Tree root dynamics in montane and sub-alpine mixed forest patches.

Background and Aims: The structure of heterogeneous forests has consequences for their biophysical environment. Variations in the local climate significantly affect tree physiological processes. We hypothesize that forest structure also alters tree root elongation and longevity through temporal and spatial variations in soil temperature and water potential. Methods: We installed rhizotrons in paired vegetation communities of closed forest (tree islands) and open patches (canopy gaps), along a soil temperature gradient (elevations of 1400, 1700 and 2000 m) in a heterogeneous mixed forest. We measured the number of growing tree roots, elongation and mortality every month over 4 years. Key Results: The results showed that the mean daily root elongation rate (RER) was not correlated with soil water potential but was significantly and positively correlated with soil temperature between 0 and 8 °C only. The RER peaked in spring, and a smaller peak was usually observed in the autumn. Root longevity was dependent on altitude and the season in which roots were initiated, and root diameter was a significant factor explaining much of the variability observed. The finest roots usually grew faster and had a higher risk of mortality in gaps than in closed forest. At 2000 m, the finest roots had a higher risk of mortality compared with the lower altitudes. Conclusions: The RER was largely driven by soil temperature and was lower in cold soils. At the treeline, ephemeral fine roots were more numerous, probably in order to compensate for the shorter growing season. Differences in soil climate and root dynamics between gaps and closed forest were marked at 1400 and 1700 m, but not at 2000 m, where canopy cover was more sparse. Therefore, heterogeneous forest structure and situation play a significant role in determining root demography in temperate, montane forests, mostly through impacts on soil temperature.

[Nitric oxide: a different kind of gas]. / Le monoxyde d'azote: un gaz pas comme les autres.

Nitric oxide (NO), the first gas to obtain temporary approval for use in medicine, is regulated in private and public health care facilities by the supply, prescription and dispensing rules applied for drugs with special modalities controlling its administration. This apparently simple gas which diffuses easily from one cell to another is actually very complex in its form and reactivity, making it an unconventional messenger. The life time of a molecule is very short. NO is synthesized and released continuously. Its direct or mediated vasodilator effect has led to four temporary approval rulings validated again in 1997 by the national health authorities.

Study protocol: stability of morphine injected without preservative, delivered with a disposable infusion device.

BACKGROUND AND OBJECTIVE: Morphine hydrochloride, a major analgesic drug, is being increasingly administered using portable disposable infusion devices. The objective of this study was to investigate the stability of morphine in such a system at two concentrations (2.50 and 5.00 mg/ ml) over a 30-day period. METHOD: High-performance liquid chromatography of stored morphine solutions. RESULTS: The best stability was observed with disposable infusion devices filled with a morphine solution containing sodium metabisulphite as a preservative. No breakdown products were detected after 1 month of storage at room temperature, in light or darkness. On the other hand, 2.50 and 5.00 mg/ml morphine solutions without sodium metabisulphite, stored in the infusion device led to the formation of 0.205% and 0.235% of pseudomorphine, respectively, after 6 days of storage in the light, and 1.50% and 0.94% after 30 days storage. CONCLUSION: Morphine hydrochloride solutions stored in disposable infusion devices degraded very slowly, particularly when preserved with sodium metabisulphite. The solutions are stable over 5 days, the maximum period of storage normally required when using disposable infusers.

[Ecstasy: psychostimulant, hallucinogen and toxic substance]. / L'ecstasy: psychostimulant, hallucinogène et toxique.

MDMA or 3,4-methylenedioxymethamphetamine, more commonly called "ecstasy", is a drug classified as a stupefiant and increasingly used by young people for its stimulant and hallucinogen effects. This popular designer drug is often used in techno or rave parties and perceived by users as relatively harmless. It has however been associated with disorders of thermoregulation and has been the cause of several deaths. In addition, the drug has been shown to destroy serotonin receptors in the brain in the monkey and leads to serious physchiatric disorders and liver damage in man.

[Aluminum, hypothetic cause of Alzheimer disease]. / L'aluminium, cause hypothétique de la maladie d'Alzheimer.

A great deal of research has focused on aluminium as a putative causative factor in Alzheimer's disease. We measured by atomic absorption spectrophotometry aluminium levels in blood, urine and cerebrospinal fluid from 15 patients with Alzheimer's disease, compared with 20 control individuals. There were no statistically significant differences between the two groups. This suggests that aluminium is not a causative factor for Alzheimer's disease.

New calibration method for gas chromatographic assay of carbon monoxide in blood.

The calibration method described is based on the in situ formation of carbon monoxide in a closed system by the reaction of hot concentrated sulfuric acid with formic acid. Carbon monoxide is released from hemoglobin by treatment with 85% phosphoric acid, diluted 1:2 (v/v). Carbon monoxide is analyzed by means of headspace gas chromatography on a Porapak Q 80-100 column, following catalytic reduction to methane, using a flame-ionization detector. The method was validated by comparing the results obtained for blood samples from patients suffering from carbon monoxide poisoning and previously analyzed by means of spectrophotometry.

Urinary 5 alpha-androstane-3 alpha, 17 beta-diol (5-Ad) determination in healthy children and adults.

The authors suggest a method for the evaluation of the urinary 5 alpha-androstane-3 alpha, 17 beta-diol (5 Ad) carried out by gas-liquid chromatography. 5-Ad is separated from its isomers, first by means of an adsorption chromatography on alumina and then by means of a high performance liquid chromatography on porous silica. The reliability criteria of the method have been studied according to the advice of the French Society of Clinical Biology. This method, applied to 175 healthy individuals of both sexes, grouped according to age starting from three years, allowed to determine the usual values of urinary excretion of 5-Ad in relation to age.

[Breast-feeding and oral contraceptives].

PIP: After briefly describing the mechanisms of lactation and of oral contraception and the composition and chemical structure of the drugs used, the possible effects of oral contraceptive treatment during breast-feeding on the nutritional value of the milk and the duration of lactation, as well as on the child fed by the milk, are considered. The available information is limited and it is difficult to extrapolate findings from animal tests to determine possible effects on man, but, on the basis of animal studies and observation of human subjects, it is recommended that extreme caution be ued in the use of oral contraceptives during breast-feeding and, if possible, the selection of other contraceptive methods. It is pointed out that the amount of drugs that passes into the milk constitutes a relatively high therapeutic dose for a child weighing 3-4 kg and consuming 600 ml to 1l of milk daily for prolonged periods.^ieng