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Biomedical subjects

M Mayor

Publications and source records attributed to M Mayor.

At least 19 recordsLinked to original sources
PubMed2006

Two-dimensional assembly and local redox-activity of molecular hybrid structures in an electrochemical environment.

The self-assembly and redox-properties of two viologen derivatives, N-hexyl-N'-(6-thiohexyl)-4,4'-bipyridinium bromide (HS-6V6-H) and N,N'-bis(6-thiohexyl)-4,4'-bipyridinium bromide (HS-6V6-SH), immobilized on Au(lll)-(1 x 1) macro-electrodes were investigated by cyclic voltammetry, surface enhanced infrared spectroscopy (SEIRAS) and in situ scanning tunneling microscopy (STM). Depending on the assembly conditions one could distinguish three different types of adlayers for both viologens: a low coverage disordered and an ordered "striped" phase of flat oriented molecules as well as a high coverage monolayer composed of tilted viologen moieties. Both molecules, HS-6V6-H and HS-6V6-SH, were successfully immobilized on Au(poly) nano-electrodes, which gave a well-defined redox-response in the lower pA-current range. An in situ STM configuration was employed to explore electron transport properties of single molecule junctions Au(T)/HS-6V6-SH(HS-6V6-H)/Au(S). The observed sigmoidal potential dependence, measured at variable substrate potential E(S) and at constant bias voltage (E(T) - E(S)), was attributed to electronic structure changes of the viologen moiety during the one-electron reduction/re-oxidation process V2+ < -- > V+*. Tunneling experiments in asymmetric, STM-based junctions Au(T)-S-6V6-H/Au(S) revealed current (i(T))-voltage (E(T)) curves with a maximum located at the equilibrium potential of the redox-process V2+ < -- > V+*. The experimental i(T)--E(T) characteristics of the HS-6V6-H-modified tunneling junction were tentatively attributed to a sequential two-step electron transfer mechanism.

Journal Article↗
PubMed2005

Natural history of Hymenoptera venom allergy in Eastern Spain.

INTRODUCTION: The natural history of stings, the clinical reaction of the patient and in vivo and in vitro tests are necessary parameters to assess before initiating Hymenoptera venom immunotherapy. In the decision to initiate immunotherapy with Hymenoptera venom, it is not usual to evaluate the natural history of the disease, which seems to be self-limiting and therefore of variable clinical significance. OBJECTIVES: Our aim was to determine the natural history of Hymenoptera hypersensitivity over 4 consecutive years in a rural Mediterranean population. METHODS: An epidemiological study of Hymenoptera sting reactions and possible sensitivity was carried out in 145 randomly selected subjects out of a rural Mediterranean population of 600. Seventy-two subjects, including those with a history of anaphylaxis, completed the 4-year study. The nature of their clinical reactions, age, sex, history of atopy, profession, family history of reactions to Hymenoptera insects, time elapsed since the last sting, number of stings and specific IgE and IgG were determined (the latter, to the three most important insects in the area: Apis mellifera, Polistes dominulus, and Vespula germanica). RESULTS: Of the 72 subjects, four subjects had systemic reactions (SR), 23 had large local reaction (LLR) and all the others (117) was minor local reactions. None who had experienced an SR had a repeat SR when re-stung over the 4-year study. Of those with LLR, 12 subjects had the same type of reaction and 11 experienced more mild local reactions when re-stung. In the SR and local reaction groups, IgE to honey bee (Hb) increased significantly during the study period, whereas in those with only LLR, specific IgE to wasp (Polistes) decreased. Specific IgG to Polistes and Vespula (wasps) decreased significantly, whereas there was no change in the specific IgG to Hb in any of the groups. The number of stings per year decreased at the end of the study in all groups, but positive-specific IgG was higher in subjects with the greatest number of stings. On multivariate analysis using logistic regression, the existence of specific IgE to bee venom, male sex, being an agricultural worker, age of over 16 years and more than five stings per year are seen as individual or co-factors for developing SR or LLR. CONCLUSIONS: The prevalence of SR was 2.8% in our Mediterranean population. The evolution of IgE and IgG throughout the 4-year study differed depending on the Hymenoptera studied. Adult male agricultural workers are at greater risk of having SR or LLR, especially when they have specific IgE to Hb and suffer from more than five stings every 4 years.

Adult↗
PubMed2003

An extended upper atmosphere around the extrasolar planet HD209458b.

The planet in the system HD209458 is the first one for which repeated transits across the stellar disk have been observed. Together with radial velocity measurements, this has led to a determination of the planet's radius and mass, confirming it to be a gas giant. But despite numerous searches for an atmospheric signature, only the dense lower atmosphere of HD209458b has been observed, through the detection of neutral sodium absorption. Here we report the detection of atomic hydrogen absorption in the stellar Lyman alpha line during three transits of HD209458b. An absorption of 15 +/- 4% (1sigma) is observed. Comparison with models shows that this absorption should take place beyond the Roche limit and therefore can be understood in terms of escaping hydrogen atoms.

Atmosphere↗
PubMed2003

Postmenopausal frontal fibrosing alopecia.

Recently a new entity, postmenopausal frontal fibrosing alopecia, was added to the established subtypes of scarring alopecias affecting postmenopausal women. This condition is characterized by a progressive frontal hairline recession associated with scarring. We studied the clinical and histopathologic features in four women with this disorder. Of note, a history of bilateral oophorectomy in two of them appears to be a new association. All four cases had frontoparietal recession of the hairline and two of them also had loss of their eyebrows. None of our four patients had any mucous membrane or other skin lesions. Histological examination showed perifollicular fibrosis and lymphocytic inflammation around the isthmus and infundibular areas of the follicles. No effective treatments have emerged for this type of postmenopausal alopecia, but progression of the hair loss and scarring appears to be self-limiting. We believe that this condition is a distinct clinicopathological variant of lichen planopilaris.

Adult↗
PubMed2002

Driving current through single organic molecules.

We investigate electronic transport through two types of conjugated molecules. Mechanically controlled break junctions are used to couple thiol end groups of single molecules to two gold electrodes. Current-voltage characteristics ( IVs) of the metal-molecule-metal system are observed. These IVs reproduce the spatial symmetry of the molecules with respect to the direction of current flow. We hereby unambiguously detect an intrinsic property of the molecule and are able to distinguish the influence of both the molecule and the contact to the metal electrodes on the transport properties of the compound system.

Journal Article↗
PubMed2002

Electron transfer through bridging molecular structures.

Pairs of reducible pentakis(thiophenyl)benzene subunits are linked by different molecular structures as model compounds for reducible molecular-wire-type synthons showing varying electron-transfer ability as a function of the bridging structures, consisting of either para-divinylbenzene, bis-hydrazone, or diacetylene. Their electron-transfer ability from one reducible subunit to the other was investigated by electrochemical and spectroelectrochemical methods. In the case of the bis-hydrazone bridge and the diacetylene bridge, the solid-state structures support the experimental findings. While the para-divinylbenzene bridge completely isolates the reducible subunits (class I system) the diacetylene bridge electronically connects the two reducible structures (class III system), demonstrating its potential application as a "molecular wire." The bis-hydrazone linked dimer displays electronic communication only to a small extend, which was only observed in the spectroelectrochemical investigation. The diacetylene connection as active electron-transfer linker together with poly(thiophenyl)benzene as reducible subunits was used to design more complex molecular architectures. Linear rodlike structures did allow adjustment of the length of these type of molecular wires and investigation of the extent of electron mobility. Cyclic structures addressed the possibility of moving electrons on a bent molecular wire.

Benzene↗
PubMed2001

Evidence for planet engulfment by the star HD82943.

Current models of the evolution of the known extrasolar planetary systems need to incorporate orbital migration and/or gravitational interactions among giant planets to explain the presence of large bodies close to their parent stars. These processes could also lead to planets being ingested by their parent stars, which would alter the relative abundances of elements heavier than helium in the stellar atmospheres. In particular, the abundance of the rare 6Li isotope, which is normally destroyed in the early evolution of solar-type stars but preserved intact in the atmospheres of giant planets, would be boosted substantially. 6Li has not hitherto been observed reliably in a metal-rich star, where metallicity refers to the total abundance of elements heavier than helium. Here we report the discovery of 6Li in the atmosphere of the metal-rich solar-type star HD82943, which is known to have an orbiting giant planet. The presence of 6Li can probably be interpreted as evidence for a planet (or planets) having been engulfed by the parent star.

Journal Article↗
PubMed2001

Electron transfer through molecular bridges between reducible pentakis(thiophenyl)benzene subunits.

"Dimers" 3, 4 and 7, which consist of two reducible pentakis(thiophenyl)benzene subunits linked by different molecular structures, have been synthesised as model compounds for reducible molecular-wire-type synthons to represent differences in the electron-transfer ability as a function of the bridging structure. The bridging units consist of para-divinylbenzene in 3, bis-hydrazone in 4 and diacetylene in 7. Their ability to transfer electrons from one reducible subunit to the other was investigated by electrochemical and spectroelectrochemical methods and, in the case of 4 and 7, the solid-state structures support the experimental findings. The para-divinylbenzene bridge in 3 was found to completely isolate the reducible structures (Class I system). In contrast, the diacetylene bridge in 7 electronically connects the two reducible structures (Class III system) and, thus, demonstrates its potential application as a "molecular wire". The bis-hydrazone-linked compound 4 displayed only a low level of electronic connection between the subunits and was only observed in the spectroelectrochemical investigation.

Journal Article↗
PubMed2000

The Spectroscopic Orbit of the Planetary Companion Transiting HD 209458.

We report a spectroscopic orbit with period P=3.52433+/-0.00027 days for the planetary companion that transits the solar-type star HD 209458. For the metallicity, mass, and radius of the star, we derive [Fe/H&sqbr0;=0.00+/-0.02, M*=1.1+/-0.1 M middle dot in circle, and R*=1.2+/-0.1 R middle dot in circle. This is based on a new analysis of the iron lines in our HIRES template spectrum and also on the absolute magnitude, effective temperature, and color of the star, and it uses isochrones from four different sets of stellar evolution models. Using these values for the stellar parameters, we reanalyze the transit data and derive an orbital inclination of i=86&fdg;1+/-1&fdg;6. For the planet, we derive a mass of Mp=0.69+/-0.05 MJup, a radius of Rp=1.40+/-0.17 RJup, and a density of rho=0.31+/-0.07 g cm-3.

Journal Article↗
PubMed2000

Detection of Planetary Transits Across a Sun-like Star.

We report high-precision, high-cadence photometric measurements of the star HD 209458, which is known from radial velocity measurements to have a planetary-mass companion in a close orbit. We detect two separate transit events at times that are consistent with the radial velocity measurements. In both cases, the detailed shape of the transit curve due to both the limb darkening of the star and the finite size of the planet is clearly evident. Assuming stellar parameters of 1.1 R middle dot in circle and 1.1 M middle dot in circle, we find that the data are best interpreted as a gas giant with a radius of 1.27+/-0.02 RJup in an orbit with an inclination of 87&fdg;1+/-0&fdg;2. We present values for the planetary surface gravity, escape velocity, and average density and discuss the numerous observations that are warranted now that a planet is known to transit the disk of its parent star.

Journal Article↗
PubMed2000

Mondor's disease.

BACKGROUND: Mondor's disease is a rare entity characterized by thrombophlebitis of the subcutaneous veins of the anterolateral thoraco-abdominal wall. The most common clinical manifestations are a painful subcutaneous cord, sensation of tension, and skin retraction. This condition is usually a benign and self-limited process, although it has been associated with breast cancer. METHODS: We describe four new cases, two men and two women, and comment on the clinical signs and possible etiopathogenic features. General physical examination, radiologic and ecographic studies, laboratory analysis including tumor markers, and exhaustive coagulation study were carried out on all patients. RESULTS: No cases were associated with malignant disease and/or hypercoagulability stage. With conservative treatment, the evolution proved favorable in all patients. CONCLUSIONS: Mondor's disease is usually a benign and self-limited process, but we recommend laboratory studies and physical examination, including mammography in women, in order to rule out the presence of systemic disorders, especially breast cancer.

Abdominal Muscles↗
PubMed2000

Ibogaine: complex pharmacokinetics, concerns for safety, and preliminary efficacy measures.

Ibogaine is an indole alkaloid found in the roots of Tabernanthe Iboga (Apocynaceae family), a rain forest shrub that is native to western Africa. Ibogaine is used by indigenous peoples in low doses to combat fatigue, hunger and thirst, and in higher doses as a sacrament in religious rituals. Members of American and European addict self-help groups have claimed that ibogaine promotes long-term drug abstinence from addictive substances, including psychostimulants and opiates. Anecdotal reports attest that a single dose of ibogaine eliminates opiate withdrawal symptoms and reduces drug craving for extended periods of time. The purported efficacy of ibogaine for the treatment of drug dependence may be due in part to an active metabolite. The majority of ibogaine biotransformation proceeds via CYP2D6, including the O-demethylation of ibogaine to 12-hydroxyibogamine (noribogaine). Blood concentration-time effect profiles of ibogaine and noribogaine obtained for individual subjects after single oral dose administrations demonstrate complex pharmacokinetic profiles. Ibogaine has shown preliminary efficacy for opiate detoxification and for short-term stabilization of drug-dependent persons as they prepare to enter substance abuse treatment. We report here that ibogaine significantly decreased craving for cocaine and heroin during inpatient detoxification. Self-reports of depressive symptoms were also significantly lower after ibogaine treatment and at 30 days after program discharge. Because ibogaine is cleared rapidly from the blood, the beneficial aftereffects of the drug on craving and depressed mood may be related to the effects of noribogaine on the central nervous system.

Adult↗
PubMed2000

Physician attitudes toward palliative care at a community teaching hospital.

The goals of the study were to explore physicians' attitudes and opinions about palliative care and its implementation. Four focus groups composed of attending physicians were conducted by a professional facilitator at a community teaching hospital. The audio-tapes of the groups were carefully transcribed and analyzed according to rigorous qualitative methodology. Physicians perceived palliative care and pain control as important. Problems they perceived were a lack of education for physicians, residents, other health care professionals, and the general public; a lack of hospital support systems to implement palliative care appropriately, and a lack of knowledge and support regarding legal considerations. They believed that a palliative care unit was a reasonable tool to overcome many obstacles to good end-of-life care.

Attitude of Health Personnel↗