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This thesis examines the role of vision in language development by focusing on: first, the understanding blind infants have of objects, actions/events and the way they start to talk about these aspects of their environment; and, second, the ways visual information contributes to conceptual and lexical development in sighted infants. Until recently, research has predominantly focused on infants' understanding of objects and their understanding of actions/events has been neglected. Since individuals who are blind predominantly have access to temporal, rather than spatial infomation and so are better able to process information about actions and events rather than objects, this bias seems to have led to the conclusion that an absence of visual information results in a cognitive deficit. Six blind/severely visually impaired infants and their sighted controls were studied for around a year using a range of quasi-experimental, parental report and observational techniques. The studies found little difference between the blind and sighted infants in the age of onset or rate at which first words are produced. However, blind infants were found to be delayed in the age at which they were able to comprehend and produce labels for objects and they produced few words for concrete, discrete objects. The finding that the blind infants were able to categorize objects/actions as well as generalise and extend their words calls into question Dunlea's (1989) claim that an absence of visual information leads to a cognitive deficit. It is argued that blind infants can make their way into language using a route which is merely one end of a spectrum of routes used by sighted infants. Implications are discussed for theories of lexical development (multiroute model, developmental lexical principles framework and the social-pragmatic framework) as well as for possible strategies facilitate conceptual and lexical development in blind/SVI and sighted infants.

Constraint induced movement therapy (CIMT) which is supported by motor learning theory has demonstrated promising results in improving upper limb function in hemiplegic cerebral palsy (HCP). However, its effectiveness within the NHS where children in the UK usually receive their therapy is little understood. To provide clarification, the author conducted a randomised controlled trial (n = 62) in 16 NHS paediatric community therapy services which compared the feasibility and effectiveness of a novel approach (prolonged restraint) of CIMT with usual NHS practice, in the young child with HCP. The primary outcome was bimanual performance measured with the Assisting Hand Assessment (AHA). Immediately post-intervention both groups changed and although there was not a statistically significant group difference the prolonged restraint methodology resulted in a larger effect (0.5 versus 0.2). The novel approach was safe, feasible, and acceptable to families and a more effective method of treatment delivery. The trial findings were combined in a systematic review and meta-analysis with a similar study and a treatment effect of 0.92 AHA logits was demonstrated. This is compatible with the smallest detectable difference (0.97 logits) indicating actual change in bimanual performance. The short-term efficacy, excellent recruitment and retention rates and acceptability of the trial procedures provides support for the trial feasibility and the need for a definitive investigation.

Biliary atresia is a common form of paediatric liver disease, with progressive, inflammatory obliteration of the biliary tree, leading to liver failure early in life. Mutations in PKHD1, encoding the ciliary protein fibrocystin, are associated with autosomal recessive polycystic kidney disease (ARPKD), a ciliopathy with clinical features that resemble biliary atresia. The hepatic developmental defects detectable in a significant number of infants with ARPKD are thought to be caused by dysfunction in the structure and function of primary cilia. The pathogenetic mechanism of both disorders is thought to be dysregulation of epithelial cell growth and tubulomorphogenesis. Preliminary investigations uncovered an association of PKHD1 sequence variants in a subset of biliary atresia patients with renal cysts, promoting further investigation to determine the functional role of fibrocystin in epithelial cells from renal and biliary tubules. Immunohistochemical studies, using a monoclonal antibody raised against wildtype fibrocystin, showed that it localises specifically to intrahepatic bile ducts. Absence of fibrocystin staining in end-stage liver tissue reflects ongoing damage to the intrahepatic biliary tree, rather than a phenomenon specific to biliary atresia. Studies utilising the Pkhd1 \(^{del2/del2}\) mouse model of ARPKD revealed 17β-estradiol sensitive centrosomal overduplication underlies the dysregulation of epithelial cell growth in renal tubules, however this does not appear to be in synergy with \(Pkhd1\) knockdown. Therefore, it remains uncertain whether sequence variants of PKHD1 are associated with biliary atresia.

Liver disease in children is rare but often serious, life long, and in many cases leads to death. Advances in diagnosing and treating liver disease (including liver transplant) have improved the outlook for children in many cases however little is known about the molecular pathogenesis of the disease, an understanding of which may identify specific therapeutic options. The aim of this thesis is to investigate the molecular genetics of rare liver disorders as the first step in advancing the understanding of liver disease pathogenesis. As a paediatric hepatologist I have identified cohorts of children in whom there is paucity of knowledge about the disease pathogenesis. I have studied three conditions in detail to encompass different clinical presentations. Chapter 3 summarises the investigation of the multisystem disorder, phenotypic diarrhoea of infancy (PDI), which causes cirrhosis or liver failure. Autozygosity mapping was used to identify the gene TTC37 in which mutations are associated with the PDI disease phenotype. Further work is now required to characterise TTC37, and use knockdown studies to identify whether TTC37 mutations are causative of the PDI phenotype. Chapter 4 describes the molecular genetic investigation of Jeune asphyxiating thoracic dystrophy (JATD), a chondrodysplasia with extra skeletal manifestations including hepatic ductal plate malformation and renal cyst development. Using autozygosity mapping, IFT80 was dentified in which mutations are associated with the JATD disease phenotype in 4% of ases. The diverse linical phenotype of JATD limits the utility of utozygosity mapping s it suggests there is genetic heterogeneity. The identification of IFT80 has led to JATD eing classified as a ciliopathy. Chapter 5 is the first description of eonatal liver failure to be associated with variants in ABCB11 which previously have only been associated with chronic liver disease and liver disease in pregnancy. This thesis has described the identification of the molecular genetic basis of rare causes of paediatric liver disease which has provoked many additional research questions. Future work will be to extend our knowledge of molecular genetics to all aspects of paediatric liver physiology so to classify disease according to the molecular pathogenesis such as a ciliopathy or bile salt transport defect.

Background: Docosahexaenoic acid (DHA), choline and uridine-5-monophosphate (UMP) are important brain nutrients which form phosphatidylcholine, the most abundant brain membrane phospholipid. DHA, choline and UMP supplementation increases rodent brain phospholipids, synaptic components, functional brain connectivity and cognitive performance. This novel pilot study supplemented infants at risk of neurological impairment (ARNI) with a nutrient combination containing these neurotrophic compounds. Aims: 1) In a double blind randomised control trial (RCT), investigate if intake of a specific nutrient combination improves neurodevelopmental and visual outcome in infants ARNI. 2) Using novel measures of cortical visual function, investigate the effect of perinatal brain injury severity, gestational age at birth and sex upon visuocognitive development in infants at risk of neurodevelopmental impairment. Method: Recruitment was from UK neonatal units. Eligibility: ≤ 31 weeks, weight < 9th percentile; < 31 weeks with ≥ Grade II intraventricular haemorrhage (IVH) or preterm white matter injury (PWMI); 31-40 weeks with ≥ Grade II IVH or PWMI, ≥ Sarnat Grade II HIE or defined brain MRI abnormalities. Stratification was by sex, gestation and brain injury severity. Randomised infants received neurotrophic supplementation or placebo, for 2 years. Primary outcome was Bayley Scales of Infant Development III (BSID III) composite cognitive score (CCS) after 2 years. Secondary outcomes included BSID III composite language score (CLS) and BSID III composite motor score (CMS). Cortical visual measures were pattern reversal visual event related potential (PR-VERP) latency (transient and calculated), orientation reversal visual event related potentials (OR-VERP), and the Fixation Shift test (FS). Functional behavioural vision was assessed using the Atkinson Battery of Child Development for Examining Functional Vision (ABCDEFV). Local Ethics Committee approval was granted. Results: 62 neonates were recruited. After 2 years, mean CCS in the intervention group was 87.7 (SD 20.4) and 81.6 (SD 18.5) in the placebo group (mean difference = 2.28, p=0.13; -0.2, 18.2). Mean CLS in the intervention group was 91.5 (SD 20.1) and 83.2 (SD 19.6) in the placebo group (mean difference = 2.74, p=0.1; -2.4, 18.3). CMS was similar in both groups. In relation to trial visual outcome measures, more infants in the placebo group gave a statistically significant OR-VERP response than in the intervention group (p=0.03). There were no statistically significant differences between the placebo and intervention on any other trial visual outcome measure. Cohort analyses indicate that transient PR-VERP latency is prolonged in children at risk of neurodevelopmental disability compared to typically developing infants (mean difference = -23.3, p=0.015, 95% CI -42.10 - -4.54). Calculated PR-VERP latency is prolonged to an even greater extent in children at risk of neurodevelopmental disability compared to typically developing infants (mean difference -148.6, p=0.000, 95% CI -179.7- -117.43), and remains prolonged across the age range tested. Conclusions: 1) The difference in CCS and CLS between intervention and placebo groups represents a clinically significant effect size. Use of neurotrophic micronutrient supplementation in infants ARNI warrants exploration in a large multicentre RCT. 2) Calculated PR-VERP latency may be a more appropriate outcome measure of cortical visual function than transient PR-VERP latency in infants at risk of neurodevelopmental disability.

A wider understanding of the impact of each of the dietary components on blood phenylalanine concentrations in PKU may lead to improvements in management. Knowledge of the effects of such rigorous diet therapy on feeding behaviour is also important. In a series of studies, the effect of a number of dietary factors on plasma phenylalanine control and of diet on feeding behaviour was systematically investigated. The key findings were: 1) there is wide variability in plasma phenylalanine concentrations which were not reflected in a single early morning phenylalanine measurement; 2) plasma phenylalanine concentrations were more influenced by the timing and dosage of protein substitute than by total energy or excess natural protein intake from ‘freely’ allowed foods; 3) repeated 4 hourly administration of protein substitute throughout 24-hours markedly reduced phenylalanine variability and led to lower phenylalanine concentrations; 4) ‘free’ use of fruits and vegetables containing phenylalanine between 51-100 mg/100g did not adversely affect plasma phenylalanine control; and 5) feeding problems were common, with almost 50% of young children with PKU exhibiting at least 3 feeding problems. These findings in PKU are important in the understanding of feeding behaviour; the interpretation of plasma phenylalanine concentrations; they increase and rationalise the range of ‘free’ foods; and will reduce 24-hour plasma phenylalanine variability, and thus, possibly increase dietary phenylalanine tolerance.

Introduction: Despite the importance of pharmacokinetic (PK) information for patient management there are low numbers of paediatric PK studies and little guidance available on optimum study design and conduct. Method: Drawing on Implementation Science, a mixed-methods study was conducted, including a scoping review (SR) (PK literature: 1990-2015) and quantitative and qualitative inquiry (stakeholders: lay population, service users and health-care professionals). Aim: to explore the feasibility and acceptability of paediatric PK research. Results: The SR (203 papers) highlighted significant problems with participant recruitment, retention and sampling. Stakeholders (n=240) added insight into these phenomenon, with lack of research staff, additional blood-sampling and appointments highlighted as significant barriers to recruitment and conduct. Facilitators included sensitivity and timeliness of approach, communication, involvement of child/young person (CYP) in decision-making, engagement between research and clinical teams, reassurance of safety, pain minimisation, and avoidance/reduction of burden to the CYP and family. Dedicated research support was viewed as critical to success. Discussion: PK research was viewed as feasible and acceptable by service users and health professionals, even in the context of critical illness. Novel, evidence-based, patient-centred, recommendations for future PK study conduct and design have been generated which are applicable for those designing, approving and implementing PK research.

The traditional roles of the tumor suppressor protein, p53, in transcriptional regulation are mostly defined in cancer or stressed cells and are centered on control of the cell cycle, DNA repair or senescence. In this thesis, data is presented demonstrating that the p53-regulated transcriptome is highly context-dependent as illustrated using the developing kidney as a model system. To this end, we utilized whole genome transcriptome and ChIP-Seq (chromatin immunoprecipitation-high throughput sequencing) analyses in p53+/+ and p53-/- mice to identify p53 regulated pathways in the embryonic kidney. This integrated approach allowed identification of novel genes that are direct p53 targets in the developing nephron. This approach was further refined using RNA-Seq analysis of lineage-tagged FACS-isolated nephron progenitors. We find that the p53-regulated transcriptome in the embryonic kidney is mostly involved in development, morphogenesis, and metabolic pathways. Interestingly, traditional targets of p53, such as DNA repair, cell cycle and apoptosis, accounted for < 5% of differentially expressed genes. The majority of 7,893 p53-binding genomic regions contain consensus p53 binding sites. Unlike a cancer cell line in which 7% of p53 binding sites lie within proximal promoters, 78% of p53 peaks in the developing kidney overlies the promoter. Moreover, 25% of the differentially expressed p53-bound genes belong to nephron progenitors and nascent nephrons, including key transcriptional regulators, components of Fgf, Wnt, Bmp, and Notch pathways, and ciliogenesis genes. RNA-Seq of nephron progenitors from wild-type and mutant p53 mice demonstrated repression of the nephron stem cell marker, Cited1, but not Six2. Moreover, cytoskeleton, cell adhesion, and energy metabolism genes were downregulated in mutant progenitors consistent with the loosely organized cap mesenchyme and disrupted mesenchyme-to-epithelium transition of p53-/- progenitors. In conclusion, our studies demonstrate that p53 genomic occupancy and regulated transcriptome are distinctly different in development and cancer. p53 is a key regulator of transcriptional programs that maintain nephron niche integrity, nephron progenitor cell renewal and differentiation. / acase@tulane.edu

The degree to which the normal eye can adapt to the dark is related to or dependent upon the eye's ability to regenerate visual purple. The relationship of vitamin A to the visual cycle has caused much development in improved methods of detecting vitamin A deficiency. For the most part these methods have been applied to adults and school age children. This study seeks to analyze this method as applied to pre-school age children.