, be positively affected by complexation with β-CD and HP-β-CD. These results, which are in some ways in contrast with those already reported in the literature, are herein discussed on the basis of plausible mechanisms. Moreover, this investigation also reveals that the described methodology of complexing both lipophilic and hydrophilic antimicrobial agents with CDs may be an useful approach to enhance their effectiveness as well as a promising strategy to overcome even the microbial resistance problem.

Maximally localized Wannier functions in LaMnO3 within PBE + U, hybrid functionals and partially self-consistent GW: an efficient route to construct ab initio tight-binding parameters for eg perovskites

Using the newly developed VASP2WANNIER90 interface we have constructed maximally localized Wannier functions (MLWFs) for the e(g) states of the prototypical Jahn-Teller magnetic perovskite LaMnO(3) at different levels of approximation for the exchange-correlation kernel. These include conventional density functional theory (DFT) with and without the additional on-site Hubbard U term, hybrid DFT and partially self-consistent GW. By suitably mapping the MLWFs onto an effective e(g) tight-binding (TB) Hamiltonian we have computed a complete set of TB parameters which should serve as guidance for more elaborate treatments of correlation effects in effective Hamiltonian-based approaches. The method-dependent changes of the calculated TB parameters and their interplay with the electron-electron (el-el) interaction term are discussed and interpreted. We discuss two alternative model parameterizations: one in which the effects of the el-el interaction are implicitly incorporated in the otherwise 'noninteracting' TB parameters and a second where we include an explicit mean-field el-el interaction term in the TB Hamiltonian. Both models yield a set of tabulated TB parameters which provide the band dispersion in excellent agreement with the underlying ab initio and MLWF bands.

Tailor-made ultrathin manganese oxide nanostripes: 'magic widths' on Pd(1 1 N) terraces

The growth of ultrathin two-dimensional manganese oxide nanostripes on vicinal Pd(1 1 N) surfaces leads to particular stable configurations for certain combinations of oxide stripe and substrate terrace widths. Scanning tunneling microscopy and high-resolution low-energy electron diffraction measurements reveal highly ordered nanostructured surfaces with excellent local and long-range order. Density functional theory calculations provide the physical origin of the stabilization mechanism of 'magic width' stripes in terms of a finite-size effect, caused by the significant relaxations observed at the stripe boundaries.

Thickness dependent structural and electronic properties of CuO grown on SrTiO₃(100): a hybrid density functional theory study

We discuss the structural and electronic properties of tetragonal CuO grown on SrTiO₃(100) by means of hybrid density functional theory. Our analysis explains the anomalously large Cu-O vertical distance observed in the experiments (≈2.7 Å) in terms of a peculiar frustration between two competing local Cu-O environments characterized by different in-plane and out-of-plane bond lengths and Cu electronic populations. The proper inclusion of substrate effects is crucial to understanding the tetragonal expansion and to reproduce correctly the measured valence band spectrum for a CuO thickness of 3-3.5 unit cells, in agreement with the experimentally estimated thickness.

Molecular determinants of state-dependent block of voltage-gated sodium channels by pilsicainide

BACKGROUND AND PURPOSE

Pilsicainide, an anti-arrhythmic drug used in Japan, is described as a pure sodium channel blocker. We examined the mechanisms by which it is able to block open channels, because these properties may be especially useful to reduce hyperexcitability in pathologies characterized by abnormal sodium channel opening.

EXPERIMENTAL APPROACH

The effects of pilsicainide on various heterologously expressed human sodium channel subtypes and mutants were investigated using the patch clamp technique.

KEY RESULTS

Pilsicainide exhibited tonic and use-dependent effects comparable to those of mexiletine and flecainide on hNav1.4 channels. These use-dependent effects were abolished in the mutations F1586C and Y1593C within segment 6 of domain IV, suggesting that the interaction of pilsicainide with these residues is critical for its local anaesthetic action. Its affinity constants for closed channels (K(R)) and channels inactivated from the closed state (K(I)) were high, suggesting that its use-dependent block (UDB) requires the channel to be open for it to reach a high-affinity blocking site. Accordingly, basic pH, which slightly increased the proportion of neutral drug, dramatically decreased K(R) and K(I) values. Effects of pilsicainide were similar on skeletal muscle hNav1.4, brain hNav1.1 and heart hNav1.5 channels. The myotonic R1448C and G1306E hNav1.4 mutants were more and less sensitive to pilsicainide, respectively, due to mutation-induced gating modifications.

CONCLUSIONS AND IMPLICATIONS

Although therapeutic concentrations of pilsicainide may have little effect on resting and closed-state inactivated channels, it induces a strong UDB due to channel opening, rendering the drug ideally suited for inhibition of high-frequency action potential firing.

Polymeric forms of carbon in dense lithium carbide

The immense interest in carbon nanomaterials continues to stimulate intense research activities aimed at realizing carbon nanowires, since linear chains of carbon atoms are expected to display novel and technologically relevant optical, electrical and mechanical properties. Although various allotropes of carbon (e.g., diamond, nanotubes, graphene, etc) are among the best-known materials, it remains challenging to stabilize carbon in the one-dimensional form because of the difficulty of suitably saturating the dangling bonds of carbon. Here, we show through first-principles calculations that ordered polymeric carbon chains can be stabilized in solid Li(2)C(2) under moderate pressure. This pressure-induced phase (above 5 GPa) consists of parallel arrays of twofold zigzag carbon chains embedded in lithium cages, which display a metallic character due to the formation of partially occupied carbon lone-pair states in sp(2)-like hybrids. It is found that this phase remains the most favorable one in a wide range of pressures. At extreme pressure (larger than 215 GPa) a structural and electronic phase transition towards an insulating single-bonded threefold-coordinated carbon network is predicted.

Calmodulin-dependent kinase II mediates vascular smooth muscle cell proliferation and is potentiated by extracellular signal regulated kinase

Vascular smooth muscle cell (VSMC) proliferation contributes to vascular remodeling in atherosclerosis and hypertension. Calcium-dependent signaling through calcium/calmodulin-dependent kinase II (CaMKII) and ERK1/2 activation plays an important role in the regulation of VSMC proliferation by agents such as alpha-adrenergic receptor agonists. Nevertheless, how the CaMKII and ERK pathways interact in VSMCs has yet to be characterized. The aim of the present study was to clarify this interaction in response to alpha(1)-adrenergic receptor-mediated VSMC proliferation. We discovered that phenylephrine stimulation resulted in complex formation between CaMKII and ERK in a manner that facilitated phosphorylation of both protein kinases. To assess the effects of CaMKII/ERK association on VSMC proliferation, we inhibited endogenous CaMKII either pharmacologically or by adenoviral-mediated gene transfer of a kinase-inactive CaMKII mutant. Inhibition of CaMKII activation but not CaMKII autonomous activity significantly decreased formation of the CaMKII/ERK complex. On the contrary, the expression of constitutively active CaMKII enhanced VSMC growth and CaMKII/ERK association. In addressing the mechanism of this effect, we found that CaMKII could not directly phosphorylate ERK but instead enhanced Raf1 activation. By contrast, ERK interaction with CaMKII facilitated CaMKII phosphorylation and promoted its nuclear localization. Our results reveal a critical role for CaMKII in VSMC proliferation and imply that CaMKII facilitates assembly of the Raf/MEK/ERK complex and that ERK enhances CaMKII activation and influences its subcellular localization.

Polaronic hole trapping in doped BaBiO3

The present ab initio study shows that in BaBiO3, Bi3+ sites can trap two holes from the valence band to form Bi5+ cations. The trapping is accompanied by large local lattice distortions; therefore the composite particle consisting of the electronic hole and the local lattice phonon field forms a polaron. Our study clearly shows that even sp elements can trap carriers at lattice sites, if local lattice relaxations are sufficiently large to screen the localized hole. The derived model describes all relevant experimental results, and settles the issue of why hole-doped BaBiO3 remains semiconducting upon moderate hole doping.

Two-dimensional manganese oxide nanolayers on Pd(100): the surface phase diagram

Two-dimensional manganese oxide layers have been grown on Pd(100) and have been characterized by means of scanning tunnelling microscopy, low energy electron diffraction and x-ray photoelectron spectroscopy (XPS). The complex surface phase diagram of MnO(x) on Pd(100) is reported, where nine different novel Mn oxide phases have been detected as a function of the chemical potential of oxygen μ(O). Three regions of the chemical potential of oxygen can be identified, in which structurally related oxide phases are formed, often in coexistence at the surface. The different regions of μ(O) are reflected in the oxidation states of the respective Mn oxide nanolayers as revealed by the Mn 2p and O 1s XPS binding energies. The MnO(x) nanolayers form two-dimensional wetting layers and it is speculated that they mediate the epitaxial growth of MnO on Pd(100) by providing structurally graded interfaces.

Evaluation of the pharmacological activity of the major mexiletine metabolites on skeletal muscle sodium currents

BACKGROUND AND PURPOSE

Mexiletine (Mex), an orally effective antiarrhythmic agent used to treat ventricular arrhythmias, has also been found to be effective for myotonia and neuropathic pain. It is extensively metabolized in humans but little information exists about the pharmacodynamic properties of its metabolites.

EXPERIMENTAL APPROACH

To determine their contribution to the clinical activity of Mex, p-hydroxy-mexiletine (PHM), hydroxy-methyl-mexiletine (HMM), N-hydroxy-mexiletine (NHM) (phase I reaction products) and N-carbonyloxy beta-D-glucuronide (NMG) (phase II reaction product) were tested on sodium currents (I(Na)) of frog skeletal muscle fibres. Sodium currents were elicited with depolarizing pulses from different holding potentials (HP=-140, -100, -70 mV) and stimulation frequencies (0.25, 0.5, 1, 2, 5, 10 Hz) using the vaseline-gap voltage-clamp method.

KEY RESULTS

All the hydroxylated derivatives blocked the sodium channel in a voltage- and use-dependent manner. The PHM, HMM and NHM metabolites were up to 10-fold less effective than the parent compound. However, HMM showed a greater use-dependent behaviour (10 Hz), compared to Mex and the other metabolites. Similar to Mex, these products behaved as inactivating channel blockers. Conjugation with glucuronic acid (NMG) resulted in almost complete abolition of the pharmacological activity of the parent compound.

CONCLUSIONS AND IMPLICATIONS

Thus, although less potent, the phase I metabolites tested demonstrated similar pharmacological behaviour to Mex and might contribute to its clinical profile.

Superconductivity in lithium, potassium, and aluminum under extreme pressure: a first-principles study

Extreme pressure strongly affects the superconducting properties of "simple" elemental metals, such as Li, K, and Al. Pressure induces superconductivity in Li (as high as 17 K) while suppressing it in Al. We report first-principles investigations of the superconducting properties of dense Li, K, and Al based on a recently proposed, parameter-free, method. Our results show an unprecedented agreement with experiments, assess the predictive power of the method over a wide range of densities and electron-phonon couplings, and provide predictions for K, where no experiments exist so far. More importantly, our results help uncover the physics of the different behaviors of Li and Al in terms of phonon softening and Fermi surface nesting in Li.

Superconducting properties of MgB2 from first principles

Solid MgB(2) has rather interesting and technologically important properties, such as a very high superconducting transition temperature. Focusing on this compound, we report the first nontrivial application of a novel density-functional-type theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, we obtain the transition temperature, the gaps, and the specific heat of MgB(2) in very good agreement with experiment. Moreover, our calculations show how the Coulomb interaction acts differently on sigma and pi states, thereby stabilizing the observed superconducting phase.

Synthesis of new 2,6-prolylxylidide analogues of tocainide as stereoselective blockers of voltage-gated Na(+) channels with increased potency and improved use-dependent activity

A series of tocainide chiral analogues were designed, synthesized, and evaluated in vitro, in pure enantiomeric form, as use-dependent blockers of skeletal muscle sodium channels to better understand the structural requirements responsible for the antimyotonic activity. The voltage clamp recordings showed a remarkable increase of both potency and use-dependent behavior with the analogue N-(2, 6-dimethylphenyl)-2-pyrrolidinecarboxamide (1a). In fact (R)-1a was 5-fold more potent than (R)-tocainide in producing the tonic block, i.e., the reduction of peak sodium current in resting conditions after application of the compound, but it was 21-fold more potent in condition of high frequency of stimulation (phasic block). Furthermore, as opposite to tocainide, this compound was also stereoselective, (S)-1a being 2-3-fold less potent than (R)-1a. The introduction in 1a of a methyl group in place of the hydrogen bonded to either the aminic nitrogen atom [N-(2, 6-dimethylphenyl)-1-methyl-2-pyrrolidinecarboxamide (2a)] or the amidic nitrogen atom [N-(2, 6-dimethylphenyl)-N-methyl-2-pyrrolidinecarboxamide (3a)] led unexpectedly to an inversion of stereoselectivity, the (S)-enantiomers being 3-fold more potent than the (R)-ones. The comparison between eutomers showed that (S)-2a and (S)-3a are almost equieffective to (R)-1a in producing a tonic block, the half-maximal concentrations being about 100 microM; however, the use-dependent behavior was remarkably decreased by the presence of the methyl group: i.e., the gain of potency observed at high frequency of stimulation amounted to 3 and 1.6 times for 2a and 3a, respectively. The replacement of both hydrogens bonded to the aminic and amidic nitrogen atoms resulted in N-(2,6-dimethylphenyl)-N, 1-dimethyl-2-pyrrolidinecarboxamide (4a) in which the (S)-isomer was still twice as potent as the (R)-one, but the absolute potency and mostly the use-dependent behavior were strongly reduced, showing therefore no clear advantages with respect to tocainide. The use-dependent behavior, which plays a pivotal role for antimyotonic activity, is strongly reduced by the presence of methyl groups on the nitrogen atoms, likely for modification of pK(a) and/or for constraint of molecular conformation.

Facile entry to (-)-(R)- and (+)-(S)-mexiletine

The title compounds, 1a and 1b, have been synthesized in a three-step sequence starting from (-)-(S) and (+)-(R)-propylene oxide, respectively, in acceptable overall yields. The enantiomeric excess values for 1a and 1b were 96% and 93% respectively, as assessed by HPLC analysis on a chiral stationary phase of the corresponding N-acetyl derivatives. The synthetic route herein presented may represent a facile entry to highly enriched mexiletine enantiomers, alternative to those previously reported in the literature.

Molecular determinants of mexiletine structure for potent and use-dependent block of skeletal muscle sodium channels

On the basis of the information about drug receptor on voltage-gated sodium channels, mexiletine (Mex) analogs with substitutions at either the asymmetric carbon atom or the aromatic ring were synthesized as pure enantiomers. The compounds were tested in vitro for their ability to produce voltage- and use-dependent block of sodium currents (I(Na)) of frog muscle fibers by the vaseline-gap voltage-clamp method. In all experimental conditions, the drug potency was highly correlated with the lipophilicity of the group on the asymmetric center, the derivative with a benzyl moiety (Me6) having IC(50) values more than 10 times lower than those of Mex, followed by the phenyl (Me4) and the isopropyl (Me5) derivative. All of the compounds showed a further reduction of IC(50) values at depolarized membrane potentials and at high frequency of stimulation (10 Hz). Mex and Me5, but not Me4, produced a stereoselective tonic block of I(Na), the R-(-) isomers being 2-fold more potent than the S-(+) ones. The removal of both methyl groups from the aromatic ring of Mex (Me3) caused a 7-fold reduction of the potency, whereas similar substitutions on the phenyl derivative Me4 (Me7 and Me8) produced opposite effects. In fact, the IC(50) of R-(-) Me7 for use-dependent block of I(Na) was 30 times lower than that of R-(-) Mex. Me8 and Me7 were stereoselective during both tonic and use-dependent blockade. All of the compounds left-shifted the steady-state inactivation curves in relation to their potency and to the duration of the inactivating prepulse. Finally, the presence of apolar groups on the asymmetric center of mexiletine is pivotal to reinforce hydrophobic interactions with the proposed aromatic residues at the receptor, and lead to potent and therapeutically interesting inactivated channel blockers.

Homologation of mexiletine alkyl chain and stereoselective blockade of skeletal muscle sodium channels

The optical isomers (-)-(S)- and (+)-(R)-3-(2, 6-dimethylphenoxy)-2-methyl-1-propanamine (Me2), homologues of the antiarrhythmic and antimyotonic drug mexiletine (Mex), were synthesized and assayed as new potential antimyotonic agents. As observed with Mex, Me2 exhibits an enantioselective behaviour. Tests carried out on sodium currents of single muscle fibres of Rana esculenta demonstrated that (-)-(S)- and (+)-(R)-Me2 were less potent than Mex in producing tonic block, but showed a higher use-dependent block. (-)-(S)-Me2 and (-)-(R)-Mex were also used to study the excitability of muscle fibres of myotonic ADR mice, a phenotype of a recessive form of low G(Cl) myotonia. (-)-(S)-Me2 reduced spontaneous discharges and after discharges better than (-)-(R)-Mex in agreement with the use-dependent block of sodium currents.

Cardiac and humoral changes induced by recreational scuba diving

The aim of this study was to evaluate the prevalence and the possible clinical relevance of circulating bubbles after a recreational scuba dive. Twenty healthy subjects (18 male, 2 female; age range 25-36 yr) underwent a Doppler-echocardiographic study in basal conditions and 1.9+/-0.2 h after a recreational scuba dive. Venous blood samples were taken just before the two ultrasonic studies to obtain leukocyte and platelet counts and plasma activity of angiotensin-converting enzyme (ACE; assumed as pulmonary endothelial damage marker). Circulating bubbles were observed in the right heart chambers of 12 subjects after the dive. The echocardiographic and humoral data were evaluated before and after diving in subjects with and without circulating bubbles. At the postdive evaluation, a significant increase in right ventricular dimensions (37.4+/-3.9 vs. 40.7+/-4.0 mm; P < 0.01) and a significant reduction of early diastolic filling velocities of both right (59.1+/-16.4 vs. 48.9+/-6.9 cm x s-(-1); P < 0.05) and left (76.2+/-9.9 vs. 67.5+/-10.2 cm x s(-1); P < 0.02) ventricle were observed in the group with circulating bubbles. In the same group, significant increases in ACE activity (92.9+/-41.1 vs. 105.9+/-41.7 U x liter(-1); P < 0.05), platelets (217+/-34 vs. 232+/-35 10(3) x microl(-1); P < 0.01), and granulocytes (3,704+/-715 x microl(-1) vs. 5,212+/-1,995 x microl(-1); P < 0.001) were observed. The bubble-free group showed only a postdive significant decrease of left ventricular early diastolic filling velocity (74+/-6.8 vs. 62.6+/-4.5 cm x s(-1); P < 0.005). These data may indicate that circulating gas bubbles are associated with cardiac changes, suggesting a right ventricular overload and an impairment of ventricular diastolic performance. Postdive humoral and hematologic changes are consistent with the hypothesis that "silent" gas bubbles may damage pulmonary endothelium and activate the reactive systems of the human body.

Effects of mexiletine on ATP sensitive K+ channel of rat skeletal muscle fibres: a state dependent mechanism of action

1. The effects of mexiletine were evaluated on the ATP-sensitive K+ channel (K(ATP)) of rat skeletal muscle fibres using patch clamp techniques. The effects of mexiletine were studied on macropatch currents 20 s (maximally activated), 8 min (early stage of rundown) and 15 min (late stage of rundown) after excision in the absence or in the presence of internal ADP (50-100 microM) or UDP (500 microM). In addition, the effects of mexiletine were tested on single channel. 2. In the absence of ADP and UDP, mexiletine inhibited the current through maximally activated channels with an IC50 of -5.58+/-0.3 M. Nucleoside diphosphates shifted the current versus mexiletine concentration relationship to the right on the log concentration axis. UDP (500 microM) was more efficacious than ADP (50-100 microM) in this effect. 3. At the early stage of rundown, the sensitivity of the channel to mexiletine was reduced and nucleoside diphosphates, particularly UDP, antagonized the effect of mexiletine. At the late stage of rundown, mexiletine did not affect the currents. 4. At the single channel level, 1 microM mexiletine reduced the mean burst duration by 63% and prolonged the arithmetic mean closed time intervals between the bursts of openings without altering the open time and closed time distributions. Mexiletine did not affect the single channel conductance. 5. These results show that in skeletal muscle, mexiletine is a state-dependent K(ATP) channel inhibitor which either acts through the nucleotide binding site or a site allosterically coupled to it.

Inhibition of frog skeletal muscle sodium channels by newly synthesized chiral derivatives of mexiletine and tocainide

To search for potent use-dependent blockers of skeletal muscle sodium channels as potential antimyotonic agents, the actions of newly synthesized chiral analogs of mexiletine and tocainide were tested in vitro on sodium currents of single fibers of frog semitendinosus muscle by vaseline-gap voltage clamp method. The effect of each drug on the maximal peak Na+ transient (I(Na) max) was evaluated as both tonic and use-dependent block by using infrequent depolarizing stimulation and trains of pulses at 2-10 Hz frequency, respectively. The mexiletine analog 3-(2,6-dimethylphenoxy)-2-methylpropanamine (Me2), having an increased distance between the phenyl and the amino groups, was less potent than mexiletine in producing a tonic block but produced a remarkable use-dependent block. In fact, the half-maximal concentration (IC50) for tonic block of S(-)-Me2 was 108 microM vs. 54.5 microM of R(-)-mexiletine, but the IC50 was 6.2 times lowered by the 10 Hz stimulation with respect to the 2.4 fold decrease observed with mexiletine. The R(-)-mexiletine and the S(-)-Me2 were about twofold more potent than the corresponding enantiomers in producing a tonic block, but the stereoselectivity attenuated during use-dependent blockade. The more lipophilic 2-(4-chloro-2-methylphenoxy)-1-phenylethylamine (Me1), presently available as raceme, produced a potent and irreversible tonic block of the sodium currents with an IC50 of 29 microM, but had a less pronounced use-dependent inhibition, with a 1.9 fold decrease of the IC50 at 10 Hz. The R(-) isomer of 2',6'-valinoxylidide (To1), a tocainide derivative with an increased hindrance on the chiral carbon atom, was twofold (IC50 = 209 microM) and tenfold (IC50 = 27.4 microM) more potent than R(-)-tocainide in tonic and use-dependent block, respectively. Tocainide was almost devoid of stereoselectivity, whereas the eudismic ratio of To1 [(IC50 S(+)-To1/IC50 R(-)-To1] was 1.7. As for mexiletine and Me2, the stereoselectivity of To1 was the weaker the higher the frequency of stimulation. The cyclic pyrrolo-imidazolonic tocainide analog To2 produced a small tonic block at 500 microM, and 1 min stimulation at 10 Hz was needed to show up a 50% block of I(Na) max. All the compounds produced a left-shift of the steady-state inactivation curve correlated positively with the extent of use-dependent inhibition, with the exception of the cyclic To2 that acted as an open-channel blocker. The highly use-dependent blockers Me2 and To1 might be promising drugs to solve high frequency discharges of action potentials typical of myotonic muscles. Concomitantly the high potency of Me1 and the open-channel block exerted by To2 can represent important features to get selective blockers for skeletal muscle sodium channels.

Evaluation of the antimyotonic activity of mexiletine and some new analogs on sodium currents of single muscle fibers and on the abnormal excitability of the myotonic ADR mouse

To search for use-dependent sodium channel blockers to selectively solve skeletal muscle hyperexcitability in hereditary myotonias, mexiletine (MEX; compound I) and its newly synthetized analogs, 2-(4-chloro-2-methylphenoxy)-benzenethanamine (compound II) and (-)-S-3-(2,6-dimethylphenoxy)-2-methylpropanamine (compound III), were tested on intercostal muscle fibers from the myotonic ADR mouse through use of the standard current-clamp microelectrode technique. In parallel, the effects of these compounds on the sodium channels were measured on frog muscle fibers under voltage-clamp conditions. The tonic and use-dependent blocks of peak sodium currents (I(Namax)) produced by each compound were evaluated by using a single depolarizing pulse and a pulse train at 10 Hz frequency, respectively. At 10 and 50 microM, MEX decreased the occurrence of spontaneous excitability in myotonic muscle fibers; 100 microM was required to decrease the amplitude of the action potential and the stimulus-induced firing of the membrane as well as to increase the threshold for generation of action potential. At 300 microM, MEX decreased the latency of the action potential and increased the threshold current to elicit a single action potential. MEX produced a tonic block of I(Namax) with an half-maximal concentration (IC50) of 83 microM, but the IC50 value for use-dependent block was 3-fold lower. Compound III, which differs from MEX in that it has a longer alkyl chain, similarly blocked first the spontaneous and then the stimulus-evoked excitability of myotonic muscle fibers but at 2-fold lower concentrations than MEX. Compound III was less potent than MEX in producing a tonic block of I(Namax) (IC50 = 108 microM) but was a strong use-dependent blocker with an IC50 close to 15 microM. The more lipophylic compound II irreversibly blocked both spontaneous and stimulus-evoked membrane excitability at concentrations as low as 10 microM and shortened the latency of the action potential in a concentration-dependent fashion. Compound II produced a potent tonic block of I(Namax) (IC50 = 30 microM), and its potency increased 2-fold during high-frequency stimulation. Both of the new analogs (compound II in particular), but not MEX, were less effective on the excitability parameters of striated fibers of healthy vs. ADR mice, a characteristic that increases their interest as potential antimyotonic agents.

Penetration of vancomycin into human lung tissue

Vancomycin penetration into lung tissue was evaluated in thirty patients following the administration of 1 g of vancomycin as a 1 h i.v. infusion. Mean concentrations (range) of vancomycin in lung tissue were 9.6 (6.3-12.1) mg/kg at 1h, 5.7 (4.7-7.4) mg/kg at 2 h, 4.2 (0.8-6.5) mg/kg at 3-4 h, 2.4 (1.4-4.7) mg/kg at 6 h, and 2.8 (0.9-7.8) mg/kg at 12 h after the end of infusion. Ratios of lung tissue to serum concentration ranged 0.24 to 0.41 at 1 and 12 h, respectively. One of six patients observed at 6 h, and 3 of 7 patients at 12 h did not have detectable levels of vancomycin in lung tissue. A 1 h iv infusion of a 1 g dose of vancomycin does not achieve sustained lung concentrations above the MIC for susceptible staphylococci over a dosing interval of 12 h. Therefore, a more appropriate modality of administration, such as continuous infusion, should be considered.

Stereoselective effects of mexiletine enantiomers on sodium currents and excitability characteristics of adult skeletal muscle fibers

The effects of the enantiomers of mexiletine were tested on sodium currents of frog skeletal muscle fibers recorded by means of the three vaseline gap voltage clamp method and compared with the effects produced by tocainide enantiomers. The R-(-) mexiletine produced a tonic block of the sodium current, elicited by single depolarizing test pulses from the holding potential of -100 mV to -20 mV, with an IC50 of 43.9 +/- 1 microM, whereas the corresponding S-(+) enantiomer produced the same effects at about twofold higher concentrations. A similar steroselectivity was observed with tocainide enantiomers, but at about 5 fold higher concentrations. Both the R-(-) and S-(+) enantiomers of mexiletine and tocainide produced a further use-dependent block of sodium currents when the test pulse was applied repetitively at a frequency of 2 Hz. The use dependent behavior led to a significant lowering of the IC50 values with respect to the tonic block but the eudismic ratios ([IC50S-(+)]/[IC50R(-)]) and the relative potency between mexiletine and tocainide were maintained. All the tested compounds produced a left shift of the steady state inactivation curves (h infinity), suggesting a high-affinity interaction with the inactivated sodium channels. Again a stronger potency of R-(-) vs. S-(+) enantiomers and of mexiletine vs. tocainide was observed. The excitability characteristics recorded from the semitendinosus muscle by the two microelectrode technique were modified by the tested drugs in agreement with their ability to block sodium current. Thus a concentration-related increase in the threshold current required to elicit an action potential as observed along with a decrease in the amplitude and a shortening of the latency of action potential and a decrease in the firing capability of the membrane. Again the R-(-) isomers were more potent than the S-(+) ones and mexiletine was more effective than tocainide. These data corroborate the presence of a stereospecific site for these drugs on adult skeletal muscle sodium channels. The constant eudismic ratios between the enantiomers during both tonic and use-dependent block suggest that the increase in the apparent affinity of the receptor during state-dependent conformational changes of the channel does not enhance its stereospecificity. The decrease in effective concentration upon high frequency stimulation supports the potential usefulness of low doses of R-(-) mexiletine in the treatment of the abnormal hyperexcitability of the myotonic muscles, with a likely reduction of unwanted side effects.

Rapid sensory remapping in the adult human brain as inferred from phantom breast perception

We provide evidence for a perceptual marker of neuroplasticity in female mastectomy patients who reported phantom breast perceptions. When tactile stimuli were delivered to dorso-thoracic, shoulder and pinna regions ipsilateral to the mastectomy, these patients (in some cases even 5 days after the operation) referred the stimuli to the amputated breast mainly to the nipple. The somatosensory representation of the stimulated regions is probably adjacent to the former representation of the amputated breast. These results suggest that input from stimulated regions of the skin can drive neurones originally driven by input from the amputated breast. The apparent functional relation between pinna and nipple might give clues to the mechanisms underlying referred sensations and pain.

Stereoselectivity in central analgesic action of tocainide and its analogs

The antiarrhythmic drug tocainide (5a) and some related chiral alpha-amino and alpha-imino anilides (5b-e) were synthesized in optically active form. The antinociceptive effects of the different stereoisomers of these compounds were examined and it was found that the analgesic effect of tocainide is due only to its (-)-(R)-enantiomer. Benzyl replacement for methyl group at the stereogenic centre of tocainide causes loss of activity while both enantiomers of the alpha-iminoxilidide 5e and of the strictly related tocainide analog 5d produce an analgesic effect without any stereoselectivity. Pharmacological tests and [3H] quinuclidinyl benzilate ([3H]QNB) binding assay, taken together, seem to show that the antinociceptive effect of (-)-(R)-tocainide, like the analgesia induced by lidocaine, procaine, and mexiletine, is due to a central presynaptic cholinergic mechanism of action.

Stereoselective interaction of tocainide and its chiral analogs with the sodium channels in human myoballs

The effects of both enantiomers of tocainide and of some of its chiral analogs on the inactivation of the sodium current in human myoballs were investigated with the whole-cell recording technique. Structure and electron densities of the applied compounds were calculated and compared to the results. Both the R(-) and the S(+) enantiomers had little effect on fast inactivation determined with short prepulses according to Hodgkin and Huxley (1952; h infinity curve). When the inactivating prepulses used in this pulse protocol were prolonged to 1024 ms, both tocainide enantiomers increased inactivation severely, suggesting that the drug binds to the channel when it is in the state of intermediate inactivation (Fakler et al. 1990). Tetrodotoxin-resistant "juvenile" sodium channels were more affected than tetrodotoxin-sensitive "adult" channels. The R form was four times as effective as the S form. The compound obtained by substitution of the methyl group on the chiral centre of tocainide with a benzyl group, although in the less potent S form, affected inactivation of the juvenile sodium channels much more than the potent (R)-tocainide. Two additional substitutions, performed on the aromatic ring of tocainide, gave a compound that was most potent in shifting the inactivation curves, but without any selectivity for juvenile or adult channels.

[Studies on the chiroptical properties of 2,4-dinitrophenyl derivatives of amino compounds of pharmaceutical interest]

Some results on the chiroptical properties of 2,4-dinitrophenylaminoacids reported in the literature, have been re-examined since they were in disagreement with our earlier research. Extension of this research to several sympathomimetic amines, demonstrates that the chiroptical properties of these derivatives show coherent behaviour; as a consequence the absolute configuration of the amino compounds condensed with Sanger reagent can be correlated to the sign of their higher wavelength Cotton effect.

[Determination of absolute configuration of amine compounds of pharmaceutical interest by means of measurement of circular dichroism]

The CD curves study of the pyridyl-N-oxide derivatives of some adrenergic and anorexigenic amines showed that the sign of the Cotton effect can be related to their absolute configuration. The obtained results confirm the absolute configuration of fenfluramine and nor-fenfluramine and suggest that the levo isomer of ortoxine has R-configuration.