261 Similarserum Transferrin Receptor in Preterm Compared with term Newborns: Fetal Erythropoiesis is Maintained in Preterms Despite Limited Iron Supply

Abstract

Objective: Pontosubicular neuron necrosis (PSN) represents an age-specific response to severe hypoxic-ischemic injury (HII) occurring in human neonates but not in older children or adults. Histologically, PSN is characterised by acute neuronal death in the pontine nuclei and the hippocampal subiculum bearing the hallmarks of apoptosis. The expression of Rbm3, a glycine-rich RNA-binding protein, is enhanced under hypoxic conditions and independent of HIF (hypoxia inducible factor). It is well known, that proteins which are dependant on HIF, e.g. Erythropoetin play an important role in HII. This study aims to determine whether the HIF-independent activation of Rbm3 is also a significant factor in the pathogenesis of PSN. Methods: We have investigated the expression of Rbm3 in human autopsy material consisting of 12 PSN cases and 10 age-matched controls without PSN. Immunohistochemistry and double labeling for Rbm3 and the astrocyte marker glial fibrillary acid protein (GFAP), the microglia/macrophage specific marker KiM1P and the neuronal marker NeuN was performed on formalin-fixed, paraffin-embedded brain specimens.Results: In PSN cases and controls, mainly neuronal cells expressed Rbm3. The number of immunopositive cells was significantly increased (pϭ0.001) in PSN cases. Predominantly degenerating cells with signs of later apoptotic stages showed Rbm3 expression. In earlier stages of apoptosis immunopositivity for Rbm3 was increased compared to contols, but less prominent.Conclusion: In addition to HIF-dependant proteins, the induction of the HIF-independent protein RMB3 is observed in response to human hypoxic-ischemic injury. 260 DEPARTMENT OF HOSPITAL PHYSICS, MRI UNIT AT THE KAROLINSKA UNIVERSITY HOSPITAL, STOCKHOLM, (SWEDEN)In magnetic resonance imaging (MRI) the trend is to move towards higher magnetic field strengths. This tendency is driven by the possibility to obtain better signal to noise ratios. One recent development is diffusion tensor imaging (DTI). As water diffusion is less hindered along the length of the axon than its cross section DTI allows for the investigation of the white matter microstructure. For example such histological correlates as the size cross sectional density, organization of axons and degree of myelination can be studied with this method. 13 preterm infants at term equivalent age and 6 healthy term newborn controls were studied. Median GA in the preterm group was 31 weeks, median postmenstrual age (PMA) ϭ 41 weeks when MR was performed. Term controls were examined at a median postnatal age of 2 days. Each subject underwent a single MRI examination on a 3 Tesla Trio Siemens scanner. MR protocol included a DTI sequence with 6 non-collinear diffusion weighting directions. From the raw data a diffusion tensor was estimated with linear least square fitting and from the tensor a scalar measure of anisotropic diffusion was calculated. This measure, called fractional anisotropy (FA), has been used to compare the groups. We present results demonstrating the feasibility of DTI at 3 Te...