SKIN DAMAGE IN ADULT AMPHIBIANS AFTER CHRONIC EXPOSURE TO ULTRAVIOLET RADIATION

Abstract— The effects of repeated UV exposure on the skin of the European crested newt, Triturus cristatus carnifex , have been investigated. The animals were irradiated 3 times per week with a Westing-house FS40T12 fluorescent sun lamp (wavelength spectrum 275–350 nm). Two groups of animals received the same total fluence of 1.3 × 10⁵ J/m² in single fluences of either 1570 J/m² (group A) or 9430 J/m² (group C), and one group received a total fluence of 2.6 × 10⁵ J/m² in single fluences of 4710 J/m² (group B). All the animals were killed 7 months after the first UV exposure, but at different intervals after the last exposure. Striking epidermal hyperplasia was found in the newts irradiated at the lower fluence rate (group A). In the animals given the higher total fluence (group B), the most prominent skin changes were dermal fibrosis and irregular thinning and thickening of the epidermis. No significant skin changes were found in group C., in which if there had been UV lesions, they had been repaired during the 5 month interval between the last irradiation and the killing of the animals. No skin tumors developed in any experimental group.     

Calorimetric study of the proximity effect in aliphatic diesters

Excess molar enthalpies,H ^E , at atmospheric pressure and 303.15 K are reported for binary mixtures of 1-chlorohexane with diethyl oxalate, diethyl malonate, diethyl succinate, diethyl glutarate, diethyl adipate, diethyl pimelate and diethyl sebacate. These experimental results, together with those obtained previously on the excess enthalpies of aliphatic diester+n-hexane mixtures, are interpreted in terms of molecular surface interactions between aliphatic, chlorinated and carboxylate groups. Comparison of the enthalpy interchange parameters reveals a decrease of the intermolecular interactions with decreasing intramolecular COO-COO distance in the diester molecule.

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Zusammenfassung Bei Atmosphärendruck und 303,15 K gemessene molare Überschußenthalpien (H ^E werden für binäre Gemische von 1-Chlorhexan mit Diäthyloxalat, Diäthylmalonat, Diäthylsuccinat, Diäthylglutarat, Diäthyladipat, Diäthylpimelat bzw. Diäthylsebacat angegeben. Diese experimentellen Ergebnisse werden zusammen mit den früher für Gemische von aliphatischen Diestern und n-Hexan erhaltenen Resultaten als molekulare Oberflächenwechselwirkungen zwischen aliphatischen, chlorierten und Carboxylatgruppen interpretiert. Ein Vergleich der Enthalpieaustauschparameter läßt eine Verminderung der intermolekularen Wechselwirkungen mit abnehmendem intramolekularem Abstand zwischen den COO-Gruppen erkennen.

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(H ^E ) 303,15 K 1- , , , , , . , + -, , . COO-COO .

     

Excess molar enthalpies at 298.15 K of (cyclohexane + a methylquinoline) and of (benzene + a methylquinoline)

Excess molar enthalpies of (cyclohexane or benzene + 2-methylquinoline, +4-methylquinoline, + 6-methylquinoline, + quinoline, + 1-methylnaphthalene, and + 2-methylnaphthalene) were measured at 298.15 K (the mixtures with 2-methylnaphthalene were studied at 309.15 and 318.15 K). From the results for (cyclohexane + a methylquinoline), all of which are strongly positive, it is possible to show that CH₃N interactions follow the expected order in accordance with the distance between the groups in the molecule. Measurements on (benzene + a methylquinoline) cannot be satisfactorily correlated with the dipole moment of the methylquinoline. The different activity of the methyl group in accordance with its position in the molecule accounts for the calorimetric behaviour of most of the mixtures.     

Development and validation of an ion pair HPLC method for gemcitabine and 2′,2′-difluoro-2′-deoxyuridine determination

A reverse phase HPLC method based on ion-pair formation was set up for the simultaneous determination of gemcitabine and its metabolite 2′,2′-difluoro-2′-deoxyuridine (dFdU) in plasma samples obtained from cancer patients. The separation was performed on a μBondapack C₁₈ (300 mm × 3.9 mm i.d., 10 μm particle size) column at room temperature. The mobile phase, 5 mM pentane-1-sulfonic acid pH 3.1/methanol (96:4), was pumped at a flow rate of 1.5 mL min⁻¹. Gemcitabine and dFdU eluted in less than 16 min. Linearity, sensitivity, and reproducibility studies, which actual values met the demands for bioanalytical assays, validated the method. This assay provided pharmacokinetic data from patients treated with intravenous gemcitabine.     

Solvent effects on internal conversions and intersystem crossings: the radiationless de-excitation of acrolein in water

An extended version of the averaged solvent electrostatic potential from molecular dynamics data (ASEP/MD) method oriented to the study of the solvent effects on internal conversion and intersystem crossing processes is presented. The method allows for the location of crossing points between free energy surfaces both in equilibrium and in frozen solvent conditions. The ground and excited states of the solute molecule are described at the complete active space self-consistent field (CASSCF) level while the solvent structure is obtained from molecular dynamics simulations. As an application, we studied the nonradiative de-excitation of s-trans-acrolein 1(n --> pi*) in aqueous solution. We found that the solvent modifies the relative stability of the different crossing points but not enough as to alter the relative order of stability with respect to the in vacuo situation. The relaxation through an equilibrium path involves a strong solvent reorganization. On the contrary, the nonequilibrium path does not involve solvent motion and the de-excitation could proceed with the same speed as in vacuo.     

Determination of Gemcitabine Triphosphate in Peripheral Blood Mononuclear Cells by Reverse-Phase HPLC

This paper describes a high-performance liquid chromatographic assay coupled with UV detection at 272 nm, to determine the levels of the nucleotide analogue gemcitabine triphosphate, one of the active metabolites of the antitumoral drug gemcitabine, in peripheral blood mononuclear cells. Isocratic ion-pair chromatography on a C₁₈ column was used. Samples were treated with trichloroacetic acid 40%, cleaned and neutralized with freon:trioctylamine (4:1). The method was linear on the concentration range tested, and the evaluated precision was found satisfactory (RSD < 6.8). The detection limit was 31 pmol, and the quantitation limit 102 pmol. The recovery of gemcitabine triphosphate ranged between 95 and 114%. The procedure was used to provide pharmacokinetic data from cancer patients treated with intravenous gemcitabine.