Using X-rays in photodynamic therapy: an overview

Photodynamic therapy is a therapeutic option to treat cancer and other diseases.

Photocatalytic conversion of gaseous nitrogen trichloride into available chlorine--experimental and modeling study

In water, chlorine reacts with nitrogen-containing compounds to produce disinfection byproducts such as nitrogen trichloride which induces ocular and respiratory irritations in swimming pool workers. A technical solution has been used to reduce NCl3 exposure to acceptable levels, by adding a stripping step to the water recycling loop. The pollutants extracted are currently rejected into the atmosphere without treatment. However, the physical properties of NCl3 could be harnessed to induce its controlled degradation by direct or indirect light. This paper describes the way to transform NCl3 into oxidizing chlorine by photocatalysis under laboratory conditions. Photocatalytic oxidation efficiently degrades gaseous nitrogen trichloride, producing compounds such as HClO. About 60% of NCl3 decomposed was converted into HClO which could be used as a disinfection compound. A kinetic model is proposed for the photocatalytic process based on a convection/diffusion model. The Langmuir-Hinshelwood model was applied to the chemical part of the mechanism. The apparent quantum yield was also estimated to assess the optimal irradiance for NCl3 transformation. The results show that photocatalysis performs much better than photolysis alone for NCl3 removal, i.e. at least 25 times more efficient.

From public to occupational health: towards an inverse push-pull paradigm in nanotechnologies innovation

Nanotechnologies are an important set of new technologies no longer at a very early stage in their development. The financial support for R&D in this domain is greater than a few Giga Euros/year for innovation and considerably lower (less than 1-2%) for risk management. At the factory level, As Low As Reasonably Achievable (ALARA) methods have to be used in order to protect workers against possible exposure. New "short-term" toxicological studies show that nano-particles are seldom exempt of effects in humans... Thus, for the general population, more and more anxious about the future, nanotechnologies are the object of numerous debates. Ultimately, the population is asking governmental bodies to take the required preventive measures. Social pressure is now initiated by the public towards innovative industries, which have to prove, before the marketing stage, the absence of any risk for the users and demonstrate a safety driven governance.

Hyalocyte-like cells are more numerous in the posterior chamber than they are in the vitreous of the rabbit eye

The distribution and concentration of free cells inside the eye chambers of rabbits were investigated using semi-quantitative analysis of histological paraffin sections. Studies using light (methacrylate sections) as well as transmission and scanning electron microscopy were undertaken for the morphological characterization of the free cells. Immunocytochemistry and autoradiography were employed in an attempt to find out their nature and their origin, respectively. It was observed that cells morphologically similar to the vitreous hyalocytes were more numerous inside the posterior chamber than were the hyalocytes in the cortical vitreous. Neither the hyalocytes nor the posterior-chamber cells reacted with an antibody to rabbit macrophages. The finding of labeled free cells after an intravitreal injection of 3H-thymidine indicates that these cells can renew themselves and that their number does not depend exclusively on monocytes migrating from the blood stream to the eye chambers, as is believed to occur. In conclusion, hyalocytes or hyalocyte-like cells are more concentrated in the posterior chamber than they are in the vitreous. Both the hyalocytes and the posterior-chamber cells could not be characterized as fully developed macrophages.

Membrane labelling by fluorescent probes: incorporation of TMA-DPH in erythrocyte membranes

A study of the labelling of isolated resealed erythrocyte membranes by TMA-DPH has been carried out. A quantitative study shows that saturation appears to take place when increasing the relative quantity of probe bulk concentration to membrane concentration; this is readily interpreted by a simple incorporation model with a limited number of sites in the membrane. A qualitative study shows that an increase in the labelling leads to an evolution of the probe fluorescence properties; the existence of different types of sites is involved in the interpretation but the system is too complex to allow it to be represented by a simple model. As a consequence of this study, care has to be taken in labelling biological material so as to avoid excessive probe incorporation.

Structure-dependent induction of bilirubin glucuronidation and lauric acid 12-hydroxylation by arylcarboxylic acids chemically related to clofibrate

The inductive potency of carboxylic acids, structurally related to clofibrate, on bilirubin UDPglucuronosyltransferase was investigated in the rat. For this purpose, structure-induction relationships were established using ten different arylcarboxylic or chlorophenoxycarboxylic acids. 4'-Chlorophenoxyacetic, -propionic and -isobutyric (clofibric) acids progressively increased hepatic glucuronidation of bilirubin (17%, 43%, 60% greater than controls, respectively) after a 5-day treatment in rat (100 mg/kg per day). 2-Phenylpropionic acid also enhanced bilirubin UDPglucuronosyltransferase activity (50%) in contrast to phenylacetic acid. The other compounds did not, or only slightly, affect this parameter. These results indicate that specific structural features are required for the induction property. Moreover, a good correlation (r = 0.962) was found between the extent of induction and the physiochemical descriptors which characterize the electronic state of the molecules, when analysed by multidimensional regression. Fluorescence polarization revealed that the compounds tested, especially clofibric acid, did not affect, in vivo or in vitro, the anisotropy of two different probes embedded in the microsomal membranes. Finally, since the interaction of the carboxylic acids with the membranes did not modify the latency state of bilirubin UDPglucuronosyltransferase, it was concluded that the increase in enzyme activity was due more to a real induction than to activation of bilirubin UDPglucuronosyltransferase. A close linkage was established between bilirubin UDPglucuronosyltransferase induction and that of cytochrome P-452, as shown by enhanced omega-oxidation of lauric acid. This led to the hypothesis that both processes could be under coordinate regulation and mediated by a molecular interaction depending on the physicochemical properties of the carboxylic acids.

Identification and quantitative determination of LSD by fluorescence: new data

Tests for the detection of lysergic acid diethylamide (LSD) are not always specific; to cope with this problem the authors have developed a fluorimetric apparatus and technique for the detection and identification of LSD in samples seized from illicit traffic in drugs. The fluorimeter is not electronic and is simple to make and use, inexpensive, easy to handle and suitable for field analyses. With the new, highly sensitive and selective method of synchronous excitation spectrofluorimetry, a toxicological analytical laboratory can confirm measurements made in the field and make an immediate determination of the quantity of LSD in the samples seized. The agreement between results obtained using differential fluorimetry or synchronous spectrofluorimetry and chromatographic techniques was found to be excellent. Quantitative analysis is very useful because the amount of LSD per "dose" can vary, from one batch to another, from a few tenths of a microgram to several hundred micrograms.

Structural changes of liver microsomes in rat during neonatal life: influence on the glucuronidation rates of various substrates

The Vmax of the membrane bound UDP-glucuronosyltransferase (UDP-GT) towards group 1 substrates (4-nitrophenol, 2-naphthol) was particularly higher in young rats than in adults. On the contrary, activity towards group 2 substrates such as borneol or testosterone was not detectable in fetus liver. The developmental pattern of UDP-GT was related to changes in lipid composition of microsomes, namely in the content in lysophosphatidylcholine which rose at birth. The phospholipid-cholesterol molar ratio also increased 2 fold from the 16th day of fetal life to the 4th day after birth. Measurement of the steady state anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) as well as determination of the order parameter S and the rotation cone angle of the fluorescent probe strongly suggested an increase in membrane fluidity in rat liver microsomes during ontogenesis.

Spectrofluorimetric methods for the measurement of the so called "microviscosity" of lipidic structures

The cellular interactions involving the membrane depend on its physico-chemical nature and on the topographical distribution of the membrane receptors. At present, the role of the lipidic regions is not well defined; however, it is known than the fluidity or "microviscosity" of the lipidic components controls important processes in cellular biology. Different spectrofluorimetric methods, continuous or time resolved, susceptible to the cohesion of lipidic regions have been developed: 1. The anisotropy of fluorescence where the rotation of probes is studied (linked to the coefficient of diffusional rotation). 2. The inhibition of fluorescence where the kinetics of the reaction is practically diffusion controlled. 3. The formation of emissive intramolecular complexes where the internal rotations of interchromophoric bonds are studied. After the development of kinetic models, the methods have been tested with synthetic and natural organized assemblies. The values of "microviscosity" obtained with these methods may be different because the environments of probes are different. Therefore, the concept of "microviscosity", applied to biological membranes is limited.

Mécanisme d'inhibition par des alcools de la photo-oxydation de l'heptanal en phase liquide

The photooxidation of heptaldehyde n-C6H13CHO can be inhibited by primary and secondary alcohols; this inhibition occurs through reaction between the peroxy radical C6H13CO3• and the alcohol, leading to less reactive species disappearing by recombination processes. Moreover, the reactivity of free radicals is modified by alcohols which solvate these radicals by hydrogen bonding. A kinetic scheme is proposed which accounts for the experimental results.