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The climatic conditions ofthe Mediterranean area results in vegetation and pollen very different from that ofthe other parts of Europe. The pollen content ofthe atmosphere of Montpellier, southern France, was examined using a filter sampler which was shown to be more efficient than most of the current devices for air sampling. Pollen counts were subsequently compared with pollinosis of patients born and living in and around Montpellier. The mean annual pollen counts showed that grass pollens and Cupressaceae pollens (cypress and juniper) are the highest. Some Mediterranean pollens (Oleaceae, London plane, Parietaria) are also important. Plantain and oak pollens are also present in relatively large amounts.Grass pollen allergy was found to be present in 86 5% of pollen-allergic patients. It was followed by plantain, Parietaria, Oleaceae, London plane and Cupressaceae pollens which were allergenic in 13-36% of pollen-allergic patients. Oak and pine pollens were present in large quantities in the counts but few persons were sensitive to oak and none to pine. By contrast, some patients had positive skin tests to alfalfa, red clover, acacia and lime tree pollens though these pollens were almost absent from the counts. In a few cases local sources of these pollens could account for the positive skin tests but cross-sensitivities could also occur. In summary, pollinosis of the Northern Mediterranean area is intermediate between the southern part ofthe area and the other parts of Europe.Correspondence: J. Bousquet, Clinique des Maladies Respiratoires,

Spheroplasts of the yeast Saccharomyces cerevisiae oxidize pyruvate at a high respiratory rate, whereas isolated mitochondria do not unless malate is added. We show that a cytosolic factor, pyruvate decarboxylase, is required for the non-malate-dependent oxidation of pyruvate by mitochondria. In pyruvate decarboxylasenegative mutants, the oxidation of pyruvate by permeabilized spheroplasts was abolished. In contrast, deletion of the gene (PDA1) encoding the E1␣ subunit of the pyruvate dehydrogenase did not affect the spheroplast respiratory rate on pyruvate but abolished the malatedependent respiration of isolated mitochondria. Mutants disrupted for the mitochondrial acetaldehyde dehydrogenase gene (ALD7) did not oxidize pyruvate unless malate was added. We therefore propose the existence of a mitochondrial pyruvate dehydrogenase bypass different from the cytosolic one, where pyruvate is decarboxylated to acetaldehyde in the cytosol by pyruvate decarboxylase and then oxidized by mitochondrial acetaldehyde dehydrogenase. This pathway can compensate PDA1 gene deletion for lactate or respiratory glucose growth. However, the codisruption of PDA1 and ALD7 genes prevented the growth on lactate, indicating that each of these pathways contributes to the oxidative metabolism of pyruvate.Pyruvate is a key intermediate in sugar metabolism. Three major pathways of pyruvate metabolism in the yeast Saccharomyces cerevisiae have been described (for a review, see Ref. 1) (Fig. 1). During fermentative growth, pyruvate is decarboxylated into acetaldehyde by pyruvate decarboxylase, which is, in its turn, reduced into ethanol in the cytosol by ADH1, one of the four known alcohol dehydrogenase isoenzymes (2, 3). This sequence of reactions allows the reoxidation of NADH, which is produced at the level of the glyceraldehyde-3-phosphate dehydrogenase. During respiratory metabolism, pyruvate can enter the mitochondria by a specific carrier (4, 5) and is decarboxylated and oxidized into acetyl-CoA by pyruvate dehydrogenase, a multienzyme complex located in the matrix (6). In addition, a pyruvate dehydrogenase bypass located in the cytosol converts pyruvate into acetyl-CoA by the action of the following enzymes: pyruvate decarboxylase (7), cytosolic acetaldehyde dehydrogenase (8, 9), and acetyl-CoA synthetases (10, 11). AcetylCoA synthesized in the cytosol is either directly used for the biosynthetic pathways or enters the mitochondria via the carnitine acetyltransferase system (12, 13). It has been proposed that this system works unidirectionally; i.e. acetyl-CoA can only move from the outside into inside (13). In contrast, direct oxidative decarboxylation of pyruvate into acetyl-CoA by the pyruvate dehydrogenase complex does not require ATP hydrolysis, since the energy required for the thioester formation is provided by oxidation of the carbonyl into carboxyl groups (Fig. 1). It is generally assumed that in wild-type S. cerevisiae grown under glucose limitation, the pyruvate dehydrogenase complex is primarily responsible for pyruvate c...