Skin photosensitization with topical hypericin in hairless mice

Hypericin, a naturally occurring photosensitizer, exhibits interesting in vitro photobiological activities, which suggest that the compound is a potential antipsoriatic agent. In this study, the possibility of hypericin penetrating the skin in photo-active concentrations has been studied. Hypericin is incorporated in either emulsifying ointment supplemented with solketal (hypericin content: 0.05%) or in polyethylene glycol (PEG) ointment (hypericin content: 0.5%) and applied to the skin of hairless mice for 4 h. After removing excess ointment, the mice are then irradiated with different light doses using a 500 W halogen lamp. As a positive control, intraperitoneally (i.p.) administered hypericin (10 and 40 mg/kg) has also been tested. Erythema, desquamation and erosions are demonstrated in the mice treated with hypericin in emulsifying ointment with solketal using a light dose of at least 4.5 J/cm2. In general, these reactions correlate well with those of i.p. administered hypericin (40 mg/kg), indicating that hypericin incorporated in emulsifying ointment with solketal is well absorbed by the skin of the mice. However, for the i.p. administered hypericin (40 mg/kg), we could not evaluate phototoxic reactions in the group of animals that received a light dose of 108 J/cm2, as they all died 12-24 h after irradiation, indicating extreme photosensitization with systemic hypericin at higher light doses. On the contrary, there is no measurable skin photosensitivity induced by hypericin when incorporated in PEG ointment or when 10 mg/kg hypericin is i.p. administered. Our results show that hypericin incorporated in a suitable vehicle can be delivered to the skin in photo-active concentrations. Using a vehicle such as emulsifying ointment with solketal, it will be possible to explore the photo-activity of hypericin in the treatment of psoriasis and other skin diseases.     

Dietary beta-carotene and 13-cis-retinoic acid are not effective in preventing some features of UVB-induced dermal damage in hairless mice

Albino hairless mice were fed diets containing 10 g/kg feed of beta-carotene and 200 mg/kg feed of 13-cis retinoic acid to assess the ability of these molecules to prevent UVB-induced dermal damage. Diets were administered for 12 weeks prior to UVB exposure and were continued throughout the 20 week irradiation period. The UVB source was a bank of FS-20 sunlamps (280-400 nm: peak 313 nm). Exposures were thrice weekly at 0.1 J/cm2 per exposure for the first 10 weeks and 0.2 J/cm2 per exposure for the second 10 weeks. Histologic evaluation of skin biopsies revealed no difference, between animals fed active or placebo diets, in UVB-induced elastosis, collagen changes or amounts of glycosaminoglycans and proteoglycans of the ground substance.     

Effect on topical 5-methoxypsoralen on tumorigenesis induced in albino and pigmented hairless mouse skin by UV irradiation

A new line of the Skh:HRII hairless pigmented mouse (black juvenile coat) is described which has been selectively bred for the capacity to respond consistently to simulated solar UV radiation with a continuous and strong tan. This mouse demonstrates a degree of protection from chronic UV-induced tumorigenesis when compared with the Skh:HRI hairless albino mouse, and has been used here to study the effect of induced melanogenesis on phototumorigenesis. Mice were irradiated for 10 weeks with incremental doses of simulated solar UV radiation (UVA + B) from a fluorescent tube source which induced tumours in 100% of albino mice and 93% of black mice by 200 days (minimally oedemal), or with 60% of this dose (sub-oedemal) which induced tumours in 85% of albino mice and 65% of black mice. Mice were also exposed to the UVA component of these radiation sources, obtained by window glass filtration. The effect of topical 5-methoxypsoralen (5-MOP) was examined, at either 0.003% with minimally oedemal UVA + B or its UVA component alone, or at 0.01% with sub-oedemal UVA + B or its UVA component alone, in both albino and black mice. The 5-MOP concentrations were selected as the maximum concentration which did not increase the erythema and oedema responses after a single exposure to minimally oedemal or sub-oedemal UVA + B. At 200 days, the tumorigenic response to sub-oedemal UVA + B was significantly increased by topical 5-MOP, to 100% in albinos and 93% in black mice. In contrast, tumorigenesis in response to minimally oedemal UVA + B was unaffected by topical 5-MOP. The UVA component alone of either irradiation regime was not tumorigenic under these conditions. When combined with topical 5-MOP, the UVA of minimally oedemal UVA + B became moderately tumorigenic, and resulted in a tumour incidence of 23% in albinos and 14.5% in black mice. However, the UVA component of sub-oedemal UVA + B, when combined with topical 5-MOP, was highly tumorigenic specifically in albino mice, inducing tumours in 93% of albino mice but in only 27% of black mice. Tan intensity resulting from minimally oedemal UVA + B was not enhanced by topical 5-MOP, and its UVA component combined with 5-MOP resulted in only a minimal tan. However, the tan intensity resulting from sub-oedemal UVA + B with topical 5-MOP was strongly increased, although its UVA component combined with 5-MOP did not produce a perceptible tan.(ABSTRACT TRUNCATED AT 400 WORDS)     

Chronic ultraviolet B radiation-induced biochemical changes in the skin of hairless mice

Skh:HR-1 hairless mice were irradiated chronically with sub-erythemal doses of UVB radiation, and a number of biochemical parameters in the skin were determined after 6, 12, 18, and 24 wk of exposure. The parameters measured were water, collagen, elastin, and glycosaminoglycan content; collagenase and elastase levels; and Bz-Tyr-OEt (N-benzoyl-L-tyrosine ethyl ester) and BAPNA (alpha-N-benzoyl-DL-arginine-p-nitroanilide) hydrolyzing activities. Data for UVB radiation-exposed and chronological age-matched control mice were compared with respect to unit area and to unit mass of skin. On a unit area of skin basis, UVB radiation exposure increased the level of most parameters. The particular exceptions were collagen and collagenase which remained constant. On a mass of skin basis, though, there is an apparent decrease in collagen content because of the increase in the other skin components. This suggests that there is insufficient collagen in UVB radiation-exposed skin to support the increasing mass of the tissue.     

Why delta-valerolactone polymerizes and gamma-butyrolactone does not

gamma-Butyrolactone, unlike delta-valerolactone, does not polymerize despite a strain energy of approximately 8 kcal mol-1 which could be relieved by opening the s-cis lactone ester bond to an s-trans ester bond in the polymer. To explain this anomaly, we have applied quantum mechanical methods to study the thermochemistry involved in the ring-opening reactions of gamma-butyrolactone and delta-valerolactone, the conformational preferences of model molecules that mimic their corresponding homopolyesters, and the variation of enthalpy associated to the polymerizability of such two cyclic lactones. The overall results indicate that the lack of polymerizability of gamma-butyrolactone should be attributed to the low strain of the ring, which shows much less geometric distortion in the ester group than delta-valerolactone, and the notable stability of the coiled conformations found in model compounds of poly-4-hydroxybutyrate.     

The metal rhodium does not have allotropes

The synthesis of the three ¹⁸F-labeled 2-nitroimidazoyl oximes is described to be used as possible hypoxia tumor imaging agents. The title oximes were successfully synthesized in a four step sequence, characterized, and finally radiolabeled. Under optimized labeling conditions, the radiochemical yields of the three markers were in the range of 69–80%.     

UVA- and UVB-induced changes in collagen and fibronectin biosynthesis in the skin of hairless mice.

The modifications induced in hairless mouse skin by chronic UV irradiation were investigated. Skin explant cultures were used to study UVA- and UVB-induced changes occurring in interstitial collagen (type I and type III) and fibronectin biosynthesis. To study the long-term effects, albino hairless mice were irradiated with UVA radiation alone from two sources with different spectral qualities or with UVB. UVA and UVB radiation produced a significant increase in the ratio of type III to type I collagen (more than 100% for UVA-irradiated skin and about 60% for UVB-irradiated skin) accompanied by a significantly increased fibronectin biosynthesis (50% or more in all irradiated groups). Irradiation with either UVA or UVB alone had no significant effect on the total collagen synthesis and resulted in only a slight decrease in the total collagen content of the skin determined as hydroxyproline. This decrease was significant only in the case of the group irradiated with UVA (xenon) (decrease of 25%, expressed as micrograms of hydroxyproline per milligram wet weight). A significant decrease in collagen hydroxylation (expressed as radioactive hydroxyproline/radioactive hydroxyproline plus proline in neosynthesized collagen) was observed of about 50% in skin irradiated with UVA (xenon) but not in UVB-treated skin. Several of the above modifications (increased fibronectin biosynthesis, increased collagen type III to type I ratio) correspond to the modifications observed during the aging of non-irradiated hairless mice. Therefore it appears that UV irradiation accelerates the modifications of extracellular matrix biosynthesis observed during aging.     

The dynamic crossover in water does not require bulk water

Many of the anomalous properties of water may be explained by invoking a second critical point that terminates the coexistence line between the low- and high-density amorphous states in the liquid. Direct experimental evidence of this point, and the associated polyamorphic liquid-liquid transition, is elusive as it is necessary for liquid water to be cooled below its homogeneous-nucleation temperature. To avoid crystallization, water in the eutectic LiCl solution has been studied but then it is generally considered that "bulk" water cannot be present. However, recent computational and experimental studies observe cooperative hydration in which case it is possible that sufficient hydrogen-bonded water is present for the essential characteristics of water to be preserved. For femtosecond optical Kerr-effect and nuclear magnetic resonance measurements, we observe in each case a fractional Stokes-Einstein relation with evidence of the dynamic crossover appearing near 220 K and 250 K respectively. Spectra obtained in the glass state also confirm the complex nature of the hydrogen-bonding modes reported for neat room-temperature water and support predictions of anomalous diffusion due to "worm-hole" structure.     

Matrix effect in second-order data: determination of dyes in a tanning process using vegetable tanning agents

The aim of this paper is to determine the concentration of three dyes throughout the tanning process of leather using vegetable tanning agents with a sequential injection analyser with second-order data treatment. As the vegetable tanning agents used are highly absorbent species, we focus on three aspects: (i) difficulties with the resolution (ii) the reduction in the working concentration range; and (iii) matrix effects. Ideally, second-order instruments provide “second-order advantage”; i.e. calibration is possible in the presence of uncalibrated interfering species. However, if the interfering species change the instrumental response of the analyte (in scale or shape), standard additions must be used to ensure the accuracy of the estimated analyte concentration. Here we study the presence of matrix effects for three dyes in several samples in order to significantly improve the accuracy of predictions in the presence of such effects. We found that there were matrix effects in at least 80% of the samples with an alpha risk of 5%. We used this method to study the exhaustion of dyes in the dyeing process.     

Self-assembly does not account for the hydrophobic effect

Marmur has claimed that large values of activity coefficients for nonelectrolytes, particularly in the context of hydrophobic interactions between solutes in aqueous solution at ambient temperature and pressure, cannot be accounted for by thermodynamics, and has suggested that association (self-assembly) of solute molecules in solution solves this dilemma. We show that the analysis of Marmur is incorrect, specifically because the equilibrium in solution between monomeric solute molecules and associated solute molecules is entirely ignored. We show further that activity coefficients such as that for nitromethane solute in hexane solvent, 39.7, and that for solute hexane in solvent water, 4.48 x 10(5), can be calculated as 31.9 and 4.71 x 10(5), respectively, by methods based on well-known molecule-molecule interactions. No assumption of self-assembly is required.     

Absence of photoreactivation of pyrimidine dimers in the epidermis of hairless mice following exposures to ultraviolet light

Abstract—The influence of photoreactivating light on the fate of UV-induced DNA damage has been measured in the epidermis of hairless mice using damage-specific endonuclease from Micrococcus luteus. Groups of mice were exposed to varying fluences of UV at 297nm or from an FS40 fluorescent sun lamp to induce UV photoproducts. The same fluence-dependent DNA damage was observed in high molecular weight epidermal DNA regardless of whether the mice were killed immediately, or maintained in the dark or under photoreactivating light for 20 h after UV. Thus, no detectable photoreactivation of UV-induced pyrimidine dimers could be demonstrated in mouse epithelial cells in vivo.     

Why tert-butyl alcohol associates in aqueous solution but trimethylamine-N-oxide does not

In dilute aqueous solution, tert-butyl alcohol (TBA) tends to aggregate but trimethylamine-N-oxide (TMAO) does not. Given that both molecules have very similar geometry with hydrophobic and hydrophilic groups, it is interesting to ask why they behave so differently in aqueous solution. To explore this question, we use molecular dynamics simulations to study two models representing TBA and TMAO that differ essentially only in their electrostatic properties. It is shown that this difference is sufficient to give the different solution behavior. Furthermore, the principal difference identified is that the hydrophilic group of TMAO (the oxygen) interacts on average much more strongly with water than the corresponding group (the hydroxyl) of TBA. A hydrogen-bond analysis shows that water-TBA and water-TMAO hydrogen bonds are similar in number, but that the hydrogen-bond energy is much more negative for water-TMAO. In all likelihood, this accounts for the different behavior in dilute aqueous solution.     

Beta-carotene does not act as an optical filter in skin.

Beta-carotene, when orally administered, only slightly increases the sunburn threshold in normal humans but effectively diminishes sunlight risk in patients suffering from erythropoietic protoporphyria. In addition, beta-carotene has been shown to inhibit UV-induced carcinogenesis in mice when administered either orally or intraperitoneally. To examine the photoprotective properties of beta-carotene, SKH-HR1 albino hairless mice received beta-carotene supplemented diets for either two or four weeks. At the end of each treatment period the skins were visibly yellow. Whole skin and epidermis from each animal were studied by forward scattering transmission spectroscopy and compared with age-matched controls. While no major optical differences were seen in the whole skin or in the epidermis, the presence of beta-carotene was optically demonstrated by weak but typical beta-carotene absorption peaks in the epidermis following the two week feeding period. The peaks were also apparent in the four week group. However, the beta-carotene peaks could not be resolved through full thickness skin. Despite the yellow appearance of the skin, the absorbance due to the carotene was insufficient to impart significant photoprotection. These results confirm previous theoretical arguments that oral beta-carotene treatment does not attain a sufficient concentration in the skin to produce a typical sunscreen effect by absorption of radiation. When beta-carotene is effective in the treatment of photosensitivity, it must produce its protectiveness through an alternative mechanism.     

Super-washing does not leave single walled carbon nanotubes iron-free

We demonstrate with transmission electron microscopy and X-ray photoelectron spectroscopy that single-walled carbon nanotubes contain significant amounts of iron in the form of Fe(3)O(4), which even after acid washing, is not removed.     

End-grafted low-molecular-weight PNIPAM does not collapse above the LCST

The interfacial properties of end-grafted temperature-responsive poly(N-isopropylacryamide) (PNIPAM) were quantified by direct force measurements both above and below the lower critical solution temperature (LCST) of 32 degrees C. The forces were measured between identical, opposing PNIPAM films and between a PNIPAM film and a lipid membrane. At the grafting densities and molecular weights investigated, the polymer extension did not change significantly above the LCST, and the polymers did not adhere. Below the LCST, the force-distance profiles suggest a vertical phase separation, which results in a diluter outer layer and a dense surface proximal layer. At large separations, the force profiles agree qualitatively with simple polymer theory but deviate at small separations. Importantly, at these low grafting densities and molecular weights, the end-grafted PNIPAM does not collapse above the LCST. This finding has direct implications for triggering liposomal drug release with end-grafted PNIPAM, but it increases the temperature range where these short PNIPAM chains function as steric stabilizers.     

Intramolecular charge transfer in 4-aminobenzonitriles does not necessarily need the twist

In electron donor/acceptor species such as 4-(dimethylamino)benzonitrile (DMABN), the excitation to the S(2) state is followed by internal conversion to the locally excited (LE) state. Dual fluorescence then becomes possible from both the LE and the twisted intramolecular charge-transfer (TICT) states. A detailed mechanism for the ICT of DMABN and 4-aminobenzonitrile (ABN) is presented in this work. The two emitting S(1) species are adiabatically linked along the amino torsion reaction coordinate. However, the S(2)/S(1) CT-LE radiationless decay occurs via an extended conical intersection "seam" that runs almost parallel to this torsional coordinate. At the lowest energy point on this conical intersection seam, the amino group is untwisted; however, the seam is accessible for a large range of torsional angles. Thus, the S(1) LE-TICT equilibration and dual fluorescence will be controlled by (a) the S(1) torsional reaction path and (b) the position along the amino group twist coordinate where the S(2)/S(1) CT-LE radiationless decay occurs. For DMABN, population of LE and TICT can occur because the two species have similar stabilities. However, in ABN, the equilibrium lies in favor of LE, as a TICT state was found at much higher energy with a low reaction barrier toward LE. This explains why dual fluorescence cannot be observed in ABN. The S(1)-->S(0) deactivation channel accessible from the LE state was also studied.     

A self-assembled framework that interpenetrates in crystal but does not interpenetrate in solution

A porous supramolecular framework has been for the first time revealed to undergo interpenetration in crystal and noninterpenetration in solution. A new supramolecular organic framework Bu-SOF has been constructed from the co-assembly of a tetracationic tetrahedral monomer and cucurbit[8]uril(CB[8]) in water through the encapsulation of two anti-parallel n-butyl chains by CB[8]. X-ray diffraction analysis reveals that Bu-SOF forms 3-fold interpenetrated networks in crystals grown by evaporation of its solution in water.1 H NMR, dynamic light scattering and isothermal titration calorimetric experiments confirm that Bu-SOF is also formed in water. Solid samples, prepared by lyophilizing the aqueous solution of Bu-SOF, can adsorb nanoscaled organic dyes, supporting the porosity of the framework and thus non-interpenetration in solution. The avoidance of interpenetration of Bu-SOF in solution has been attributed to the filling of water inside the porous framework as well as the electrostatic repulsion of the appended bipyridinium units of the tetrahedral building block.     

Orbital-optimized coupled-cluster theory does not reproduce the full configuration-interaction limit

It is shown that due to the mixing of the usual projection approach of coupled cluster with variational orbital optimization, orbital-optimized coupled cluster (OCC) fails to reproduce the full configuration-interaction (full CI) limit when the cluster operator becomes complete. It is pointed out that the fulfillment of the projected singles equations, which define the orbital gradient in Brueckner coupled cluster (BCC), is mandatory for a correct behavior. As numerical examples we present general OCC and BCC calculations up to the full CI limit on CH(2) and an active-space model of ozone. The observed deviations of OCC from full CI are of the order of the correlation error obtained in calculations with up to quadruples excitations. Thus the failure of OCC may be considered tolerable in more approximate calculations but clearly prohibitive for any benchmark application. For applications to active-space models a hybrid approach for OCC is suggested in which for active particle-hole rotations the Brueckner orbital gradient is employed, whereas for the remaining orbital rotations the variational orbital gradient is retained.