The aim of our study was the evaluation of contact sensitization in pediatric patients with atopic dermatitis (AD). It seems that the frequency of contact allergies in the course of AD, and also the frequency of contact allergies in children, is underestimated in general. Our study has been performed by investigating 137 children with AD. The childrens' history was taken according standardized consultation guidelines and followed by a physical examination. Patch testing was performed systematically, including the European standard series, together with tixocortol pivalate, budesonide and the applied emollient. If necessary, optional patch tests were performed according to the child's history. The results demonstrate contact sensitization in 43% of all children tested. The most frequent contact allergens are: metals (19.3%), fragrance (4.4%), balsam of Peru (2.6%), lanolin (4.4%), neomycin (2.6%) and emollients (2.6%). No contact sensitization to corticosteroids nor any induction of active sensitization were seen. Statistical analysis demonstrates that the risk of developing a contact allergy is significantly elevated in children after the age of 5 years. Female sex is a risk factor only for nickel. Age of onset of AD or its severity is not associated with the development of contact allergy. In conclusion, the results indicate the necessity of performing systematic patch testing in the investigation of allergies in children with AD. Preventive measures from an early age are suggested to avoid exposure to the most frequent contact allergens.

A metabolite extracted from maize culture was identified as cyclonerodiol. Its 1H and 13C NMR spectra have been fully analysed, and some literature assignments have been reversed.

Trunk phloem necrosis (TPN) of Hevea brasiliensis is an irreversible syndrome of the phloem that spreads from the collar towards the tapping cut. It is responsible for the cessation of latex production, the main constraint in rubber plantations worldwide. Numerous investigations have been undertaken to understand the mechanisms of this disease. The apparent linear spread of TPN supported the initial hypothesis of a biotic causal agent for TPN. However, previous and recent aetiological analyses remained inconclusive and the pathogen hypothesis is tending to be abandoned. In this paper we present a complementary statistical analysis of spatio-temporal epidemiological data collected in a rubber plantation in Cô te d'Ivoire. There, four study plots were surveyed each year from 2000 to 2003, with tree-by-tree disease assessment. In two plots, the tapping knife was systematically disinfected with sodium hypochlorite to stop any virus or viroid transmission. Based on permutation tests, our analysis confirmed the aetiological results: there was no evidence for spread by pathogen transmission. However, the spatial structure of the disease was clear. These results strengthen the current alternative scenario of a multi-factor physiological disease caused by an accumulation of exogenous and endogenous stresses. Spatial heterogeneity of the risk factors probably results in the presence of areas of stress that can explain the spatial patterns observed among the TPN cases. The final contribution of this study was confirmation of the curative effect of sodium hypochlorite in the earliest stages of the disease, thus opening the way for control of this disease.

The main constraint in rubber plantations worldwide is the cessation of latex production because of two syndromes: (i) tapping panel dryness (TPD), a reversible physiological response to overexploitation; and (ii) bark necrosis (BN), an irreversible syndrome spreading from the collar toward the tapping cut. Early BN symptoms develop in the inner phloem tissues but never affect the cambium. Necrotic patches appear in the outer phloem, inducing bark cracking and peeling, but these alterations never lead to tree death. BN spreads gradually to neighboring rubber trees, and evidence of linear disease centers suggest that a pathogen may be involved, possibly transmitted by the tapping knife. Several previous etiological investigations (fungi, phytoplasma, bacteria, and virus) were performed (3) on leaves, bark, and latex using different methods (e.g., isolation, transmission, chemical treatments, and optic and electron microscope studies). Recent works focused on mechanically transmissible pathogens, such as viroid (2) or virus/double strand RNA, using RNA extraction (nonionic cellulose and appropriate ethanol concentrations) and treatment with RNase A, followed with sequential polyacrylamide gel electrophoresis (s-PAGE), reverse transcription-polymerase chain reaction (RT-PCR), degenerate oligonucleotide primer-PCR (DOP-PCR), and cloning and sequence analysis. While numerous viroid-like (between 250 and 400 nucleotides) and double strand virus-like (1,800 bp) low-molecular-weight RNAs were observed, no definite correlation was found with the BN status of trees. Sequencing of the various isolated RNAs only identified plasmids, nonpathogenic bacteria and yeasts, but none of the suspected pathogens. In addition, previous and recent transmission trials (tapping knife disinfection, bud grafting, bark implantation, and etc.) failed to confirm the involvement of a biotic agent. In conclusion, since these etiological investigations were inconclusive, a physiological disease is now suspected that involves exogenous stresses, nonoptimal vascular relations at the rootstock/scion junction and impaired cyanide metabolism (1,4). References: (1) H. Chrestin et al. Plant Dis. 88:1047, 2004. (2) N. Duran-Vila et al. J. Gen. Virol. 69:3069, 1988. (3) D. Nandris et al. Eur. J. For. Pathol. 21:340, 1991. (4) D. Nandris et al. Plant Dis. 88:1047, 2004.

Bark necrosis (BN), described and first studied in Côte d'Ivoire in the 1980s (2), affects most modern rubber plantations (i.e., grafted trees with high-yielding clones, intensive exploitation due to tapping frequency, and use of Ethrel as a yield stimulant) worldwide with a wide range of severity across sites. While previous (3) and recent (4) etiological analyses remain inconclusive, environmental factors were shown associated with BN. Numerous epidemiological surveys conducted in various African and Asian plantations on recently tapped blocks (less than 10-year-old trees) revealed the nonrandom location of the earliest single diseased trees. These risky areas are mainly characterized by the proximity of a swamp, plantation road, windrow, old bulldozer track, residual forest stump, or slope break. In BN emergence areas, while no significant correlation was found with chemical soil parameters, physical soil analyses (e.g., penetrometer) revealed higher soil compaction often associated with poorer rhizogenesis in BN trees (comparative root counts made in pits close to healthy or BN trees). Furthermore, initial BN symptoms were preferentially observed near the grafted bud at the rootstock/scion junction (RS/S). Numerous comparative ecophysiological measurements of leaf water potential, stem water potential, and predawn base potential using a plant moisture stress (PMS) pressure chamber indicated water stress in BN trees. These results and preliminary dye transfer studies at the RS/S junction suggested a nonoptimal vascular relation between the root system and the trunk of BN trees. In conclusion, compaction-associated reduced water availability of the soil and poor root capacity to meet the water demand during drier dry seasons combined with disturbed sap flows and recurrent local water drainage (latex flows) are now suspected to jointly act as the main exogenous causal stresses that induce the BN process at the RS/S bud zone before spreading upward to the tapping cut. This multidisciplinary approach gives a new comprehensive scenario for the emergence of this multifactorial physiological disease, now suspected to involve cyanide release (1) into the inner phloem of the rubber tree. References: (1) H. Chrestin. Plant Dis. 88:1047, 2004. (2) D. Nandris et al. Eur. J. For. Pathol. 21:325, 1991. (3) D. Nandris et al. Eur. J. For Pathol. 21:340, 1991. (4) F. Pellegrin et al. Plant Dis. 88:1046, 2004.