Pédiatrie 2008. [Pediatrics]

This year we present three papers on recent advances in paediatrics from the fields of neonatology, adolescent medicine and Duchenne muscular dystrophy. 1. Recent studies question the application of pure oxygen for neonatal reanimation and suggest that lower concentrations or even air may be more adequate for the reanimation of most newborns. 2. Bullying is an aggressive, repetitive and intentionally blessing behaviour. It is observed mainly at school and the victims are usually children with a weak personality or children suffering from chronic diseases. The doctor's role is to detect this behaviour and to help protect the victims. 3. The respiratory surveillance of patients with Duchenne muscular dystrophy is the corner-stone of their management. An algorithm allows to time correctly the initiation of non-invasive ventilation and to insure as long as possible a good life quality.

Impaired chemical coupling of cerebral blood flow is compatible with intact neurological outcome in neonates with perinatal risk factors.

Early detection of pathophysiological factors associated with permanent brain damage is a major issue in neonatal medicine. The aim of our study was to evaluate the significance of the CO2 reactivity of cerebral blood flow (CBF) in neonates with perinatal risk factors. Fourteen ventilated neonates with perinatal risk factors (pathological cardiotocogramm, low cord pH, postpartal encephalopathy) were enrolled into this prospective study. The study was performed 18-123 h after birth. CBF was measured using the noninvasive intravenous 133Xe method. Two measurements were taken with a minimal PaCO2-difference of 5 mm Hg. From the two CBF values the CO2 reactivity was calculated. Outcome was evaluated 1 year after birth. The CBF values at a lower PaCO2 ranged from 6.6 to 115. 2 ml/100 g brain issue/min (median = 18.2) and at a higher PaCO2 level from 7.1 to 125.7 ml/100 g brain tissue/min (median = 18.75). The calculated CO2 reactivity ranged from -9.6 to 6.6% (median 1.1%) change in CBF/mm Hg change in PaCO2. CO2 reactivity correlated with lowest pH (r2 = 0.35, p = 0.02). Two infants died, one of neonatal sepsis, the other of heart failure. Neurological outcome at the age of 1 year was normal in 11 patients, 1 had severe cerebral palsy. From the 12 surviving patients the patient with severe neurological deficit showed the highest CBF values (125.7 ml/100 g/min). Impaired chemical coupling of cerebral blood flow is compatible with intact neurological outcome in neonates with perinatal risk factors. CO2 reactivity in these newborns correlates with the lowest pH and may reflect the severity of perinatal asphyxia.

Mineralocorticoid receptor is essential for corticosteroid-induced up-regulation of L-type calcium currents in cultured neonatal cardiomyocytes.

Despite the fact that mineralocorticoid receptor (MR) antagonist drugs such as spironolactone and eplerenone reduce the mortality in heart failure patients, there is, thus far, no unambiguous demonstration of a functional role of MR in cardiac cells. The aim of this work was to investigate the activation pathway(s) mediating corticosteroid-induced up-regulation of cardiac calcium current (ICa). In this study, using neonatal cardiomyocytes from MR or glucocorticoid receptor (GR) knockout (KO) mice, we show that MR is essential for corticosteroid-induced up-regulation of ICa. This study provides the first direct and unequivocal evidence for MR function in the heart.

In vivo reprogramming of circuit connectivity in postmitotic neocortical neurons.

The molecular mechanisms that control how progenitors generate distinct subtypes of neurons, and how undifferentiated neurons acquire their specific identity during corticogenesis, are increasingly understood. However, whether postmitotic neurons can change their identity at late stages of differentiation remains unknown. To study this question, we developed an electrochemical in vivo gene delivery method to rapidly manipulate gene expression specifically in postmitotic neurons. Using this approach, we found that the molecular identity, morphology, physiology and functional input-output connectivity of layer 4 mouse spiny neurons could be specifically reprogrammed during the first postnatal week by ectopic expression of the layer 5B output neuron-specific transcription factor Fezf2. These findings reveal a high degree of plasticity in the identity of postmitotic neocortical neurons and provide a proof of principle for postnatal re-engineering of specific neural microcircuits in vivo.

Microtubule-associated protein 1a is involved in the early development of the rat spinal cord.

The expression of microtubule-associated protein 1a (MAP1a) in the developing rat spinal cord was studied using the monoclonal antibody BW6. Immunoblots of microtubule preparations revealed the presence of MAP1a in spinal cord tissue of rats aged embryonal day 16 and postnatal day 0. The spinal cord matrix layer, between embryonal days 12-17, displayed a pattern of MAP1a-positive processes, horizontally oriented in between the membrane limitans interna and externa. The mantle layer stained intensely for MAP1a between embryonal day 12 and postnatal day 2. MAP1a was found in neuronal cell bodies, axons and dendrites, located mainly in the ventral and intermediate mantle layer. In the marginal layer, MAP1a-positive axons could be observed between embryonal days 14-18. During further development, the intensity of the MAP1a staining in the spinal columns gradually decreased. These expression patterns indicate an involvement of MAP1a in the proliferation and differentiation of neuroblasts, and the maturation of the long spinal fiber systems, i.e. early events in spinal cord development

Congenital hydronephrosis: prenatal diagnosis and epidemiology in Europe.

OBJECTIVE: To describe prevalence, prenatal diagnosis and epidemiology of congenital hydronephrosis (CH) in Europe. MATERIAL AND METHOD: Data from a large European database for surveillance of congenital malformations (EUROCAT). The 20 participating registries are all based on multiple sources of information and include information about livebirths, fetal deaths with gestational age >or=20 weeks and terminations of pregnancy after prenatal diagnosis of malformations. Included were all cases with CH and born 1995-2004. RESULTS: There were 3648 cases with CH giving an overall prevalence of 11.5 cases per 10,000 births. The large majority of cases were livebirths (3506, 96% of total) and only 17 cases were fetal deaths and 120 were terminations of pregnancy. Almost all livebirths were alive 1 week after birth. Boys accounted for 72% of all cases. A high proportion of the cases (86%) had an isolated renal malformation. There were large regional differences in prevalence of CH ranging from 2 to 29 per 10,000 births. There was little regional variation in the prevalence of postnatally diagnosed cases while there were large regional differences in prevalence of prenatally diagnosed cases. CONCLUSION: Cases with CH are mainly livebirths, boys and survive the first week after birth. The large difference in prevalence seems to be related to the availability of prenatal screening in the region. The impact of over-diagnosis and potential over-treatment in regions with high prevalence or under-diagnosis with implications for renal function later in life in regions with low prevalence needs further investigation.

Transposition of great arteries and single coronary artery: a new surgical technique for the arterial switch operation.

A single coronary artery can complicate the surgical technique of arterial switch operations, impairing early and late outcomes. We propose a new surgical approach, successfully applied in a 2.1 kg neonate, aimed at reducing the risk of early and late compression and/or distortion of the newly constructed coronary artery system.

Reduction in the use of diagnostic tests in infants with risk factors for early-onset neonatal sepsis does not delay antibiotic treatment.

Despite a low positive predictive value, diagnostic tests such as complete blood count (CBC) and C-reactive protein (CRP) are commonly used to evaluate whether infants with risk factors for early-onset neonatal sepsis (EOS) should be treated with antibiotics. We investigated the impact of implementing a protocol aiming at reducing the number of diagnostic tests in infants with risk factors for EOS in order to compare the diagnostic performance of repeated clinical examination with CBC and CRP measurement. The primary outcome was the time between birth and the first dose of antibiotics in infants treated for suspected EOS. Among the 11,503 infants born at ≥35 weeks during the study period, 222 were treated with antibiotics for suspected EOS. The proportion of infants receiving antibiotics for suspected EOS was 2.1% and 1.7% before and after the change of protocol (p = 0.09). Reduction of diagnostic tests was associated with earlier antibiotic treatment in infants treated for suspected EOS (hazard ratio 1.58; 95% confidence interval [CI] 1.20-2.07; p <0.001), and in infants with neonatal infection (hazard ratio 2.20; 95% CI 1.19-4.06; p = 0.01). There was no difference in the duration of hospital stay nor in the proportion of infants requiring respiratory or cardiovascular support before and after the change of protocol. Reduction of diagnostic tests such as CBC and CRP does not delay initiation of antibiotic treatment in infants with suspected EOS. The importance of clinical examination in infants with risk factors for EOS should be emphasised.

3. Formation continue: promotion du mouvement et de l'activité physique chez les 0-6 ans

Sedentary lifestyle in children is increasing at an alarming rate. Now, promotion of physical activity by health professionals is a promising way. To support childhood specialists in this role, a transdisciplinary training is being developped.

Prognostic value of early MR imaging in term infants with severe perinatal asphyxia.

The prognostic significance of magnetic resonance imaging (MRI) in the neonatal period was studied prospectively in 43 term infants with perinatal asphyxia. MRI was performed between 1 and 14 days after birth with a high field system (2.35 Tesla). Neurodevelopmental outcome was assessed by a standardized neurological examination and the Griffiths developmental test at a mean age of 18.9 months. The predictive value of the various MRI patterns was as follows: Severe diffuse brain injury (pattern AII+III; n = 7) and lesions of thalamus and basal ganglia (pattern C; n = 5) were strongly associated with poor outcome and greatly reduced head growth. Mild diffuse brain injury (pattern AI; n = 7), parasagittal lesions (B; n = 7), periventricular hyperintensity (D; n = 2), focal brain necrosis and hemorrhage (E; n = 3) and periventricular hypointense stripes (on T2-weighted images; F; n = 3) led in one third of the infants to minor neurological disturbances and mild developmental delay. Infants with normal MRI findings (G; n = 9) developed normally with the exception of one infant who was mildly delayed at 18 months. The results indicate that MRI examination during the first two weeks of life is of prognostic significance in term infants suffering from perinatal asphyxia. Severe hypoxic-ischemic brain lesions were associated highly significantly with poor neuro-developmental outcome, whereas infants with inconspicuous MRI developed normally.

Temporal evolution of MR perfusion in neonatal hypoxic-ischemic encephalopathy

PURPOSE: To illustrate the evolution of brain perfusion-weighted magnetic resonance imaging (PWI-MRI) in severe neonatal hypoxic-ischemic (HI) encephalopathy, and its possible relation to further neurodevelopmental outcome. MATERIALS AND METHODS: Two term neonates with HI encephalopathy underwent an early and a late MRI, including PWI. They were followed until eight months of age. A total of three "normal controls" were also included. Perfusion maps were obtained, and relative cerebral blood flow (rCBF) and cerebral blood volume (rCBV) values were measured. RESULTS: Compared to normal neonates, a hyperperfusion (increased rCBF and rCBV) was present on early scans in the whole brain. On late scans, hyperperfusion persisted in cortical gray matter (normalization of rCBF and rCBV ratios in white matter and basal ganglia, but not in cortical gray matter). Diffusion-weighted imaging (DWI) was normalized, and extensive lesions became visible on T2-weighted images. Both patients displayed very abnormal outcome: Patient 2 with the more abnormal early and late hyperperfusion being the worst. CONCLUSION: PWI in HI encephalopathy did not have the same temporal evolution as DWI, and remained abnormal for more than one week after injury. This could be a marker of an ongoing mechanism underlying severe neonatal HI encephalopathy. Evolution of PWI might help to predict further neurodevelopmental outcome.

Inhibition of Notch Pathway Enhances Photoreceptor Commitment From Cultured Retinal Stem Cells

Purpose: Consequently to the principle that photoreceptors have to be at a very precise development stage to be successfully transplanted (MacLaren 2006), we are trying to mimic this development stage in vitro using retinal stem cells. The latter one isolated from the newborn mouse retina, derived from the radial glia population, which were previously isolated and characterized in our laboratory. We developed a protocol to commit these cells to the photoreceptor fate, but even if the percentage of cells expressing photoreceptor markers is high (30%), the differentiation process is incomplete so far (Merhi-Soussi 2006). Methods: In order to ameliorate photoreceptor differentiation, we hypothesized that the Notch pathway may interfere with this process by either promoting glia commitment, or maintaining an undifferentiated state. We are thus using a gamma-secretase inhibitor (DAPT), which inhibits Notch receptor cleavage and thus Notch activation. DAPT was used either during the whole differentiation stimulation, or only during a restricted period in two various retinal stem cell lines (RSC AA and RSC MP1). Results: RT-PCR performed during cell proliferation, showed the same positive expression in both cell lines for the following genes: Math3, Six3, Hes1, NeuroD, Pax6 and Notch1. Additionally, Mash1, Hes5, Prox1, Crx and Otx2 were detected in both cell lines but with a stronger expression in RSC MP1. Opposite results were obtained for Chx10. Nrl, Peripherin/RDS, GFAP and Math5 were detected neither in RSC AA, nor in RSC MP1. The constant presence of DAPT i) leads to a 233% (RSC AA) or 900% (RSC MP1) increase in peripherin/RDS-positive (photoreceptor marker) cells, compared to controls (no DAPT, n=3, P<0.02) along with a 68% (RSC AA) or 80% (RSC MP1) decrease in GFAP- positive cells (n=3, P<0.04), ii) modifies the ratio between uni-/bi- (23%) and multi- (77%) polar peripherin/RDS-positive cells to 45% and 55%, respectively, for both cell lines and iii) reduces by 50% the total cell number during the whole differentiation process for both cell lines. Conclusions: We are now exploring whether this reduction in total cell number is due to inhibition of cell proliferation or to cell death and whether photoreceptor differentiation is promoted instead of glial induction. We also want to confirm the results obtained with DAPT with RSCs isolated from Notch1-loxP mice. Such protocol may help to better mimic photoreceptor development, but this needs to be confirmed by genomic and proteomic profile analyses.

Bilateral transitory projection to visual areas from auditory cortex in kittens.

A transitory projection from primary and secondary auditory areas to the contralateral and ipsilateral areas 17 and 18 exists in newborn kittens. Distinct neuronal populations project to ipsilateral areas 17-18, contralateral areas 17-18 and contralateral auditory cortex; they are at different depth in layers II, III, and IV. By postnatal day 38 the auditory to visual projections have been lost, apparently by elimination of axons rather than by neuronal death. While it was previously reported that the elimination of transitory axons is responsible for focusing the origin of callosal connections to restricted portions of sensory areas it now appears that similar events play a more general role in the organization of cortico-cortical networks. Indeed, the elimination of juvenile projections is largely responsible for determining which areas will be connected in the adult.

Developmental changes in the heavy subunit of neurofilaments in the corpus callosum of the cat.

In the corpus callosum of the cat, the heavy subunit of neurofilaments (NFH) can be demonstrated with the monoclonal antibody NE14, as early as P11, not at P3, and only in a few axons. At P18-19 and more markedly at P29, many more callosal axons have become positive to NE14 and this is similar to what is found in the adult. In contrast, callosal axons become positive to the neurofilament antibody SMI-32 only between P29 and P39 and remain positive in the adult. Treatment with alkaline phosphatase prevents axonal staining with NE14, but results in SMI-32 staining of a few callosal axons as early as P11, but not at P3. Between P11 and P19 the number of axons stained with SMI-32 after alkaline phosphatase treatment increases, in parallel with that of axons stained with NE14. Thus NE14 appears to recognize a phosphorylated form of NFH, while SMI-32 appears to recognize an epitope of NFH which is either masked by phosphate or inaccessible until between P29 and P39, unless the tissue is treated with alkaline phosphatase. These two forms of NFH appear towards the end of the period of massive developmental elimination of callosal axons. They are also synchronous with changes in the spacing of neurofilaments quantified in a separate ultrastructural study. These cytoskeletal changes may terminate the juvenile-labile state of callosal axons and allow further axial growth of the axon.