Redox switching of heteropolyanions entrapped in polypyrrole films investigated by ac electrogravimetry.

In this work, the global kinetics and the exchange of protons and free solvent at the film/electrolyte interface were investigated when a PPy film doped with HPA (heteropolyanions) is polarized. The ionic and electronic transfers for the PPy-HPA system are fast because the determined values of the resistances are relatively low (a few ohms). Depending on the applied potential, the global kinetics is controlled by both the ionic and electronic transfers. The transport effects were neglected here because the prepared films were very thin. Protons play an important role in charge compensation whatever the imposed potential on the PPy-HPA film. This phenomenon results from the acidic-basic properties of the SiMo(12)O(40)(4-) reduced species. A small quantity of water was also shown to be involved in the film reaction process.

Improved frequency/voltage converters for fast quartz crystal microbalance applications.

The monitoring of frequency changes in fast quartz crystal microbalance (QCM) applications is a real challenge in today's instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1 kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10 mVHz, for a frequency shift resolution of 0.1 Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5 to 10 MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications.

New frequency/voltage converters for ac-electrogravimetric measurements based on fast quartz crystal microbalance.

A better understanding of the mechanisms located at the solid/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the only difference is the determination of mass changes given by the quartz crystal microbalance rather than current changes following sine wave modulations of the applied potential. This function appears very well adapted to characterize ionic exchanges at the electrochemical interface. Frequency/voltage converters are the key devices in translating the microbalance frequency response in terms of a continuous voltage change. The latter allows the transfer function to be obtained via a frequency response analyzer. Different converters were tested in this work in order to improve the performances of the experimental setup.

Kinetic aspects of ion exchange in KhFek[Fe(CN)6]l*mH2O compounds: a combined electrical and mass transfer functions approach.

The present paper quantifies and develops the kinetic aspects involved in the mechanism of interplay between electron and ions presented elsewhere(1) for K(h)Fe(k)[Fe(CN)(6)](l)*mH(2)O (Prussian Blue) host materials. Accordingly, there are three different electrochemical processes involved in the PB host materials: H(3)O(+), K(+), and H(+) insertion/extraction mechanisms which here were fully kinetically studied by means of the use of combined electronic and mass transfer functions as a tool to separate all the processes. The use of combined electronic and mass transfer functions was very important to validate and confirm the proposed mechanism. This mechanism allows the electrochemical and chemical processes involved in the K(h)Fe(k)[Fe(CN)(6)](l)*mH(2)O host and Prussian Blue derivatives to be understood. In addition, a formalism was also developed to consider superficial oxygen reduction. From the analysis of the kinetic processes involved in the model, it was possible to demonstrate that the processes associated with K(+) and H(+) exchanges are reversible whereas the H(3)O(+) insertion process was shown not to present a reversible pattern. This irreversible pattern is very peculiar and was shown to be related to the catalytic proton reduction reaction. Furthermore, from the model, it was possible to calculate the number density of available sites for each intercalation/deintercalation processes and infer that they are very similar for K(+) and H(+). Hence, the high prominence of the K(+) exchange observed in the voltammetric responses has a kinetic origin and is not related to the amount of sites available for intercalation/deintercalation of the ions.

Thermodynamic aspects of ion intercalation in KhFek[Fe(CN)6]l*mH2O compounds: application to the Everit's Salt/Prussian blue transition.

The K(+) reversible processes for ion exchange in K(h)Fe(k)[Fe(CN)(6)](l)*mH(2)O host compounds (Prussian Blue) were thermodynamically analyzed. A thermodynamic approach was established and developed based on the consideration of a lattice-gas model where the electronic contribution to the chemical potential is neglected and the ion-host interaction is not considered. The occupation fraction of the intercalation process was calculated from the kinetic parameters obtained through ac-electrogravimetry in a previous paper. In this way, the mass potential transfer function introduces a new way to evaluate the thermodynamic aspect of intercalation. Finally, based on the thermodynamic approach, the energy used to put each K(+) ion into the host material was calculated. The values were shown to be in good agreement with the values obtained through transient techniques, for example, cyclic voltammetry. As a result, this agreement between theory and experimental data validates the thermodynamic approach considered here, and for the first time, the thermodynamic aspects of insertion were considered for mixed valence materials.

Mechanism for interplay between electron and ionic fluxes in KhFek[Fe(CN)6]l.mH2O compounds.

This paper develops a framework for the interpretation of ionic insertion/deinsertion reactions in an aqueous environment taking place in transition-metal hexacyanoferrates of the general formula K(h)[Fe(2+) (CN)(6)](l).mH(2)O, also called Prussian Blue. Three different processes were fully separated in the electrochemistry of these films. It was clearly identified that one of these electrochemical processes involves the insertion/deinsertion of H(3)O(+) (hydrated protons) through the channels of the K(h)[Fe(2+) (CN)(6)](l).mH(2)O structure to reach the film electroneutrality during the electron transfer between Everitt's Salt and Prussian Blue. The other electrochemical processes involve K(+) or H(+) (proton) exchange through the water crystalline structure existing in the channels of the K(h)[Fe(2+)(CN)(6)](l).mH(2)O structure.

Oligonucleotide quartz crystal microbalance sensor for the microalgae Alexandrium minutum (Dinophyceae).

We report the immobilization on a gold surface of a 20-base DNA probe labeled with disulfide group and on the selective hybridization with the complementary 20-base DNA strand. The oligonucleotide probe is the complementary strand of a partial sequence of the gene encoding for a large ribosomal RNA sub-unit which is a coding sequence of Alexandrium minutum DNA, a microalgae that produces neurotoxins responsible for paralytic shellfish poisoning on European and Asian coasts. The kinetics of DNA probe immobilization and hybridization were monitored in situ by using a 27 MHz quartz crystal microbalance under controlled hydrodynamic conditions. The frequency of the setup is stable to within a few hertz, corresponding to the nanogram scale, for 3h and makes it possible to follow frequency change from immobilization of the probe to hybridization of the complementary DNA target. This setup constitutes a biosensor, which is sensitive and selective, and the hybridization ratio between hybridized complementary DNA and immobilized DNA probes is 47%.

Mass and charge balance in self-assembled multilayer films on gold. Measurements with optical reflectometry and quartz crystal microbalance.

This work aimed to the determination of weight uptakes and charge balance in the course of successive deposition of polyelectrolytes, using the so-called self-assembled multilayer technique. Polyelectrolytes were the quaternized polydimethylaminoethyl methacrylate chloride, (MADQUAT) and poly(acrylic acid) (PAA). Experiments were made at pH 5.5 in NaCl solutions between 10(-3) and 10(-1) M. Deposits (5 bilayers) on a gold substrate were monitored using a quartz crystal microbalance (QCM) and optical fixed-angle reflectometry. Analysis of data lead to the determination of the sensitivity factor of the reflectometric output. QCM allowed the direct measurement of weight uptakes in 10(-3) and 10(-2) M solutions, while the viscoelastic properties of the film did not look appropriate for the measurement in 10(-1) M solutions. The layer-by-layer uptakes and charge balances in 10(-3) and 10(-2) M solutions revealed a large contribution of the counterions in the neutralization of the electrical charge in the film, more so for the highly charged MADQUAT polymer. The difference between two successive polymer charge densities increased significantly with the layer number and the electrolyte concentration. The increase of NaCl concentration induced an increase of MADQUAT but reversely a decrease of PAA deposits. The results were consistent with the determining influence of the salt in polyelectrolyte adsorption, both with regards to the concentration and the type of ions that has been well demonstrated in the literature. This work also draws attention to the role of small ions in the structural and application properties of self-assembled multilayer films.

Hereditary 'white nails': a genetic and structural study.

BACKGROUND: Hereditary subtotal leuconychia is a rare nail disease. The gene(s) underlying this phenotype is (are) not known. Immunohistochemical and ultrastructural studies of nails are performed infrequently. OBJECTIVES: To perform genetic linkage analysis and to assess ultrastructure and soft/hard keratin expression in hereditary white nails. METHODS: We have analysed microscopically and ultrastructurally the white nails of a patient from a family in which the trait is inherited in an autosomal dominant manner as an isolated symptom. No skin lesions or hair abnormalities could be detected. Genetic linkage studies were performed on DNA samples obtained from several members of the affected family. A longitudinal surgical biopsy of the nail from a great toe was split in two parts. One part was fixed in formalin and processed for histopathology. Another part was further subdivided and embedded either in Epon, following fixation in 2% glutaraldehyde, or in Lowicryl K4M, after fixation in 3% paraformaldehyde. Dewaxed nail sections and Lowicryl ultrathin sections were also stained with various antikeratin antibodies. RESULTS: Genetic linkage studies of the family pointed to the disease gene mapping to the chromosomal 12q13 region. Genes mapping within this chromosomal region include the genes coding for type II (basic) cytokeratins and hard keratins. The nail matrix presented an abnormal hypergranulosis. The upper part of the nail plate, originating from the proximal nail matrix, had a nonhomogeneous lamellar appearance, with numerous intracellular 'lipidic' vacuoles and 'empty' spaces separating keratin filament bundles. These cells were progressively shed at the nail surface. The cell loss was compensated by hyperproliferation of the distal matrix and of the nail bed keratinocytes, with persistent marked parakeratosis and loose arrangement of keratin bundles. The distal matrix and the nail bed contributed equally to formation of the lower plate. This presented the characteristics of a tissue composed of soft keratins. Accordingly, there was virtually no labelling with the Hb1 antibody to a basic hard keratin in the white nail, whereas the labelling with AE3 antibody to all type II keratins and with KL1 recognizing suprabasal soft keratins was normal or even enhanced. CONCLUSIONS: Genetic linkage indicates that the gene defect underlying the leuconychia in the family studied resides on chromosome 12q13. As the type II keratins map within this chromosomal interval, it is possible that a mutation in one of these keratin genes may be a cause of the hereditary leuconychia. The white appearance of nails in this disease seems to be due to an abnormal keratinization of cells originating from the proximal nail matrix, leading to the presence of abundant intracellular vacuoles and to a lesser compactness of keratins.

[Pachydermatodactyly associated with plantar pachydermy]. / Pachydermodactylie associée à une pachydermie plantaire.

INTRODUCTION: Pachydermodactyly is a superficial fibromatosis located on the proximal portion of fingers'phalanges and interphalangeal joints. Several types of this disease have been described depending on topography, etiology and pathological associations. We report a typical observation of pachydermodactyly associated with a plantar pachydermy. CASE-REPORT: A 19 year-old man was followed for a psychotic disease, associated with mental retardation. On clinical examination, he showed a typical pachydermodactyly, predominantly located on the second, third and fourth fingers of both hands, associated with recent acrocyanosis. A pachydermic aspect was also observed on the external part of the feet sole. Histopathological analysis was identical on digital and plantar lesions with collagen swelling. These lesions extended into the subcutaneous fat only in the feet. DISCUSSION: This observation is compatible with the most classical form of pachydermodactyly which involves several fingers of both hands, usually in men. Furthermore, the association with a psychiatric disorder and the notion of repeated traumatisms have been frequently reported in the literature. However, acrocyanosis and the important disability observed in our case are unusual. Association with plantar pachydermy has never been reported. The identical histological aspect on finger and feet sole suggests that pachydermatodactyly should be integrated in framework of acral pachydermy.

[Systemic lupus erythematosus with disease onset after age 65]. / Lupus érythémateux disséminé survenant après 65 ans.

OBJECTIVES: Systemic lupus erythematosus with disease-onset in the elderly has rarely been studied (only one report about 21 patients with disease onset at 65 and older). Is the management of this pathology modified in this population? METHODS: Seventeen hospitalised cases of lupus patients with disease onset at 65 or older are retrospectively reported between 1988 and 2000. The results are compared with those of younger subjects. RESULTS: The female to male ratio is 1.83. Mean age at disease onset is 71.9 +/- 3.5 years. Mean duration of follow-up is 3.5 +/- 2.4 years. Main initial symptoms are: deterioration of general status (41%), arthritis (35%), cutaneous manifestations (35%), thrombo-embolism (24%) and pleuritis (18%). Malar rash is uncommon (12%). Nephropathy is never a revealing symptom and is rarely serious during the disease's evolution. Like in neurologic manifestations, the etiology has to be discussed in relation to associated co-morbidities. Concerning haematologic features, lymphopenia is found in 82% of the cases with a questionable specificity. Antinuclear antibodies are constant, anti-dsDNA antibodies are found in 82% of the cases, antibodies to extractable nuclear antigens in 50%, and anticoagulant circulating activity in 59%. Prognosis is difficult to assess in such a limited series but 5-years survival probability is 83%. Glucocorticoid lead to 50% of major complications. CONCLUSIONS: This study focuses on the particular initial manifestations of systemic lupus erythematosus in the elderly (deterioration of general status, thrombosis, unusual cutaneous symptoms), and on the specificity of differential diagnosis and treatment.

[Photo-induced sarcoidosis]. / Sarcoïdose photodéclenchée.

INTRODUCTION: Among the multiple forms of clinically atypical cutaneous sarcoidosis, lesions limited to light-exposed areas are rare. We describe a fourth observation. CASE REPORT: A phototype V 51-year-old woman, born in Tunisia presented with papular erythema on the face. Treatment with topical steroids did not result in any improvement. Biopsy specimen revealed a non caseating granuloma according with sarcoidosis. Assessment for systemic sarcoidosis was negative. Phototesting showed no abnormalities. The patient was successfully treated with chloroquine. DISCUSSION: Only three similar observations are reported in the literature. The role of light exposure despite the negative phototesting seems to be real. The tallying of these four observations permits one to isolate photo-induced sarcoidosis as a single entity.

[Sub-total hereditary leukonychia, histopathological and electron microscopy study of "milky" nails]. / Leuconychie héréditaire subtotale. Etude histopathologique et ultrastructure des ongles "laiteux".

INTRODUCTION: Leuconychia is the most common of ungueal discoloration or dyschromia. The hereditary form, sub-total or total, is very rare. We report the observation of a family in which thirteen members, distributed over four generations, presented a partial or subtotal leukonychia of all nails. On the basis of this observation and histopathological analysis of the propositus nail, we discuss the different hypotheses proposed to account for white nails. OBSERVATION: A 45 year-old man without previous medical history, showed partial or sub-total leukonychia of his twenty nails. Clinical examination revealed soft nails with slow growth. Discoloration or dyschromia was associated with koilonychia on the fingers without other cutaneous or visceral abnormalities. A longitudinal biopsy of the whole ungueal apparatus of the large toe was performed. Histopathological analysis showed parakeratosis and an abnormal granular layer thickened on the proximal and ventral womb. These abnormalities were responsible for heterogeneous HES coloration, lamellar and dissociated aspect of the nail plates. Electron microscopy revealed dissociated keratin bundles and the existence of intracytoplasmic clear vacuoles probably of lipid origin. This aspect was observed on the proximal part of the dorsal tablet and disappeared in the distal portion of the nail. DISCUSSION: According to Newton's theorem, a surface appears white when it reflects all the radiation of visible light. This mechanism can be proposed to explain leukonychia. On histological level, parakeratosis and dissociation of the keratin bundles may play a role in the modification of the solar light reflection by ungueal plates. In our case, parakeratosis and disorganization of keratin bundles were present in the white part of the nail, but also in the distal, pinkish crescent (distal dorsal plate). Electron microscopy analysis showed clear vacuoles located in the white part of the nail, whereas they were not seen in the distal part. These observations confirm the probable participation of parakeratosis and keratin abnormalities in this pathology but also suggest an important role of lipid vacuoles. Therefore, some white nails may in fact be "milky" nails. Finally, disorganization of the keratin bundles observed, was also reported in other genodermatosis e.g.: epidermolysis bullosa simplex. In this latter pathology, some hard keratin genes mutations (K5 and K14) have been demonstrated. According to these results, a genetic study is on going in this family in order to search for a mutation in one of the hard keratin genes.

Lymphomatoid papulosis: a localized form with acral pustular involvement.

We report a localized form of lymphomatoid papulosis (LyP) presenting as pustular papules of the hands. The histopathology revealed a moderate inflammatory infiltrate composed of atypical pleomorphic large lymphocytes with atypical mitosis and large nuclei. Epidermotropism could be observed. These atypical cells expressed CD4 and CD30. Laboratory examinations and bone marrow explorations remained negative. The clinical presentation of this case of LyP is unusual. Only histopathological features allowed to diagnose LyP. The knowledge that LyP may be associated with neoplasia or lymphoma underlines the need for a long-term follow-up of these patients.

[Acquired dermal melanocytosis: clinical, pathological and ultrastructural study]. / Mélanocytose dermique acquise: étude anatomo-clinique et ultrastructurale.

INTRODUCTION: Dermal melanocytosis is characterized by the presence of ectopic melanocytes in the dermis. There are several clinical forms. This report describes an unusual case of acquired dermal melanocytosis probably associated with leptomeningeal melanosis. An ultrastructural study was performed. CASE REPORT: A 52-year-old Caucasian woman presented with a fifteen-year history of slowly spreading gray-blue macular pigmentation, associated with multiple blue nevi. Histologic examination revealed dermal melanocytosis. An extracellular sheath surrounded the melanocyte and their cytoplasmic processes. Medullar magnetic resonance findings were compatible with leptomeningeal melanosis. DISCUSSION: Dermal melanocytosis is thought to represent a disorder of neural crest migration. Melanocytes are thought to be aberrant and become arrested during migration, remaining in the dermis. Reactivation of latent dermal melanocytes should explain the pathogenesis of acquired forms. Ultrastructural examinations show an extracellular sheath enclosing dermal melanocytes in all types of dermal melanocytosis.

Multiple idiopathic mucocutaneous neuromas: a new entity?

We report a 53-year-old woman who presented with multiple painful red cutaneous papules that had been growing slowly for 13 years. Histopathology showed typical features of neuroma. Biological, morphological and genetic investigations were negative and excluded the diagnosis of multiple endocrine neoplasia type 2b. After reviewing the literature, we concluded that our patient has an extremely unusual acquired disease, which must be considered as a distinct entity in the spectrum of cutaneous neurological disorders.

Elaboration and characterization of spatially controlled assemblies of complementary polyphenol oxidase-alkaline phosphatase activities on electrodes.

The electrooxidation of a biotin pyrrole has allowed the formation of biotinylated polypyrrole films. Gravimetric measurements based on a quartz crystal microbalance demonstrate the efficient coupling of avidin, biotinylated polyphenol oxidase (PPO-B) and avidin-labeled alkaline phosphatase (AP-A) with the underlying biotinylated polymer film. The estimated mass increase corresponds to the anchoring of 1.6-1.8 equivalent layer of proteins. A step-by-step construction of bienzyme multilayers composed of PPO-B and AP-A was carried out on the electrode surface modified by the biotinylated polypyrrole film through avidin-biotin bridges. A spatially controlled distribution of the two enzymes was performed by the formation of one AP-A layer on 1, 5, and 10 PPO-B layers. The resulting bienzyme electrodes were applied to the determination of phenyl phosphate on the basis of amperometric detection of enzymically generated o-quinone at -0.2 V. Their analytical performances were analyzed in relation to the design of the enzyme architectures and in comparison with the amperometric behavior of the monoenzymatic electrodes (PPO-B electrode and AP-A electrode). It appears that at the 10-layer-PPO-B polypyrrole electrode only 4% of phenol is transformed, whereas 42-69% of phenyl phosphate is enzymatically consumed and detected at the AP-A polypyrrole electrode, depending on the enzyme activity. For the bienzymatic AP-A/PPO-B polypyrrole electrodes, the activity of each immobilized enzyme clearly affects the biosensor performance, the main limiting factor being the very low efficiency of PPO-B at pH 8.8.

[Role of the hemochromatosis gene in prophyria cutanea tarda. Prospective study of 56 cases]. / Rôle du gène de l'hémochromatose (HFE) dans la porphyrie cutanée tardive. Etude prospective de 56 cas.

BACKGROUND: The cause of iron overload in prophyria cutanea tada is unknown. The aim of this work was to determine the frequency of the hemochromatosis gene (HFE) in 56 patients with porphyria cutanea tarda. We analyzed the relationship between HFE mutations and biochemical abnormalities in porphyria cutanea tarda and the interaction with other triggering factors of porphyria cutanea tarda (alcohol abuse, hepatitis C, drugs). PATIENTS AND METHODS: Hepatitis C, alcohol abuse, drug intake and HFE mutations were determined in 56 patients with porphyria cutanea tarda (44 men and 12 women). Iron status was determined from transferrin saturation, serum iron, and serum ferritin. Liver metabolism was determined from liver chemistries: alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transpeptidase. RESULTS: Thirty-nine patients (69.4 p. 100) carried HFE mutations, 18 (32.1 p. 100) were H63D heterozygous, 4 (7.1 p. 100) were H63D homozygous, 9 (16 p. 100) C282Y heterozygous, 8 (14.2 p. 100) compound C282Y/H63D heterozygous and none were C282Y homozygous. Comparison between porphyria cutanea tarda with and without mutations showed that compound C282Y/H63D heterozygous status was significantly linked to iron overload: transferrin saturation=0.61 vs 0.39 (p=0.0001) and serum iron=32.9 vs 22.4 (p=0.0046). H63D homozygous status was linked to iron overload but non-significantly: transferrin sturatin=0.53 vs 0.39 (p=0.06). The class with high iron overload (transferrin saturation > 0.45) was not linked with triggering factors of porphyria cutanea tarda. Hepatatic cytolysis was linked to alcohol abuse and hepatitis C but not to HFE mutations. DISCUSSION: The frequencies of HFE mutations in Lyons France are halfway between Anglo-Saxon and Italian papers, highlighting the Celtic origin of C282Y mutation. Compound heterozygous and to a lesser degree H63D homozygous status explained the highest iron overload in our patients. This favors clinical expression of porphyria cutanea tarda. This iron overload due to HFE mutations is a new triggering factor of porphyria cutanea tarda independent of classical triggering factors: mutation of the erythrocytic uroporpyrinogen decarbocylase gene, alcohol abuse, hepatitis C, and drugs.