The effect of skin permeation enhancers on the formation of porphyrins in mouse skin during topical application of the methyl ester of 5-aminolevulinic acid

The influence of skin permeation enhancers, such as dimethyl sulphoxide (DMSO) and 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101), Labrafac CC, Labrafil, Labrasol and Transcutol in a concentration of 10% (wt./wt.) on the formation of porphyrins in normal mouse skin from topical application of creams with methyl 5-aminolevulinate (MAL) was studied. The concentration of porphyrins in the mouse skin was determined by direct fluorescence measurements. The results show that studied permeation enhancers increase the formation of porphyrins, and therefore also the skin penetration 2% MAL whereas for 10% and 20% (wt./wt.) MAL concentrations only DMSO, HPE-101 and Labrafac CC increased the porphyrin formation. At all studied MAL concentrations DMSO gave the largest enhancing effect, similarly to that of HPE-101. This suggests that in 2-20% MAL creams HPE-101 may be substituted by Labrafac CC to reduce skin irritation induced by HPE-101 without impairing the porphyrin formation.     

Determination of rosmarinic acid in sage and borage leaves by high-performance liquid chromatography with different detection methods

Rosmarinic acid is separated and identified on the basis of high-performance liquid chromatography (HPLC)-UV-mass spectrometry data in 80% methanol in water extracts from the leaves of Salvia species (S. officinalis, S. glutinosa, S. aethiopis, S. sclarea, and Borago officinalis) as a dominant radical scavenger towards the 2,2'-diphenyl-1-picrylhydrazyl (DPPH*) stable radical in HPLC-DPPH* system. The content of rosmarinic acid in the plants is calibrated and quantitated from chromatograms obtained by UV detection at 280 nm. The concentration ranges from 13.3 to 47.3 mg of the phenolic acid per gram dried leaves of all plants is tested. S. glutinosa and S. sclarea have the highest concentration of rosmarinic acid. The amount of rosmarinic acid in borage leaves is similar compared with Salvia officinalis (15 mg/g). The HPLC-DPPH* system is calibrated for quantitative DPPH* scavenging assessment of rosmarinic acid. The results reveal excellent correlation (r2 = 0.98) between the rosmarinic acid concentration and antiradical activity.     

The current state of analytical control in Lithuania

In Lithuania research and development in chemical analysis are concentrated in scientific institutes and universities. The main fields of interest focus on biosensors, electrochemical sensors, sampling techniques and methods, study of atomization processes in spectrochemical analysis and noise evaluation in analytical measurements. Some laboratories also take part in international environmental monitoring programmes. There are about 50 researchers at the Ph.D. level engaged in analytical chemistry and several hundred technicians specialized in the field of analytical control. About one hundred chemical laboratories are active in scientific institutes, universities and factories. Specialized laboratories of chemical analysis are at the disposal of Environmental Control and Health Protection Departments and forensic investigation organizations. So far no laboratories are accredited according to the ISO 9000 norms. Special courses on analytical chemistry are offered at a few schools of higher education in the country. Only at the Department of Analytical Chemistry of the University of Vilnius specialized programmes are available to postgraduate students working towards a Ph.D. to improve their skills in current techniques of analytical chemistry. Recently the Technical Committee TC-16 for Chemical Analysis was formed within the standardization system of Lithuania. Its main activities are centered on issues such as national terminology, certified reference materials (CRMs), analytical methods and analytical quality assurance. There are numerous problems related to national terminology, the preparation of special documents in the field of analytical control and the production of regional environmental CRMs. Problems, also arise in obtaining and using CRMs for analytical instrument calibration and validation.     

Spectroscopic evidence of monomeric aluminium phthalocyanine tetrasulphonate in aqueous solutions

Aqueous solutions of aluminium phthalocyanine tetrasulphonate (AlPcS(4)) were investigated by means of absorption and fluorescence spectroscopy. The absorption spectrum of AlPcS(4) is independent of concentration in a wide range (from 10(-8) to 10(-4) M). The fluorescence spectrum measured with a standard setup is strongly dependent on AlPcS(4) concentration, and the fluorescence maximum is gradually red-shifted with increasing concentration. Calculations that take into account reabsorption of fluorescence (inner-filter effect) fit the experimental observations at low concentrations (up to 10(-6) M). Disagreement between the calculations and spectra recorded at higher concentrations (above 10(-5) M) shows that the reabsorbed light may be reemitted as fluorescence. The influence of inner-filter effects on the spectral shape was demonstrated by the experiments where a fibre-optic front-face fluorescence setup was applied: Under such conditions the shape of the fluorescence spectra for a high concentration (10(-3) M) coincided with that of a low concentration (10(-8) M). In conclusion, the present spectroscopic results show that AlPcS(4) does not form aggregates and is a very stable compound in aqueous solutions.     

Temperature effect on accumulation of protoporphyrin IX after topical application of 5-aminolevulinic acid and its methylester and hexylester derivatives in normal mouse skin

Significant amounts of protoporphyrin IX (PpIX) are formed after 6 min of topical application of 5-aminolevulinic acid (ALA) and its hexylester derivative, whereas PpIX is formed after 10 min of topical application of ALA-methylester derivative in normal mouse skin at 37 degrees C. Lowering the skin temperature to 28-32 degrees C by the administration of the anesthetic Hypnorm-Dormicum reduces the PpIX fluorescence by a factor of 2-3. Practically no PpIX was formed as long as the skin temperature was kept at 12-18 degrees C. At around 30 degrees C PpIX fluorescence appears later after application of ALA-ester derivatives (14-20 min) than after application of ALA (8 min), indicating differences in their bioavailability (delayed penetration through the stratum corneum, cellular uptake, conversion to ALA, PpIX production) in mouse skin in vivo. The difference in lag time in the PpIX formation after application of ALA and ALA-esters may be partly related to deesterification of the ALA-ester molecules. The temperature dependence of PpIX production may be used for improvement of photodynamic therapy with ALA and ALA-ester derivatives, where accumulation of PpIX can be selectively enhanced by increasing the temperature of the target tissue.     

Fractional Pais–Uhlenbeck Oscillator

In this paper we study the fractional Lagrangian of Pais–Uhlenbeck oscillator. We obtained the fractional Euler–Lagrangian equation of the system and then we studied the obtained Euler–Lagrangian equation numerically. The numerical study is based on the so-called Grünwald–Letnikov approach, which is power series expansion of the generating function (backward and forward difference) and it can be easy derived from the Grünwald–Letnikov definition of the fractional derivative. This approach is based on the fact, that Riemman–Liouville fractional derivative is equivalent to the Grünwald–Letnikov derivative for a wide class of the functions.     

The influence of UV exposure on 5-aminolevulinic acid-induced protoporphyrin IX production in skin.

The skin of nude mice was exposed to erythemogenic doses of UV radiation, which resulted in erythema with edema. An ointment containing 5-aminolevulinic acid (ALA) was topically applied on mouse and human skin. Differences in the kinetics of protoporphyrin accumulation were investigated in normal and UV-exposed skin. At 24 and 48 h after UV exposure, skin produced significantly less protoporphyrin IX (PpIX) than skin unexposed to UV. Human skin on body sites frequently exposed to solar radiation (the lower arm) also produced less PpIX than skin exposed more rarely to the sun (the upper arm). It is concluded that UV radiation introduces persisting changes in the skin, relevant to its capability of producing PpIX from ALA. The observed differences in ALA-induced PpIX fluorescence may be the result of altered penetration of ALA through the stratum corneum or altered metabolizing ability of normal and UV-exposed skin (or both).     

Gaussian integration of Chebyshev polynomials and analytic functions

Explicit bounds for the quadrature error of thenth Gauss-Legendre quadrature rule applied to themth Chebyshev polynomial are derived. They are precise up to the orderO(m ⁴ n ^–6). As an application, error constants for classes of functions which are analytic in the interior of an ellipse are estimated. The location of the maxima of the corresponding kernel function is investigated.Dedicated to Luigi Gatteschi on the occasion of his 70th birthday