[Hemolytic uremic syndrome in children of Mendoza, Argentina: association with Shiga toxin-producing Escherichia coli infection]. / Síndrome urémico hemolítico en niños de Mendoza, Argentina. Asociación con la infección por Escherichia coli productor de toxina Shiga.

Shiga toxin-producing Escherichia coli (STEC) has been associated with pathogenesis of hemolytic uremic syndrome (HUS) worldwide. The aim of the present study was to characterize the HUS cases reported in Mendoza and to determine their association with STEC infection. From July 1994 through June 1996 thirty-six patients with HUS were admitted to Hospital Pediátrico "Dr. HJ Notti" (Mean age 22.8 +/- 14.9 months, 44% females). The children developed HUS following an acute diarrheal illness in 94.4% of the cases. Bloody diarrhea was observed in 83.3% of them. Antimicrobial therapy had been administered to 69.4% of the patients. Most of the patients were well-nourished (88.9%), belong to middle-low socioeconomical condition (91.7%), from urban areas (72.2%) and they were mostly assisted during summer and the beginning of autumn. The acute stage of the disease occurred with presentation of pallor (100%), edema (25%), anuria (38.9%), oliguria (41.7%), hemolytic anemia (97.2%), thrombocytopenia (86.1%) and neurological involvement (41.7%). Twenty-five of them presented the full clinical syndrome. Peritoneal dialysis were performed in 50% and packed blood cell transfusion in 88.9%. The mean days of hospitalization was 15.1 +/- 9.2 [range 1-32]. A 91.7% of the patients recovered renal function, two developed chronic renal failure and one died. Cumulative evidence of STEC infection was found in 19 (86.4%) of 22 HUS patients. STEC O157:H7, biotype C was found in 8 (36.4%). The prevalent Stx type was Stx2 in STEC, free fecal Stx (STMF) and Stx-neutralizing antibodies (a-Stx). In Mendoza, as in the rest of Argentina E. coli O157:H7, biotype C, Stx2 producer is the most frequently detected pathogen in HUS cases.

The regulation of 1-aminocyclopropane-1-carboxylic acid synthase gene expression during the transition from system-1 to system-2 ethylene synthesis in tomato.

1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is one of the key regulatory enzymes involved in the synthesis of the hormone ethylene and is encoded by a multigene family containing at least eight members in tomato (Lycopersicon esculentum). Increased ethylene production accompanies ripening in tomato, and this coincides with a change in the regulation of ethylene synthesis from auto-inhibitory to autostimulatory. The signaling pathways that operate to bring about this transition from so-called system-1 to system-2 ethylene production are unknown, and we have begun to address these by investigating the regulation of ACS expression during ripening. Transcripts corresponding to four ACS genes, LEACS1A, LEACS2, LEACS4, and LEACS6, were detected in tomato fruit, and expression analysis using the ripening inhibitor (rin) mutant in combination with ethylene treatments and the Never-ripe (Nr) mutant has demonstrated that each is regulated in a unique way. A proposed model suggests that system-1 ethylene is regulated by the expression of LEACS1A and LEACS6. In fruit a transition period occurs in which the RIN gene plays a pivotal role leading to increased expression of LEACS1A and induction of LEACS4. System-2 ethylene synthesis is subsequently initiated and maintained by ethylene-dependent induction of LEACS2.