The biology, pathogenesis and clinical aspects of acute lymphoblastic leukemia in children with Down syndrome.

Children with Down syndrome (DS) are at a 20-fold increased risk for acute lymphoblastic leukemia (DS-ALL). Although the etiology of this higher risk of developing leukemia remains largely unclear, the recent identification of CRLF2 (cytokine receptor like factor 2) and JAK2 mutations and study of the effect of trisomy of Hmgn1 and Dyrk1a (dual-specificity tyrosine phosphorylation-regulated kinase 1A) on B-cell development have shed significant new light on the disease process. Here we focus on the clinical features, biology and genetics of ALL in children with DS. We review the unique characteristics of DS-ALL on both the clinical and molecular levels and discuss the differences in treatments and outcomes in ALL in children with DS compared with those without DS. The identification of new biological insights is expected to pave the way for novel targeted therapies.

Rapid multiplication of adventitious somatic embryos in peach and nectarine by secondary embryogenesis.

Somatic embryos were multiplied by secondary embryogenesis in cotyledonary cultures of peach and nectarine (Prunus persica L.) using a simplified culture medium for immature seeds. A three-stage process with an initial callus phase was established in darkness on a medium containing basal salts (modified MS) supplemented with 2,4-D (5 mg/l), Kn (2 mg/l) and BAP (2 mg/l) and casein hydrolysate (500 mg/l). This was followed by a growth regulator-free medium with activated charcoal for the adventitious and direct multiplication of somatic embryos under continuous light. Somatic embryos (10-15) originated from the epidermal layer of primary somatic embryos of 4-6 mm size. The incidence of morphologically abnormal embryos was reduced by subculturing every 20 days. Calli which were isolated and grown on a 2,4-D medium were more embryogenic than those on NAA. These embryos multiplied continuously for more than 10 months by a repetitive somatic embryogenic process. A third stage medium, supplemented with BAP (2 mg/l), was required for axis elongation, germination and transfer to soil.