Kinetic characterization of human hydroxyacid–oxoacid transhydrogenase: Relevance toD-2-hydroxyglutaric and γ-hydroxybutyric acidurias

Summary We investigated the presence of hydroxyacid–oxoacid transhydrogenase (HOT), which catalyses the cofactor-independent conversion of γ-hydroxybutyrate (GHB) to succinic semialdehyde coupled to reduction of 2-ketoglutarate (2-KG) to D-2-hydroxyglutarate (D-2-HG), in human liver extracts employing [²H₆]GHB and 2-KG as substrates. We measured incorporation of ²H in D-[²H]2-HG using GC-MS analyses, providing evidence for HOT activity in humans. Kinetic characterization of HOT was undertaken in forward and reverse directions. We employed [²H₆]GHB and [²H₄]2-KG as cosubstrates in order to develop a HOT activity assay in cultured human fibroblasts derived from patients with D-2-hydroxyglutaric aciduria. HOT activity was quantified in this system by the measurement of D-[²H₅]2-HG production. Fibroblasts derived from patients with D-2-hydroxyglutaric aciduria showed normal HOT activities. Our results provide the first demonstration and preliminary kinetic characterization of HOT activity in human tissues.     

Lettuce necrotic leaf curl virus,a new plant virus infecting lettuce and a proposed member of the genus Torradovirus

A new virus was isolated from a lettuce plant grown in an open field in the Netherlands in 2011. This plant was showing conspicuous symptoms that consisted of necrosis and moderate leaf curling. The virus was mechanically transferred to indicator plants, and a total RNA extract of one of these indicator plants was used for next-generation sequencing. Analysis of the sequences that were obtained and further biological studies showed that the virus was related to, but clearly distinct from, viruses belonging to the genus Torradovirus. The name “lettuce necrotic leaf curl virus” (LNLCV) is proposed for this new torradovirus.     

B cell antigen receptor cross-linking induces tyrosine phosphorylation and membrane translocation of a multimeric Shc complex that is augmented by CD19 co-ligation

The SH2 domain-containing transforming Shc protein has been implicated in mitogenic signaling via several surface receptors through p21^ras. Following tyrosine phosphorylation by either receptor or non-receptor tyrosine kinases, Shc may interact with the adaptor protein Grb2, which is linked to Sos1, a guanine nucleotide exchange factor for human ras. Ligation of the antigen receptor complex on B cells (BCR) is known to activate various intracellular signaling pathways, which may accumulate in mitogenic responses. With respect to the initial steps, the activation of BCR-associated non-receptor tyrosine kinases appears to be indispensible. In this report we show that Shc proteins become tyrosine phosphorylated after BCR ligation on both transformed and normal human B cells. This is accompanied by the association of Shc with Grb2 proteins and a yet unidentified 145-kDa tyrosine phosphorylated protein. Subcellular fractionation revealed that this activation-induced multimeric Shc complex rapidly translocates towards the plasma membrane. Co-ligation of the BCR with the CD19 molecule results in a marked increase of these events, whereas CD19 cross-linking alone does not induce Shc tyrosine phosphorylation or translocation. Thus, in B cells the Shc complex may represent a molecular junction between the BCR and the mitogenic p21^ras cascade.     

Early numeracy in cerebral palsy: review and future research

Children with cerebral palsy (CP) often have problems with arithmetic, but the development of numerical abilities in these children has received only minor attention. In comparison, detailed accounts have been written on the arithmetic abilities of typically developing children, but a theoretical framework is still lacking. A promising perspective is the embodied cognition framework, which focuses on the influence of perception and action behaviours on cognition. We searched the literature to find the available studies on the early numeracy capacities of children with CP. We reviewed eight studies in which primary school-aged children with CP with a verbal IQ of at least 70 participated. The selected studies showed that these children are regularly delayed in performing simple arithmetic operations compared with their typically developing peers. However, owing to the limited number of studies no definite conclusions can be drawn regarding the precursors and developmental trajectories of arithmetic abilities in children with CP. We argue that the embodied cognition framework is well suited to scrutinize the arithmetic abilities of children with CP and provide future directions for research.