PubMed · 5205852
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R A Luttring. 1971. Circadian rhythms.. https://pubmed.ncbi.nlm.nih.gov/5205852/
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Episodes of apnea during the first year of life have been classified with the term "Apparent Life-Threatening Events" (ALTE). Gastroesophageal reflux (GER) has been accepted to be one of the factors which can favor ALTE. The aim of this work is to study the continuous 24 h gastroesophageal pH-metering (fundamentally the Reflux Index [RI] and the Area Under Curve [AUC] parameters in three different periods of time: total pH-metering, pH-metering excluding the first two post-prandial hours, and pH-metering during sleep time, for 24 infants, 14 with ALTE and 10 without it). Between these two groups (with and without ALTE) there were no significant differences in the total pH-metering concerning the RI (2 +/- 1.2 vs 5.6 +/- 7.5 p > 0.05) and concerning the AUC (24.9 +/- 14.4 vs 67.4 +/- 84 p > 0.05), but in the analysis of the sleep period, the RI (p < 0.05) and the AUC (p < 0.01) both showed significant differences in the group of infants without ALTE. These results confirm that pH-metering study during sleep is the procedure of choice for recognizing infants with ALTE.
To allow continuous monitoring of the circadian clock in cyanobacteria, we previously created a reporter strain (AMC149) of Synechococcus sp. strain PCC 7942 in which the promoter of the psbAI gene was fused to Vibrio harveyi luciferase structural genes (luxAB) and integrated into the chromosome. Northern (RNA) hybridization and immunoblot analyses were performed to examine changes in abundance of the luxAB mRNA, the native psbAI mRNA, and the luciferase protein to determine whether bioluminescence is an accurate reporter of psbAI promoter activity in AMC149. Under constant light conditions, the mRNA abundances of both luxAB and psbAI oscillated with a period of approximately 24 h for at least 2 days. The expression of these two genes following the same pattern: both mRNAs peaked in the subjective morning, and their troughs occurred near the end of the subjective night. The amount of luciferase protein also oscillated with a period of approximately 24 h, and the protein rhythm is in phase with the bioluminescence rhythm. The rhythm of the luciferase mRNA phase-leads the rhythms of luciferase protein and in vivo bioluminescence by several hours. Comparable results were obtained with a short-period mutant of AMC149. Together, these results indicate that the bioluminescence rhythm in AMC149 is due primarily to circadian oscillation of psbAI promoter activity in this cyanobacterium.
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