Memory processes in the response of plants to environmental signals.

Plants are sensitive to stimuli from the environment (e.g., wind, rain, contact, pricking, wounding). They usually respond to such stimuli by metabolic or morphogenetic changes. Sometimes the information corresponding to a stimulus may be "stored" in the plant where it remains inactive until a second stimulus "recalls" this information and finally allows it to take effect. Two experimental systems have proved especially useful in unravelling the main features of these memory-like processes.In the system based on Bidens seedlings, an asymmetrical treatment (e.g., pricking, or gently rubbing one of the seedling cotyledons) causes the cotyledonary buds to grow asymmetrically after release of apical dominance by decapitation of the seedlings. This information may be stored within the seedlings, without taking effect, for at least two weeks; then the information may be recalled by subjecting the seedlings to a second, appropriate, treatment that permits transduction of the signal into the final response (differential growth of the buds). Whilst storage is an irreversible, all-or-nothing process, recall is sensitive to a number of factors, including the intensity of these factors, and can readily be enabled or disabled. In consequence, it is possible to recall the stored message several times successively.In the system based on flax seedlings, stimulation such as manipulation stimulus, drought, wind, cold shock and radiation from a GSM telephone or from a 105 GHz Gunn oscillator, has no apparent effect. If, however, the seedlings are subjected at the same time to transient calcium depletion, numerous epidermal meristems form in their hypocotyls. When the calcium depletion treatment is applied a few days after the mechanical treatment, the time taken for the meristems to appear is increased by a number of days exactly equal to that between the application of the mechanical treatment and the beginning of the calcium depletion treatment. This means that a meristem-production information corresponding to the stimulation treatment has been stored in the plants, without any apparent effect, until the calcium depletion treatment recalls this information to allow it to take effect. Gel electrophoresis has shown that a few protein spots are changed (pI shift, appearance or disappearance of a spot) as a consequence of the application of the treatments that store or recall a meristem-production signal in flax seedlings. A SIMS investigation has revealed that the pI shift of one of these spots is probably due to protein phosphorylation. Modifications of the proteome have also been observed in Arabidopsis seedlings subjected to stimuli such as cold shock or radiation from a GSM telephone.

Reliability of respiratory symptoms to diagnose atopy.

As reliance of responses to epidemiological questionnaires on atopic symptoms is doubtful, we studied the predictive value of these questions relative to atopy, defined by the presence of serum specific IgE, taking into account some extraneous variables such as age and sex. The study population included 2067 adults, 20-60 years old. The protocol consisted of a standardized questionnaire and an evaluation of serum specific IgE using the Phadiatop (Pharmacia Diagnostics, Uppsala, Sweden) test. The predictive value of each symptom suggestive of atopy was quite low, but was much dependent on age and sex. Women more often than men reported atopic symptoms in the absence of atopy. Similarly, the predictive value of each symptom decreased with age. Thus atopic symptoms do not have the same value as predictors of atopy. These findings have both clinical and epidemiological important implications.

Atopy and systemic reactions to drugs.

To elucidate whether systemic reactions (SR) to drugs should be included in the atopic status in epidemiological studies, we compared the distribution of atopy in subjects with or without a history of SR to drugs. The studied population comprised 2067 adults, 20 to 60 years old, visiting a health care center for a check-up examination. The protocol included a questionnaire related to history of SR to drugs and a Phadiatop test which evaluates on a blood sample the presence of specific IgE against common aeroallergens. Overall, 14.7% of the study group, including 66% women, reported reliable histories of SR to drugs. The cumulative prevalence of asthma, hay fever and childhood dermatitis was higher in the SR group. By contrast, the percentage of positive Phadiatop tests was similar in subjects with or without a history of SR. Thus atopy, defined by an objective criterion, i.e. the presence of specific IgE against common aero-allergens, is not associated with the occurrence of SR to drugs. Such a history should not be included as part of the atopic status.

Prevalence of allergy to Hymenoptera stings.

In this study, we evaluated the prevalence of systemic reactions to hymenoptera stings in an adult general population, 20-60 years old. The protocol included a standardized questionnaire, skin tests to venom in subjects reporting a history of systemic reaction, and in subjects reporting a history of severe local and systemic reactions, as well as in a control group, a radioallergosorbent test (RAST) to hymenoptera venoms. According to the questionnaire, 1.2% of the study population had a history of systemic reactions. Only 0.85% had both such a history and a positive skin test to venoms. RASTs were positive, for at least one venom, in 57% of subjects with a history of systemic reaction, 15.8% of subjects with a history of severe local reactions, and 6.0% of the control group. In conclusion, this study shows that systemic reactions are not uncommon in the general population. RASTs tests are not sensitive or specific enough to be considered, per se, for indications of allergy to venoms.

[Allergy to Hymenoptera. Incidence and degree of public knowledge]. / Allergie aux hyménoptères. Fréquence et degré d'information du public.

The prevalence of systemic reactions to hymenoptera stings in adults is unknown. To elucidate this point we interviewed 2.067 persons aged from 20 to 60 years who attended a medical screening centre. We asked them whether they had ever experienced a reaction this kind, what they knew about it and what they did, and we performed skin tests to hymenoptera venoms in those who gave a positive answer. The proportion of subjects who had had at least one type of systemic reaction after being stung was 1.2 per cent; 0.9 per cent of the subjects had both a history of reaction and a positive skin test. This figure is in keeping with those obtained in surveys carried out among children, but is does not tally with the mortality figures which probably are grossly under-estimated. The general population is not adequately informed of possible systemic reactions to hymenoptera stings, so that people often fail to consult, and the practitioners themselves do not advise their patients to see an allergologist for evaluation. Thus, adequate information of the general population and the physicians is badly needed.