How the sperm triggers the fertilisation calcium wave in the sea urchin egg

Fertilisation is characterised by an increase in cytosolic free calcium (Ca). This crucial event transforms the egg, releasing it from its state of cell cycle arrest and stimulating embryonic development. In the sea urchin egg the Ca1 increase is the result of increased polyphosphoinositide (PPI) hydrolysis and the production of the calcium mobilising internal messenger inositol 1,4,5-trisphosphate. I discuss the contribution of inositol polyphosphates to the calcium changes at fertilisation particularly their ability to stimulate calcium entry. I have used cortical granule exocytosis as an indicator of Ca1 and measured Ca1 in single eggs with the calcium sensitive fluorescent dye fura2. I show that, contrary to other reports, inositol phosphates activate eggs by a mechanism that is entirely independent of external calcium. A sperm activates an egg by triggering a regenerative response that involves calcium-stimulated PPI hydrolysis: in this way calcium release leads to further calcium release in an explosive manner. It has been suggested that the sperm triggers this response through a GTP-binding protein. However I show that an analogue of GDP, Guanosine-5'-O-(2-thiodiphosphate), that inhibits GTP-binding protein activation, does not prevent the sperm-induced increase in Ca or incorporation of the sperm into the egg. Also a GTP analogue, Guanosine-5'-O-thiotriphosphate, which stimulates GTP-binding proteins and causes egg activation, does so by a different mechanism than sperm. This data argues against the idea that a sperm triggers egg activation through a GTP-binding protein mechanism. The mobilisation of intracellular calcium through PPI hydrolysis and the production of inositol phosphates is a common signal transduction pathway present in many tissues. My data suggests that inositol phosphates act only to mobilise intracellular calcium and not to stimulate calcium influx. They also suggest that fertilisation in the sea urchin may involve a novel transduction pathway because the PPI hydrolysis is not linked to a GTP-binding protein as in other systems

Longitudinal cohort study investigating neurodevelopmental and socioemotional outcomes in school-entry aged children after open heart surgery in Australia and New Zealand: the NITRIC follow-up study protocol

Introduction: Despite growing awareness of neurodevelopmental impairments in children with congenital heart disease (CHD), there is a lack of large, longitudinal, population-based cohorts. Little is known about the contemporary neurodevelopmental profile and the emergence of specific impairments in children with CHD entering school. The performance of standardised screening tools to predict neurodevelopmental outcomes at school age in this high-risk population remains poorly understood. The NITric oxide during cardiopulmonary bypass to improve Recovery in Infants with Congenital heart defects (NITRIC) trial randomised 1371 children <2 years of age, investigating the effect of gaseous nitric oxide applied into the cardiopulmonary bypass oxygenator during heart surgery. The NITRIC follow-up study will follow this cohort annually until 5 years of age to assess outcomes related to cognition and socioemotional behaviour at school entry, identify risk factors for adverse outcomes and evaluate the performance of screening tools. Methods and analysis: Approximately 1150 children from the NITRIC trial across five sites in Australia and New Zealand will be eligible. Follow-up assessments will occur in two stages: (1) annual online screening of global neurodevelopment, socioemotional and executive functioning, health-related quality of life and parenting stress at ages 2–5 years; and (2) face-to-face assessment at age 5 years assessing intellectual ability, attention, memory and processing speed; fine motor skills; language and communication; and socioemotional outcomes. Cognitive and socioemotional outcomes and trajectories of neurodevelopment will be described and demographic, clinical, genetic and environmental predictors of these outcomes will be explored. Ethics and dissemination: Ethical approval has been obtained from the Children’s Health Queensland (HREC/20/QCHQ/70626) and New Zealand Health and Disability (21/NTA/83) Research Ethics Committees. The findings will inform the development of clinical decision tools and improve preventative and intervention strategies in children with CHD. Dissemination of the outcomes of the study is expected via publications in peer-reviewed journals, presentation at conferences, via social media, podcast presentations and medical education resources, and through CHD family partners.Trial registration numberThe trial was prospectively registered with the Australian New Zealand Clinical Trials Registry as ‘Gene Expression to Predict Long-Term Neurodevelopmental Outcome in Infants from the NITric oxide during cardiopulmonary bypass to improve Recovery in Infants with Congenital heart defects (NITRIC) Study – A Multicentre Prospective Trial’. Trial registration: ACTRN12621000904875

Longitudinal cohort study investigating neurodevelopmental and socioemotional outcomes in school-entry aged children after open heart surgery in Australia and New Zealand: the NITRIC follow-up study protocol

Introduction: Despite growing awareness of neurodevelopmental impairments in children with congenital heart disease (CHD), there is a lack of large, longitudinal, population-based cohorts. Little is known about the contemporary neurodevelopmental profile and the emergence of specific impairments in children with CHD entering school. The performance of standardised screening tools to predict neurodevelopmental outcomes at school age in this high-risk population remains poorly understood. The NITric oxide during cardiopulmonary bypass to improve Recovery in Infants with Congenital heart defects (NITRIC) trial randomised 1371 children Methods and analysis: Approximately 1150 children from the NITRIC trial across five sites in Australia and New Zealand will be eligible. Follow-up assessments will occur in two stages: (1) annual online screening of global neurodevelopment, socioemotional and executive functioning, health-related quality of life and parenting stress at ages 2-5 years; and (2) face-to-face assessment at age 5 years assessing intellectual ability, attention, memory and processing speed; fine motor skills; language and communication; and socioemotional outcomes. Cognitive and socioemotional outcomes and trajectories of neurodevelopment will be described and demographic, clinical, genetic and environmental predictors of these outcomes will be explored. Ethics and dissemination: Ethical approval has been obtained from the Children's Health Queensland (HREC/20/QCHQ/70626) and New Zealand Health and Disability (21/NTA/83) Research Ethics Committees. The findings will inform the development of clinical decision tools and improve preventative and intervention strategies in children with CHD. Dissemination of the outcomes of the study is expected via publications in peer-reviewed journals, presentation at conferences, via social media, podcast presentations and medical education resources, and through CHD family partners. Trial registration number: The trial was prospectively registered with the Australian New Zealand Clinical Trials Registry as € Gene Expression to Predict Long-Term Neurodevelopmental Outcome in Infants from the NITric oxide during cardiopulmonary bypass to improve Recovery in Infants with Congenital heart defects (NITRIC) Study - A Multicentre Prospective Trial'. Trial registration: ACTRN12621000904875.</p