| Introduction:Circadian rhythm refers to an endogenous biological clock with a period of approximately 24 hours. In mammals, the circadian pacemaker is located in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. There is some evidence that circadian rhythms develop prenatally. At least twelve genes have been reported to be involved in regulating the circadian rhythm.Melatonin is the main hormone secreted by the pineal gland, which is connected to the SCN by multi-synaptic pathway. The synthesis and release of melatonin is promoted by darkness and is inhibited by light .The role of melatonin in the controlof circadian rhythm and human sleep has extensively been investigated by many authors. The significance of this hormone in the regulation of human circadian behavior is controversial, especially among those who have been exposed to phototherapy.Light-dark cycle change in the environment may be detected by the SCN through retino-hypothalamic tract (RHT) or through non-ocular photoreceptors. Light-dark cycle change can entrain the SCN to synchronize with the environment.Jaundiced neonates are usually treated with phototherapy and blue light is used as the main light source. Light reduces serum bilirubin level by converting poorly soluble indirect bilirubin into water-soluble photoisomers which can be excreted into bile and urine without liver conjugation. When neonates are exposed to the blue light during phototherapy, their eyes are covered to avoid retina damage. One of the most common clinical findings of behavior disorder in neonates during phototherapy is that they often present with an increased rate of crying and jitteriness. Whether this non-ocular light exposure could influence the expression of circadian rhythm in these neonates and how it is related to their vital sign or behavior change has not previously been investigated.Blood pressure monitoring is very important in the care of critically ill neonates. It is also an important parameter in evaluating the healthy of neonates. In our former study we measured systolic and diastolic blood pressure every 4 hours in the normal full-term during their first 48-hour-life and found there was circadian rhythm ofblood pressure in neonates, ie, the blood pressure reached its nadir at 2 o'clock, elevated to the highest from 6 to 10 o'clock, then declined at 14 o'clock, but elevated again at 18 o'clock, which was not as high as morning, then declined at 22 o'clock, to the lowest at 2 o'clock of the next day. Whether and how the blood pressure circadian pattern would change during phototherapy was another problem we concerned.In our present study, we examined the expression of Bmall and Cryl genes in the peripheral blood mononuclear cells (PBMC) and plasma melatonin levels of jaundiced neonates before and after phototherapy and tried to elucidate the influence of the commonly used phototherapy on the expression of circadian genes. We also measured the blood pressure every four hours in these neonates to examine a possible association with the regulation of circadian behavior during phototherapy.Part1 The Effect of Blue Light Exposure on the Expression ofOrcadian Genes: Bmall and cryptochromel in PeripheralBlood Mononuclear Cells in Jaundiced Neonates Objective:To evaluate the effects of blue light exposure on the expression of Bmall and cryptochromel in peripheral blood mononuclear cells and melatonin levels in plasma of jaundiced neonates. Subjects and methods:Subjects: Sixty-one jaundiced full term neonates, aged from 12 to 27 days, were recruited in the neonatal ward of Zhejiang Children's Hospital between September 2003 and May 2004. All infants were hospitalized for hyperbilirubinemia. Infants with birth asphyxia, prematurity, infection or hemolytic diseases were excluded from the study. Vital signs were monitored throughout the study. The infants were fed with breast milk before hospitalization and an infant formula after admission. Routine laboratory examinations were all normal except for high serum bilirubin level. Total serum bilirubin was 10-15...
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