Assessment of the Interelectrode Distance Effect over the Omnipole with High Multielectrode Arrays.

The development of high-density multielectrode catheters has significantly advanced cardiac electrophysiology mapping. High-density grid catheters have enabled the creation of a novel technique for reconstructing electrogram (EGM) signals known as "omnipole," which is believed to be more reliable than other methods, especially in terms of orientation independence. This study aims to evaluate how distance affects the omnipolar reconstruction of EGMs by comparing different configurations. Using an animal set up of perfused isolated rabbit hearts, recordings were taken using an ad hoc high-density epicardial multielectrode catheter. Inter-electrode distances ranging from 1 to 4 mm were analysed for their effect on the quality of resulting EGMs. Two biomarkers were computed to evaluate the robustness of the reconstructions: the areas contained within the bipolar loops and the amplitudes of the omnipoles. We hypothesised that both bipolar and omnipolar electrograms would be more robust at shorter inter-electrode distances. The results showed that an increase in distance triggers an increase in loop areas and amplitudes, which supports the hypothesis. This finding provides a more reliable estimate of wavefront propagation for the cross-omnipolar reconstruction method. These results emphasise the importance of distance in cardiac electrophysiology mapping and provide valuable insights into the use of high-density multielectrode catheters for EGM reconstruction.Clinical Relevance- The results of this study have direct clinical relevance in the application of the described techniques to recording systems in the cardiac electrophysiology laboratory, enabling clinicians to obtain more precise characterisation of signals in the myocardium.

Adaptive step ODE algorithms for the 3D simulation of electric heart activity with graphics processing units.

In this paper we studied the implementation and performance of adaptive step methods for large systems of ordinary differential equations systems in graphics processing units, focusing on the simulation of three-dimensional electric cardiac activity. The Rush-Larsen method was applied in all the implemented solvers to improve efficiency. We compared the adaptive methods with the fixed step methods, and we found that the fixed step methods can be faster while the adaptive step methods are better in terms of accuracy and robustness.

In vitro antimicrobial activity of the leaf extract of Harungana madagascariensis Lam. Ex Poir. (Hypericaceae) against strains causing otitis externa in dogs and cats.

Otitis externa in dogs and cats is always caused by a combination of yeasts and bacteria, among which the most important are Malassezia pachydermatis, Staphylococcus intermedius and Pseudomonas species. These organisms often develop resistance to classical antimicrobial agents. Therefore, the aim of this study was to investigate the antimicrobial activities of an ethyl acetate leaf extract of Harungana madagascariensis against the organisms cited, to carry out the phytochemical investigation of this extract and to determine its bioactive chemical class using dilution techniques, the bioautography method and the standard phytochemical method described by Harborne (1973). Phytochemical analysis revealed the presence of saponins, tannins, flavonoids, alkaloids and anthracenic derivatives. The bioassay showed that the antimicrobial properties may be attributed to astilbin, a flavanone derivative identified on the basis of its spectroscopic data. The results suggest that the extract could be used in an antimicrobial preparation effective against the whole range of organisms incriminated in otitis externa in dogs and cats, with a minimal inhibitory concentration (MIC) of 250 microg/ml.

Isolation and in vitro antibacterial activity of astilbin, the bioactive flavanone from the leaves of Harungana madagascariensis Lam. ex Poir. (Hypericaceae).

Harungana madagascariensis is well known for its topical antibacterial properties used in the elaboration of a lot of skin hygiene products. The aim of this study was, on the one hand, to evaluate the in vitro antibacterial activities of aqueous, ethanolic and ethyl acetate crude extracts of Harungana madagascariensis leaves against bacterial strains representative of skin microflora and, on the other hand, to determine the chemical structure of the active compound. Only the ethyl acetate leaf extract presented important antibacterial activity. Its fractionation was carried out by column chromatography using silica gel 60 and it yielded 11 fractions. A bioautographic method, revealed in these fractions the presence of a flavanone as the active compound astilbin or 3-O-alpha-L-rhamnoside-5,7,3',4'-tetrahydroxydihydroflavonol which was identified on the basis of its spectroscopic data. Concerning the antibacterial activity against the representative skin microflora of the armpit and feet, MIC and MBC ranged from 25 to 250 and 100 to 750 microg ml-1, respectively. The results showed that some bacteria considered to be responsible for bad odours at the armpit and feet levels, were destroyed at 200 microg ml-1 (MBC), a concentration sparing most of the useful saprophytic microflora. The minimal inhibitory quantity (MIQs) of astilbin ranged from 50 to 100 microg.

[Study on the inhibitory activity, in vitro, of baicalein and baicalin against skin fungi and bacteria].

In this paper, we concentrated in examining, in vitro, the antiseptic activity of the baicalein and baicalin upon the seventeen pathogenic skin fungal and sixteen skin bacterial strains, these two flavonic compounds were known principally as the biosubstances of a traditional Chinese medicinal plant: Scutellaria baicalensis. In agar media, the baicalein possessed potent specific activity against the pathogenic yeasts with MICs of 70-100 micrograms/ml; But in the same condition, no inhibitory effect was observed upon dermatophytes and filamentous imperfect fungi for baicalein, and upon all used strains for baicalin. According to the antibacterial test of baicalein, a high efficacy was achieved against certain causative specie of axillary and foot's odour such as Micrococcus sedentarius, Staphylococcus epidermidis, S. hominis and C. xerosis with a MICs inferior to 250 micrograms/ml. The good inhibitory activity of baicalein could be linked to the group hydroxyl (-OH) in position seven of the molecule.

Spectrofluorimetric determination of 5-methoxypsoralen pharmacokinetic in patients' serum.

In medicine, psoriasis and vitiligo are most often treated with PUVA therapy (psoralen plus ultraviolet A). The determination of psoralen in patients' blood is necessary, as it is admitted that the therapeutic efficiency depends on drug concentration in patients' serum. The amount of UVA to administer is inversely proportional to serum peak concentration. High-performance liquid chromatography (HPLC) and gas chromatography are the most employed methods for determining psoralens in patients' serum. The 2 techniques are precise and very sensitive, but time consuming. The aim of this paper is to propose a suitable method which is rapid and simple. It is a spectrofluorimetric technique for 5-methoxypsoralen (5-MOP) determination in the serum of patients treated with PUVA therapy. 5-MOP extraction was carried out with an heptane/dichloromethane mixture (4/1; v/v), according to the Stolk method (1980). A calibration curve (CC) was plotted from 5-MOP concentrations (range 50, 100, 200, 300, 400, 500 ng/ml). The CC was linear with a good coefficient of correlation: r = 0.9971, and a suitable coefficient of variation (CV) of 7.0%. The recovery of the method ranged from 85.3 +/- 4.2 to 108 +/- 4.1%. The assay precision gave a CV ranging from 0.10 to 6.90%, with an error inferior to +/-10%. The method did not reveal any interference from serum components on the 5-MOP emission wavelength. The limit of detection of 5-MOP was 15 ng/ml. The proposed procedure was proved to be appropriate for a rapid determination of 5-MOP in patients' serum. This technique could also be employed for other psoralens used in PUVA therapy (e.g., 8-methoxypsoralen).

Psoralens percutaneous permeation across the human whole skin and the epidermis in respect to their polarity (in vitro study).

8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP) and 4,5',8-trimethylpsoralen (TMP) are commonly used in PUVA therapy [psoralen (P) + ultraviolet light A (UVA) irradiation] to treat skin diseases such as psoriasis and vitiligo. In order to predict the choice of the suitable drug(s) for topical applications, with appropriate dosage, percutaneous permeation of the psoralens, in connection with their solubilities and partition coefficients in an octanol/water system, were investigated. The percutaneous penetration experiments were accomplished by the deposit of ethanolic psoralen solution onto human skin and epidermis fragments mounted on Franz cells. Six cells were employed for each psoralen solution and for the whole skin layer as well as for the epidermis. The diffused psoralens in the receptor solution (1.4%, of human serum albumin) were quantified by using high performance liquid chromatography. The solubilities and the partition coefficients (PC) were carried out in an octanol/water system, in triplicate by using spectrofluorimetry. The results demonstrated that cumulated permeated quantities (ng/cm2) over 24 h, across the whole skin and the epidermis were in the following order for the three psoralens: 8-MOP > 5-MOP > TMP. The lipophilicity, expressed via the log PC, was as follows: 1.93 +/- 0.01 (8-MOP), 2.00 +/- 0.01 (5-MOP) and 3.14 +/- 0.01 (TMP). It was inversely correlated with cumulated penetrated amounts over 24 h in both whole skin and epidermis. From these results, TMP could be predicted as the most convenient psoralen for topical applications, because of its weak penetrability. Considering the relationship between psoralens lipophilicity and permeation, only 5-MOP and 8-MOP could be used, topically or orally, especially in the case of generalised skin disorders.

Electric interactions between dust and hot plasmas in the solar system.

Interaction of the charged particles of a plasma with a solid body is an old problem which has been investigated under various conditions, in particular by the authors in several papers. However, the electric potential of the grains may be more sensitive than expected to the physical state of grain matter and the physical parameters of plasmas in the solar system. Using a new model accounting for porosity, a characteristic feature of grains observed in the solar system, we have investigated the secondary electron emission under electron impact for porous materials. The conclusion is that porosity has a significant influence on the rate of electron ejection. It follows that the floating potential of porous grains can be different from that of grains made of bulk material, with consequences for grain dynamics in the environment of planets or comets.

[Improvement of blood filtrability with a purified extract of black currant anthocyanosides in cynomologus monkeys on a fat diet]. / Amélioration de la filtrabilité sanguine par un extrait purifié d'anthocyanosides de cassis chez le singe cynomologue soumis a un régime gras.

A fat diet has been administered for 3 months to Cynomologus monkeys treated with blackcurrant anthocyanosides as compared with others receiving no treatment. Blood filtrability of animals given a fat diet alone was significantly lowered (20.8%; p less than 0.01) as compared with that of animals receiving a standard diet. Blood filtrability of animals receiving a fat diet plus blackcurrant anthocyanosides was not significantly different from that of animals given a standard diet. Emphasis is laid on a new approach to the action of this type of product on blood vessel contents as compared with the known action on the container.