The Development of Circadian Rhythms in Human Infants

2.1.1 Expression of interest contact on postnatal ward ................................... 60
2.1.2 Recruitment visits in the home .............................................................. 61
2.1.3 Home monitoring visits .......................................................................... 63
2.1.4 Further monitoring information required ............................................... 65
2.2 Infant temperature monitoring ...................................................................... 66
2.3 Collection of urine samples ........................................................................... 69
2.4 Estimation of creatinine ................................................................................ 70
2.5 Estimation of urinary melatonin .................................................................... 71
2.6 Estimation of urinary cortisol ........................................................................ 72
2.7 Use of Actiwatch for activity-rest measurement ........................................... 72
2.8 Gene expression measurement ...................................................................... 74
2.8.1 RNA preparation and cDNA synthesis .................................................. 75
2.8.2 Quantitative PCR (qPCR) ...................................................................... 75
2.9 Supplementary questionnaires ....................................................................... 78
2.10 Analysis ......................................................................................................... 78
2.11 Statistical methods ......................................................................................... 79
3 RESULTS .............................................................................................85
3.1 Recruited subjects and participant families .................................................. 85
3.1.1 Infant Recruitment ................................................................................. 85
3.1.2 Summary of demographic data .............................................................. 87
3.1.3 Socioeconomic demographics of participant families ........................... 91
3.2 Summary of Data Collected .......................................................................... 95
4 RESULTS .............................................................................................99
4.1 Core body temperature monitoring ............................................................... 99
4.2 Summary of development of core body temperature during night time sleep
…………………………………………………………………………….100
4.3 Changes in core body temperature with sleep relative to postnatal age ...... 102
4.3.1 Thermal Environment during night time sleep for infants ................... 112
5 RESULTS ...........................................................................................116
5.1 Analysis of urinary melatonin in infants ..................................................... 116
5.1.1 Changes to melatonin secretion relative to postnatal age .................... 118
5.1.2 Emergence of diurnal rhythm for melatonin secretion ........................ 121
5.1.3 Melatonin secretion relative to temperature maturation stage ............. 124
5.1.4 Relationship between night and day time log melatonin ..................... 128
6 RESULTS ...........................................................................................131
6.1 Analysis of urinary cortisol ......................................................................... 131
6.1.1 Changes to cortisol secretion relative to postnatal age ........................ 132
6.1.2 Emergence of diurnal rhythm for cortisol secretion ............................ 135
6.1.3 Cortisol secretion relative to temperature maturation stage ................ 138
6.1.4 Relationship between night and day time log cortisol ......................... 143
7 RESULTS ...........................................................................................146
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