Endocrine regulation of trace element homeostasis in the rat

Conclusion The mechanisms responsible for the modifications of the concentrations of elements in tissues induced by hormonal influences are complex, because each hormone has pleiotropic actions that are sometimes opposite. Among these modifications, it is often difficult to distinguish between the adaptive defensive changes and the changes responsible for disorders or for exacerbating them, for example, Fe accumulation in tissues after HPX, TPTX, and castration. Moreover, in clinical conditions, hormonal disturbances are often enhanced by other defects, such as an excessive or a deficient intake of elements.     

Novel three-dimensional 1H−13C−31P triple resonance experiments for sequential backbone correlations in nucleic acids

Summary Backbone-driven assignment methods that utilize covalent connectivities have greatly facilitated spectral assignments of proteins. In nucleic acids, ¹H–¹³C–³¹P correlations could play a similar role, and several related experiments (HCP) have recently been presented for backbone-driven sequential assignments in RNA. The three-dimensional extension of ¹H–³¹P Het-Cor (P,H-COSY-H,C-HMQC) and Het-TOCSY (P,H-TOCSY-H,C-HMQC) experiments presented here complements HCP experiments as tools for spectral assignments and extraction of dihydral angle constraints. By relying on ¹H–³¹P rather than ¹³C–³¹P couplings to generate cross peaks, the strongest connectivities are observed in different spectral regions, increasing the likelihood of resolving spectral overlap. In addition, semiquantitative estimates of ¹H–³¹P and ¹³C–³¹P couplings provide dihedral angle constraints for RNA structure determination.     

Rapid and sensitive high-performance liquid chromatographic analysis of halogenopyrimidines in plasma

Recent studies have stressed the need for individual adjustment of 5-fluorouracil (5-FU) dosage. Most of the techniques previously reported are not well adapted to routine application. We describe a sensitive, selective and simple HPLC technique under isocratic conditions for the quantitation of 5-FU and other halogenopyrimidines. The proportion of reagents and internal standard were optimised to allow the use of minitubes, particularly adapted to large series of plasma assays. High extraction yield, 75% for 5-FU and 90% for 5-bromouracil and 5-chlorouracil, was obtained using 1.2 ml isopropanol–ethyl acetate (15:85, v/v) following precipitation of plasma proteins with 300 mg ammonium sulfate. The mobile phase was 0.01 M phosphate buffer (pH 3.0). Uracil and 5-fluorouracil were fully resolved with Spherisorb ODS2 column. The limits of quantitation and detection in human plasma were 6 ng ml⁻¹ and 3 ng ml⁻¹, respectively, for all compounds studied. The total analysis time required for each run was 25 min. Final results could be given within 90 min of blood sampling. At least 50 plasma samples could be analysed per day. This method has been successfully used for monitoring 5-FU-based treatments.     

Endothelial cell junctions

In the course of a freeze-cleave study on intercellular junctions in the regenerating rat liver, we observed an unusual array of intramembranous particles located in regions of contact between endothelial cells lining the hepatic sinusoids. These arrays were characterized by an accumulation of particles which resembled a zonula occludens in their linear deployment but differed in that the contact regions were composed of individual particles which remained separated from each other by regular particle-free intervals.     

Effect of ascorbic acid during acute iterative anoxia, hypothesis of an anti-oxidizing mechanism of action in comparison with the effect of hydroquinone

Some of the problems which appear during senescence, are said to be caused by cerebral oxygen deficiency and various experiments have been set up to try to imitate this particular aspect of the ageing process. We have already studied the action of many drugs with regard to acute repeated anoxia. Our work has given us clear evidence of the activity of ascorbic acid, which delays the moment of electroencephalographic silence in rats and decreases the latent period up to the reappearance of electrical activity. In order to pinpoint the mechanism of action, we compared the influence of lysine aceto-salicylate with that of hydroquinone. Very small doses of the latter drug produce a marked effect and lead us to put forward the hypothesis that it may be anti-oxydising. However, although all the drugs which proved effective in these experiments may be grouped together (despite their varying pharmacological profiles) and described as "anabiotic" drugs, it is not possible to revert to a single mechanism of action for the group as a whole.