In the yeast Saccharomyces cerevisiae there are two mating types, a and alpha, which may mate to produce an a/alpha diploid. Mating type is determined by the allele (MATa or MAT alpha) occupying the MAT locus. In a diploid, expression of the MATa1 and MAT alpha 2 genes determines the a/alpha state by regulating the expression of unlinked genes. Previous S1 endonuclease mapping implied that the MATa1 transcript is not processed. We have performed further S1 mapping of this transcript, demonstrating that the MATa1 gene contains two introns, unlike any other characterized nuclear gene in yeast. Both introns contain 5′ splice sites and 5′‐ TACTAACA ‐3′ consensus sequences at the positions predicted by the S1 mapping data. In the splicing‐defective rna2 mutant, the mature message disappears rapidly and the precursor RNA accumulates. The RNA processing removes the UGA stop codon which was previously believed to be read‐through.

1. The present review discusses the current evidence to implicate leucocytes as key players in the development of neointima in arteries that have been subjected to balloon angioplasty injury. 2. There is substantial clinical evidence that leucocytes are activated after angioplasty, as determined by increased plasma levels of both leucocyte granulation products and soluble leucocyte and endothelial cell adhesion molecules. 3. Experimental evidence to implicate leucocytes in neointimal formation comes from studies that demonstrate leucocyte accumulation occurs within the vascular wall soon after injury and that induction of leukopenia prevents neointimal formation. 4. The evidence implicating specific adhesion molecules and cytokines in the key events leading to neointimal formation is discussed.

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3-WEEK-OLD Hispanic boy was seen in the emergency department with a 2-day history of cough and rhinorrhea. This breast-fed in-fantwasthe3.1-kgproductofa36-weekges-tationtoa20-year-old,Spanish-speakingprimigravida woman. There had been exposure to a 16-yearold relative with an upper respiratory tract infection who was newly arrived from Mexico. In the emergency department the infant had a temperature of 38.2°C. Physical examination results were within normal limits and he was discharged. On the third day, the infant was seen in the clinic with cough and rhinorrhea. Examination revealed bilateral rhonchi, occasional substernal retractions with grunting, and a 2/6 systolic ejection murmur. The infant was admitted and a chest x-ray film was interpreted as being within normal limits (Figure 1, A). The white blood cell count (WBC) was 24.7 ϫ 10 9 /L with 0.42 neutrophils and 0.45 lymphocytes.Theinfantappearedtobedoingwellandwasdischarged for 2 days. The day after discharge (day 6 of illness), he was readmitted with lethargy, decreased oral intake, and dimin