Brachymetatarsia

Brachymetatarsia involves a reduction in length of one or more metatarsals. The affected metatarsal is shortened by 5 mm or more, altering the normal metatarsal parabola. In addition to being an aesthetic deformity, it can present with pain due to transfer metatarsalgia. A possible association with genetic disorders needs to be investigated during clinical evaluation. Surgical treatment may involve a one-stage lengthening procedure or progressive distraction, each having its advantages and limitations.

Analysis of alternariol and alternariol monomethyl ether in foodstuffs by molecularly imprinted solid-phase extraction and ultra-high-performance liquid chromatography tandem mass spectrometry

Molecularly imprinted porous polymer microspheres selective to Alternaria mycotoxins, alternariol (AOH) and alternariol monomethyl ether (AME), were synthesized and applied to the extraction of both mycotoxins in food samples. The polymer was prepared using 4-vinylpiridine (VIPY) and methacrylamide (MAM) as functional monomers, ethylene glycol dimethacrylate (EDMA) as cross-linker and 3,8,9-trihydroxy-6H-dibenzo[b,d]pyran-6-one (S2) as AOH surrogate template. A molecularly imprinted solid phase extraction (MISPE) method has been optimized for the selective isolation of the mycotoxins from aqueous samples coupled to HPLC with fluorescence (λ_ex=258nm; λ_em=440nm) or MS/MS analysis. The MISPE method was validated by UPLC-MS/MS for the determination of AOH and AME in tomato juice and sesame oil based on the European Commission Decision 2002/657/EC. Method performance was satisfactory with recoveries from 92.5% to 106.2% and limits of quantification within the 1.1-2.8µgkg^-1 range in both samples.

High resolution mass spectrometry-based screening reveals lipophilic toxins in multiple trophic levels from the North Sea

Lipophilic marine biotoxins, which are mainly produced by small dinoflagellates, are increasingly detected in coastal waters across the globe. As these producers are consumed by zooplankton and shellfish, the toxins are introduced, bioaccumulated and possibly biomagnified throughout marine food chains. Recent research has demonstrated that ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) is an excellent tool to detect marine toxins in algae and seafood. In this study, UHPLC-HRMS was used to screen lipophilic marine biotoxins in organisms from different trophic levels of the Belgian coastal zone ecosystem. A total of 20 tentatively identified lipophilic compounds was detected. Hereby, the trophic transfer of lipophilic marine biotoxins to the upper trophic level was considered to be rather limited. Furthermore, 36% of the compounds was clearly transferred between different organisms. A significant biotransformation of compounds from the okadaic acid and spirolide toxin groups was observed (64%), mainly in filter feeders. Through a multi-targeted approach, this study showed that marine organisms in the Belgian coastal zone are exposed to a multi-toxin mixture. Further research on both single compound and interactive toxic effects of the frequently detected lipophilic marine toxin ester metabolites throughout the food chain is therefore needed. As a future perspective, confirmatory identification of potential toxins by studying their fragmentation spectra (using new tools such as hybrid quadrupole Q-Exactive™ Orbitrap-MS) is designated.

A balanced sleep/wakefulness classification method based on actigraphic data in adolescents

Several research groups have developed automated sleep-wakefulness classifiers for night wrist actigraphic (ACT) data. These classifiers tend to be unbalanced, with a tendency to overestimate the detection of sleep, at the expense of poorer detection of wakefulness. The reason for this is that the measure of success in previous works was the maximization of the overall accuracy, disregarding the balance between sensitivity and specificity. The databases were usually sleep recordings, hence the over-representation of sleep samples. In this work an Artificial Neural Network (ANN), sleep-wakefulness classifier is presented. ACT data was collected every minute. An 11-min moving window was used as observing frame for data analysis, as applied in previous sleep ACT studies. However, our feature set adds new variables such as the time of the day, the median and the median absolute deviation. Sleep and Wakefulness data were balanced to improve the system training. A comparison with previous studies can still be done, by choosing the point in the ROC curve associated with the corresponding data balance. Our results are compared with a polysomnogram-based hypnogram as golden standard, rendering an accuracy of 92.8%, a sensitivity of 97.6% and a specificity of 73.4%. Geometric mean between sensitivity and specificity is 84.9%.

Molecular recognition with nanostructures fabricated by photopolymerization within metallic subwavelength apertures

The first demonstration of fabrication of submicron lateral resolution molecularly imprinted polymer (MIP) patterns by photoinduced local polymerization within metal subwavelength apertures is reported. The size of the photopolymerized MIP features is finely tuned by the dose of 532 nm radiation. Rhodamine 123 (R123) has been selected as a fluorescent model template to prove the recognition capability of the MIP nanostructures, which has been evaluated by fluorescence lifetime imaging microscopy (FLIM) with single photon timing measurements. The binding selectivity provided by the imprinting effect has been confirmed in the presence of compounds structurally related to R123. These results pave the way to the development of nanomaterial architectures with biomimetic artificial recognition properties for environmental, clinical and food testing.

Validation of a confirmatory method for lipophilic marine toxins in shellfish using UHPLC-HR-Orbitrap MS

Lipophilic marine toxins are produced by harmful microalgae and can accumulate in edible filter feeders such as shellfish, leading to an introduction of toxins into the human food chain, causing different poisoning effects. During the last years, analytical methods, based on liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), have been consolidated by interlaboratory validations. However, the main drawback of LC-MS/MS methods remains the limited number of compounds that can be analyzed in a single run. Due to the targeted nature of these methods, only known toxins, previously considered during method optimization, will be detected. Therefore in this study, a method based on ultra-high-performance liquid chromatography coupled to high-resolution Orbitrap mass spectrometry (UHPLC-HR-Orbitrap MS) was developed. Its quantitative performance was evaluated for confirmatory analysis of regulated lipophilic marine toxins in shellfish flesh according to Commission Decision 2002/657/EC. Okadaic acid (OA), dinophysistoxin-1 (DTX-1), pectenotoxin-2 (PTX-2), azaspiracid-1 (AZA-1), yessotoxin (YTX), and 13-desmethyl spirolide C (SPX-1) were quantified using matrix-matched calibration curves (MMS). For all compounds, the reproducibility ranged from 2.9 to 4.9 %, repeatability from 2.9 to 4.9 %, and recoveries from 82.9 to 113 % at the three different spiked levels. In addition, confirmatory identification of the compounds was effectively performed by the presence of a second diagnostic ion ((13)C). In conclusion, UHPLC-HR-Orbitrap MS permitted more accurate and faster detection of the target toxins than previously described LC-MS/MS methods. Furthermore, HRMS allows to retrospectively screen for many analogues and metabolites using its full-scan capabilities but also untargeted screening through the use of metabolomics software.

DNA barcoding and microsatellites help species delimitation and hybrid identification in endangered galaxiid fishes

The conservation of data deficient species is often hampered by inaccurate species delimitation. The galaxiid fishes Aplochiton zebra and Aplochiton taeniatus are endemic to Patagonia (and for A. zebra the Falkland Islands), where they are threatened by invasive salmonids. Conservation of Aplochiton is complicated because species identification is hampered by the presence of resident as well as migratory ecotypes that may confound morphological discrimination. We used DNA barcoding (COI, cytochrome b) and a new developed set of microsatellite markers to investigate the relationships between A. zebra and A. taeniatus and to assess their distributions and relative abundances in Chilean Patagonia and the Falkland Islands. Results from both DNA markers were 100% congruent and revealed that phenotypic misidentification was widespread, size-dependent, and highly asymmetric. While all the genetically classified A. zebra were correctly identified as such, 74% of A. taeniatus were incorrectly identified as A. zebra, the former species being more widespread than previously thought. Our results reveal, for the first time, the presence in sympatry of both species, not only in Chilean Patagonia, but also in the Falkland Islands, where A. taeniatus had not been previously described. We also found evidence of asymmetric hybridisation between female A. taeniatus and male A. zebra in areas where invasive salmonids have become widespread. Given the potential consequences that species misidentification and hybridisation can have for the conservation of these endangered species, we advocate the use of molecular markers in order to reduce epistemic uncertainty.

Immuno-like assays and biomimetic microchips

Biomimetic assays with molecularly imprinted polymers (MIPs) are bound to be an alternative to the traditional immuno-analytical methods based on antibodies. This is due to the unique combination of advantages displayed by the artificial materials including the absence of animal inoculation and sacrifice, unnecessary hapten conjugation to a carrier protein for stimulated production, the possibility of manufacturing MIPs against toxic substances, excellent physicochemical stability, reusability, ease of storage, and recognition in organic media. If the selectivity and affinity of MIPs are increased, many more immuno-like assays will be developed using radioactive, enzymatic, colorimetric, fluorescent, chemiluminescent, or electrochemical interrogation methods. This chapter provides a comprehensive comparison between the bio- and biomimetic entities and their usage.

[Long term consequences among children exposed to lead poisoning]

BACKGROUND

In 1996 there was a massive lead poisoning in a southern rural community in Chile. The contamination source was a mill whose grinding stone was repaired with lead and contaminated the flour.

AIM

To assess the presence of sequelae ten years later, among subjects that were exposed to lead on that occasion.

MATERIAL AND METHODS

Cross sectional study of 77 individuals (47 males), aged 10 to 25 years, that were exposed to lead in 1996 and were treated with EDTA.

RESULTS

Twenty one percent of subjects had a subnormal intelligence quotient (IQ). The risk of having a low IQ was significantly higher among those exposed before the age of six years. IQ was significantly lower among subjects that, immediately after the exposure, had a lead level over 48 microg/dl, compared with those that had a lead level below 43 microg/dl (86.7+/-7.3 and 93+/-11.6 respectively). No subjects with high blood pressure or evidences of nephrotoxicity were detected.

CONCLUSIONS

Subjects aged less than six years at the moment of lead exposure had a lower IQ when assessed ten years later.

Influence of surface hydroxylation on 3-aminopropyltriethoxysilane growth mode during chemical functionalization of GaN Surfaces: an angle-resolved X-ray photoelectron spectroscopy Study

A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown on sapphire substrates by metal-organic chemical vapor deposition was carried out. Both types of samples were chemically functionalized with 3-aminopropyltriethoxysilane (APTES) using a well-established silane-based approach for functionalizing hydroxylated surfaces. The untreated surfaces as well as those modified by hydroxylation and APTES deposition were analyzed using angle-resolved X-ray photoelectron spectroscopy. Strong differences were found between the APTES growth modes on n- and p-GaN surfaces that can be associated with the number of available hydroxyl groups on the GaN surface of each sample. Depending on the density of surface hydroxyl groups, different mechanisms of APTES attachment to the GaN surface take place in such a way that the APTES growth mode changes from a monolayer to a multilayer growth mode when the number of surface hydroxyl groups is decreased. Specifically, a monolayer growth mode with a surface coverage of approximately 78% was found on p-GaN, whereas the formation of a dense film, approximately 3 monolayers thick, was observed on n-GaN.

Molecularly imprinted polymers with a streamlined mimic for zearalenone analysis

Molecularly imprinted polymers (MIPs) with selective recognition properties for zearalenone (ZON), an estrogenic mycotoxin, and structurally related compounds have been prepared using the non-covalent imprinting approach. A rationally designed ZON analogue, cyclododecyl 2,4-dihydroxybenzoate (CDHB), that exhibits resemblance to ZON in terms of size, shape and functionality has been synthesized and used as template for MIP preparation instead of the natural toxin. Several functional monomers have been evaluated to maximize the interactions with the template molecule during the polymerization process. The polymer material prepared with 1-allylpiperazine (1-ALPP) as functional monomer, trimethyl trimethacrylate (TRIM) as cross-linker and acetonitrile as porogen (in a 1:4:20 molar ratio) displayed superior binding capacities than any other of the MIPs tested. Selectivity of this material for ZON and structurally related and non-related compounds has been evaluated using it as stationary phase in liquid chromatography. Our results demonstrate that the imprinted polymer shows significant affinity in the porogenic solvent for the template mimic (CDHB) as well as for the ZON and other related target metabolites in food samples, dramatically improving the performance of previously reported MIPs for ZON recognition. Therefore, MIPs can be an excellent alternative for clean-up and preconcentration of the mycotoxin in contaminated food samples.

[Prevalence of psychiatric disorders in men and women hospitalized in a internal medicine service of a hospital of Santiago, Chile]

BACKGROUND

Mental disorders may interfere, aggravate or mimic medical conditions.

AIM

To study the prevalence of psychiatric disorders among patients hospitalized in a medical ward of a general hospital.

PATIENTS AND METHODS

A structured interview for DSM-III, devised for "non patients", was applied to 203 men and 203 women, aged 11 to 90 years old, hospitalized in an internal medicine service of a public hospital. Thirty four psychiatric conditions that can be discriminated with the instrument and others that complied with DSM-III criteria, were investigated.

RESULTS

There was a 60% prevalence of mental disorders among men (alcohol dependency in 26%, delirium or dementia in 10.8%, anxiety disorders in 10.4%, major depression in 7.8% and adaptation disorders in 3%). Among women, the prevalence of mental disorders was 65% (major depression in 23.2%, anxiety disorders in 14.3%, adaptation disorders in 8.4%, dementia in 5.6%, delirium in 3% and alcohol dependency in 2.5%). Most conditions were of moderate or mild intensity. Two or more conditions coexisted in 40% of cases. Only in 8% of these subjects, a psychiatric consultation was requested.

CONCLUSIONS

There is a high frequency of psychiatric disorders among medical patients. These must be adequately diagnosed and treated.

Fiber-optic luminescent sensors with composite oxygen-sensitive layers and anti-biofouling coatings

Anti-biofouling polymers containing phosphorylcholine (PC)-substituted methacrylate units have been prepared by copolymerization with dodecyl methacrylate and used to coat luminescent oxygen sensors. Nanometer-sized coatings of such materials are shown to reduce significantly the adhesion of marine bacteria (more than 70%) and thrombocytes (more than 90%) to the surface of tris-(4,7-diphenyl-1,10-phenanthroline)ruthenium(II)-doped silicone layers. A thorough analytical characterization of both the PC-coated and the uncoated dyed films has demonstrated that the anti-biofouling layers do not alter dramatically the performance of the fiber-optic oxygen sensors in aqueous media and are mechanically stable for more than one year of continuous immersion. The slope of the linear calibration plots in the 0-8 mg L(-1) oxygen concentration range (ca. 1.0 L mg(-1)) decreases 8-11% after applying the 50-nm protective layer with no change in the sensor precision (1.1-1.9% RSD, n = 6). The response time of the 200-microm O2-sensitive layers (1.5-6 min) increases up to 2-fold, depending on the nature of the PC polymer used, but the temperature effect on the sensor response (0.020 L mg(-1) degrees C(-1)) remains essentially unchanged. Oxygen detection limits as low as 0.04 mg L(-1) have been measured with the coated optodes. The novel biofouling-resistant optosensors have been successfully validated against a commercial oxygen electrode and are shown to respond faster than the electrochemical device for large oxygen concentration changes. The biomimetic coatings will be particularly useful for drift-free long-term operation of environmental optosensors and in vivo fiber-optic oxygen analyzers.

Luminescence quenching by DNA-bound viologens: effect of reactant identity on efficiency and dynamics of electron transfer in DNA

Photoinduced electron transfer from two intercalating photoactive donors, Ru(phen)2dppz2+ and ethidium, to intercalating viologen acceptors of the N,N'-dialkyl-6-(2'-pyridiniumyl)phenanthridinium family has been investigated through steady-state and time-resolved luminescence quenching measurements. Efficient quenching of the emission from these donors bound to DNA is observed at low concentrations of acceptor (1-10 eq.), and in time-resolved emission experiments it is determined that electron transfer occurs on the nanosecond time scale. Furthermore, transient absorption measurements confirm that the quenching is the result of a charge-transfer process; upon photoreaction of intercalated Ru(phen)2dppz2+ with a viologen acceptor, an intermediate with spectral properties resembling the expected charge-separated pair is observed. The quenching yields and kinetics obtained with this quencher are in marked contrast to those observed with these same donors paired with Rh(phi)2bpy3+ as an acceptor. The differing efficiencies of electron transfer for these donor/acceptor pairs bound to DNA as compared to others previously described are discussed qualitatively in terms of the structural and electronic properties of the different reactants.

A ruthenium probe for cell viability measurement using flow cytometry, confocal microscopy and time-resolved luminescence

The capability of the new luminescent probe (dibenzo[h,j] dipyrido[3,2-a:2',3'-c]phenazine)bis(2,2'-bipyridine)ruthenium(II) dication, (RB2Z), to discriminate live and dead cells has been tested on rat hepatocytes and mouse lymphocytes. RB2Z-stained cells were analyzed using flow cytometry, fluorescence (confocal) microscopy and time-resolved luminescence measurements. The established viability probes propidium iodide (PI) and SYTOX green (SG) were used as controls. The intense luminescence of RB2Z at 606 nm is localized in the nucleus of nonviable cells. Viability measurements by flow cytometry and fluorescence microscopy using RB2Z as dead-cell marker yield the same results as PI and SG. The luminescence lifetime of RB2Z also displays sensitivity to cell viability (0.45 and 0.82 microsecond in presence of fully viable and dead cells, respectively). This ruthenium complex is photostable under laser sources and its 200 nm Stokes shift facilitates multicolor labeling experiments in flow cytometry and fluorescence microscopy. Unlike the currently available probes, the long-lived excited state of RB2Z also allows assays based on luminescence decay measurements.

[Attempted suicide in females: a prospective study]

BACKGROUND

A previous suicide attempt is one of the strongest predictors of future suicidal behavior.

AIM

To explore the evolution of suicidal tendencies in women who attempted suicide 5 to 7 years earlier.

PATIENTS AND METHODS

Ninety two women aged 37 +/- 9 years old, that attempted suicide between 1989 and 1991 were followed and reassessed in 1997.

RESULTS

In the study period two women committed suicide and 30 attempted suicide. Forty three percent of new self harm behaviors occurred during the first year after the first suicide attempt and the harming method was similar.

CONCLUSIONS

In this study, 34% of women with previous suicide attempts, repeated this behavior, using similar methods.

The interaction of DNA with intercalating agents probed by sodium-23 NMR relaxation rates

We have investigated the changes of Na-23 NMR spin-lattice and spin-spin relaxation rates of Na-DNA in dilute aqueous solutions, induced by the intercalating drugs ethidium, propidium, 6,7-dihydro-pyrido[2',1':3,4]pyrazino[1,2-f]-phenanthridinediium dihydrate (dq2pyp) and by the electrostatic binder Mg2+. It has been found that the Na-23 spin-lattice relaxation is monoexponential, while the spin-spin relaxation follows a biexponential law. From the linear trends of the relaxation rates observed in the titration experiments of Na-DNA with the drugs we inferred the validity of a two-site model in the fast exchange limit. The relaxation rates of sodium in the bound state have been estimated by using the fraction of bound sodium ions per phosphate charge, predicted by the counterion condensation theory, and the number of sodium ions released per bound drug, calculated from salt dependent equilibrium binding studies. The results show that the addition of the competitors slow down the broad component of the spin-spin relaxation rate of bound sodium in the order dq2pyp approximately propidium < ethidium < Mg2+. This reduction is shown to be due mainly to the decrease of the quadrupolar coupling constant for the slow motions, thus indicating a decrease of the average electric field gradient at the sodium ions close to the DNA surface. We also show that the broad component of the spin-spin relaxation rate linearly correlates with the relative non-polyelectrolyte free energy. This result is discussed in terms of the non-polyelectrolyte interactions affecting R2bB, which can be partitioned into stacking interaction and interactions involving the molecular moieties of the intercalators exposed to the solvent in the minor groove.

In vitro evaluation of antifungal properties of 8.O.4'-neolignans

Eighteen racemic 8.O.4'-neolignans with six different substitution patterns in rings A and B, in their ketone and in their erythro and threo alcoholic forms, were evaluated for antifungal activity by the agar dilution method. Only the alcohols exhibited a broad spectrum of activities against Microsporum canis, Microsporum gypseum, Tricophyton mentagrophytes, Tricophyton rubrum, and Epidermophyton floccosum. (+/-)-erythro-3,4-(methylenedioxy) -7-hydroxy-1'-allyl-3',5'-dimethoxy-8.O.4'-neolignan (11) was the most active compound in the series, and E. floccosum was the most susceptible species.

Sequence specificity, enantiospecificity and polyelectrolyte effect in the binding to DNA of a 6-(2-pyridyl)phenanthridine chiral photonuclease

In order to establish the basis for the rational design of a novel family of intercalating chiral photonuclease drugs aimed at photochemotherapy, namely N, N'-dialkylated 6-(2-pyridinium)phenanthridinium (pyp) dications, a detailed investigation of the DNA binding of the dq2pyp member (where dq2 stands for -CH2CH2-), was conducted. The study addresses the sequence- and enantiospecificity, as well as polyelectrolyte effects in the drug-DNA interaction. Binding isotherms with synthetic polynucleotides, forcefield calculations, affinity chromatography in a DNA-cellulose stationary phase and salt-dependent equilibrium and kinetic studies with DNA were used. dq2pyp shows a strong preference for alternating GC over AT base pairs; binding to homopolymeric DNA is weak (< 3 x 10(4) M-1). Affinity chromatography shows enantiospecific binding of dq2pyp to DNA. The polyelectrolyte contribution to the binding free energy are shown to be relatively important (-4.8 kcal/nmol out of an overall value of -7.2 kcal/mmol at 10.2 mM Na+). The slope of the logkd (dissociation rate constant) vs. log[Na+] plot (0.7) agrees with the values predicted from counterion condensation theory for a dicationic intercalator, giving further support to such a DNA binding mode for dq2pyp. The relatively high kinetic dissociation constants (logkd = 0.70log[Na+] + 3.79) in comparison with those of propidium (two orders of magnitude larger at any Na+ concentration) seems to originate from the absence of amino groups in dq2pyp. The kinetic association constants (logka = -1.06log[Na+] + 5.53) are twice these of propidium, probably due to the less restrictive positioning of dq2pyp at the intercalation site. The kinetic studies support a mechanism of intercalation in which the drug forms a pre-equilibrium outside the complex followed by the intercalation of the drug. Molecular modelling is used throughout to rationalize all the experimental data, as well as to propose new candidates with improved DNA affinity and residence time.

Photoinduced electron transfer from nucleotides to DNA intercalating viologens. A study by laser-flash photolysis and spectroelectrochemistry

Fluorescent DNA-binding N,N'-dialkyl 6-(2-pyridinium)phenanthridinium dications (where dialkyl stands for -(CH2)2-or-(CH2)3-, abbreviated dq2pyp and dq3pyp, respectively) associate with GMP (guanosine-5'-monophosphate) in 0.1-mol l-1, pH 3.5-5.5, phosphate buffer solution to yield 1:1 and 1:2 non-emissive complexes, the formation constants of which range from 197-63 and 19-11 l mol-1, respectively. In addition to the strong static quenching, dynamic deactivation of their excited state occurs at diffusion-controlled rate ki = 5.2 x 10(9) l mol-1 s-1). Illumination of the GMP-containing solutions of the dyes with a 355 nm laser pulse produces a transient, with strong absorbance at 510 and 720 nm for dq2pyp, and 420 and 560 nm for dq3pyp. An identical transient is produced in the presence of ascorbic acid instead of the mononucleotide. By comparison to the electrochemically generated absorption spectra of the monoreduced dyes, the photogenerated transients have been assigned unequivocally to their corresponding radical-cations, formed by electron transfer to the anglet excited state. The back redox reaction between the oxidized quencher and dq2pyp+ proceeds at a rate of 1-2 x 10(9) l mol-1 s-1. The same transient has been observed also for the DNA intercalated viologens; this result, together with the little ability of these dyes to sensitize the formation of singlet dioxygen or to produce superoxide anion, demonstrate that their DNA photocleavaging activity is initiated by an efficient light-induced electron transfer from the nucleobases.

DNA photocleavage by novel intercalating 6-(2-pyridinium)phenanthridinium viologens

A new type of DNA-intercalating viologen dications, derived from the N,N'-dialkyl-6-(2-pyridyl)phenanthridine structure (in which dialkyl is -CH2CH2-,-CH2CH2CH2-, or (-CH3)2, abbreviated dq2pyp, dq3pyp, and Me2pyp, respectively), are able to produce frank strand breaks in supercoiled plasmid DNA upon irradiation with visible light. The amount of photocleavage is similar for the three drugs. The observed DNA photosensitization appears to follow a single-strand cleavage model, as shown by a kinetic analysis of the reaction with dq2pyp. The photodynamic action of the drugs seems to be initiated by a light-induced electron transfer reaction from the nucleobases, given the singlet excited-state redox potentials (ca. + 2.1 V vs. SHE) and the low quantum yields of singlet molecular oxygen production of the drugs (0.1-0.2 in aerated D2O).

[Suicidal behavior in Chilean women. The epidemiological web of societal and individual factors]

Presented study concerned epidemiology and psychological factors of suicide behavior aiming at establishing preventive measures and criteria for crisis intervention.

Stereospecific DNA binding of luminescent atropisomeric viologens

Binding to B-DNA of one enantiomer of dq3pyp, --a member of a novel family of intercalating luminescent viologens derived from N,N'-dialkyl-6-(2-pyridyl)phenanthridine, in which dialkyl is -(CH2)2- (dq2pyp), -(CH2)3- (dq3pyp), or (-CH3)2 (Me2pyp)--, is strongly favored compared to its estable atropisomer. Evidence of the stereospecific interaction has been gained by resolution of a rac-dq3pyp mixture upon dialysis in the presence of DNA, monitored by circular dichroism. Molecular modeling suggests that the S enantiomer of both dq3pyp and dq2pyp is the one preferred for the binding. No similar resolution has been achieved with rac-dq2pyp due to the lower barrier to interconversion of its atropisomers, as shown by 1H-NMR. The identical binding energy of the two modeled diastereoisomeric Me2pyp-DNA complexes discard enantiospecific interaction of this drug. Affinity chromatography on DNA-cellulose allows isolation of the pure enantiomers of dq3pyp.

[Anticoagulation in hemodialysis with a single dose of low molecular weight heparin]

The aim of this work was to compare the benefits and problems of low molecular weight heparin use in chronic hemodialysis, compared to conventional heparin. We studied 35 patients that received low molecular weight heparin (Enoxaparine, molecular weight 4000) during 115 consecutive hemodialysis procedures and conventional heparin during the subsequent 35 procedures. We assess the heparin dose, partial thromboplastin time before dialysis and at 3 and 120 min during the procedure, arterio-venous fistula compression time, clot formation in the circuit and residual volume of filters. Median total dose of conventional heparin was 6289 U (range 3000-10000) compared to 5555 U (range 2000-8000) of low molecular weight heparin. When the dose was calculated per kg of body weight, it was lower for low molecular weight heparin than for conventional heparin (87.8 U (range 33-100) vs 100 U (range 50-176)). Partial thromboplastin time achieved was lower with low molecular weight heparin, compared with conventional heparin, at 3 (64.26 vs 125.2 sec) and 120 min (39.1 vs 84.45 sec). Clot formation, arteriovenous fistula compression time and residual volume of filters were similar for both types of heparin. It is concluded that a single dose of low molecular weight heparin simplifies anticoagulation during hemodialysis, modifies less the partial thromboplastin time and does not alter filter re-utilization.

Interaction with DNA of photoactive viologens based on the 6-(2- pyridinium)phenanthridinium structure

A new type of DNA-interacting violgens derived from the N,N'-dialkyl 6-(2-pyridinium)-phenanthridinium structure (in which dialkyl is -CH2CH2-,-CH2CH2CH2-, or (-CH3)2) have been synthesized. Electronic spectroscopy, steady-state and time-resolved fluorescence, cyclic voltammetry, binding isotherms, viscosity titrations, and molecular modeling techniques were employed to characterize the structural, photophysical and redox properties of the novel drugs as well as the corresponding drug-DNA complexes. The viologens display significant visible absorption (up to ca. 490 nm), and a rather intense luminescence (phi cm from 0.06 to 0.20 at 491-565 nm wavelength maxima) which is efficiently quenched by DNA. The calculated redox potentials of these drugs in their singlet excited state (+2.1 V vs. SHE) predict a large driving force for a photoelectron transfer reaction from the nucleobases to the drugs. Photochemical measurements of the viologens in the presence of mononucleotides, nucleosides, and deoxyribose indicate that the observed fluorescence quenching occurs indeed by electron transfer from the DNA bases rather than the sugar phosphate backbone. Large association constants to double helical DNA (in the order of 10(5) M-1) have been evaluated from the absorbance-based binding isotherms. Viscosimetry supports intercalation of the drugs into the DNA helix. Computer simulations (molecular mechanics of d(CGCGCG)2-drug complexes) confirm the intercalative nature of the binding and provide finer details about the geometry of the different viologen-DNA complexes. Molecular modeling has also revealed a stereoselective interaction of the enantiomeric drug conformers with the chiral DNA helix. A DNA-targeted drug design of future generations of these ligands in order to improve and/or modulate their photochemical, redox, and nucleic acid binding properties appears to be possible by a careful selection of the N,N'-dialkylating chain and/or the substituents on the azaheterocyclic moieties.

[A kinetic model for heparin dosing in patients on chronic hemodialysis]

The quality of anticoagulation was evaluated in 5 patients receiving heparin during chronic hemodialysis. 50 kinetic studies were performed using 2 monitoring tests, TTPK and TCK. Basal and intradialysis measurements were used to estimate sensitivity and the elimination constant according to formulae described by Milthorpe. Mean basal TTPK time was 27.3 sec and TCK time was 211 sec. Mean initial intradialysis TTPK time was 107.5 sec and after correction applying the kinetic model it was 62 sec. Intradialysis TCK time varied from 806 to 683 sec after correction. At the end of the study, mean intradialysis TTPK time was 61 sec not significantly different from the target time of 55 sec. TCK time, however, was significantly greater than target (684 vs 434 sec).

Photoinduced electron transfer quenching of excited Ru(II) polypyridyls bound to DNA: the role of the nucleic acid double helix

In the presence of double helical polynucleotides (sodium poly(dA-dT).poly(dA-dT) or calf thymus DNA), the efficiency of oxidative or reductive electron transfer between photoexcited ruthenium(II) chelates Ru(tap)2(hat)2+ or Ru(phen)2+(3) (where tap = 1,4,5,8-tetraazaphenanthrene, hat = 1,4,5,8,9,12-hexaazatriphenylene, and phen = 1,10-phenanthroline) and appropriate cationic quenchers (ethidium, Ru(NH3)3+(6), methyl viologen, or M(phen)3+(3), where M = Co, Rh, Cr) increases 1-2 orders of magnitude compared to the efficiency of the same quenching in microhomogeneous aqueous medium (kq = 0.3-1.8 x 10(9) M-1 s-1). The enhancement is more pronounced when the binding constant of the quencher (10(3) less than Kb less than 10(6) M-1) is large. Similar trends are found when the biopolymers are replaced by sodium poly(styrenesulfonate) (PSS). The accelerated electron transfer process is proposed to be due mainly to the effect of accumulation of the reagents in the electrostatic field of the polymer; if corrections for this effect are introduced (e.g. ratioing [quencher]/[polynucleotide]), the reaction rate becomes essentially independent of the polymer concentration. Based upon a model for electron transfer reaction of the complexes within a small cylindrical interface around the DNA helix, calculations of the bimolecular electron transfer rate constants are computed to be 10(3) times smaller when the reactants are bound to the double-stranded polynucleotides and decreased mobility of the cationic species is apparent. The effect is less pronounced if a simpler polyelectrolyte (PSS) is employed. Emission lifetimes of the Ru(II) polypyridyls bound to the DNA (0.32-2 microseconds, double exponential decays) are discussed as well.

Ligand-dependent interaction of ruthenium(II) polypyridyl complexes with DNA probed by emission spectroscopy

The nature of the interaction in buffered aqueous solution of several homo and heteroleptic ruthenium(II) polypyridyl complexes containing 2,2'-bipyridine (bpy), 2,2'-bipyrazine (bpz), 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (dip), 3,4,7,8-tetramethyl-1,10-phenanthroline (tmp), 1,4,5,8-tetraazaphenanthrene (tap), and 1,4,5,8,9,12-hexaazatriphenylene (hat) with calf thymus DNA and poly(dA-dT).poly(dA-dT) (pdAT) has been investigated by steady-state spectroscopy and emission lifetime measurements. Those complexes containing two or more tap/hat ligands photo-oxidize the guanine base upon binding to DNA with efficiencies that parallel their excited state redox potentials, but display "normal" behavior (increase of both the emission intensity and lifetime) when bound to pdAT. However Ru(tap)(hat)2+2 and Ru(hat)2+3 even photooxidize the adenine base of pdAT, so that their excited states are also quenched in the presence of either polynucleotide. The electron transfer quenching mechanism has been confirmed previously by detection of the monoreduced complex in laser flash photolysis experiments in the presence of mononucleotides. Most of the complexes investigated appear to bind to DNA, at least in part via intercalation, with affinities being dependent on the nature of the largest ligand (hat shows the highest ability in heteroleptic complexes). From lifetime quenching experiments, in the presence of moderate amounts of NaCl, surface binding does not appear to be a general mode for the complexes investigated, and it has been demonstrated unequivocally only for Ru(phen)2+3. In addition, the intercalation of complexes into DNA increases as the ionic strength of the medium decreases, the DNA/Ru ratio increases, or when water is partially replaced by glycerol.