Daily oscillation and photoresponses of clock gene, Clock, and clock-associated gene, arylalkylamine N-acetyltransferase gene transcriptions in the rat pineal gland
ABSTRACT This study was conducted to investigate the circadian rhythms and light responses of Clock and arylalkylamine N-acetyltransferase (NAT) gene expressions in the rat pineal gland under the environmental conditions of a 12 h light (05:00-17:00 h): 12 h-dark (17:00-05:00 h) cycle (LD) and constant darkness (DD). The pineal gland of Sprague-Dawley rats housed under a LD regime (n=42) for four weeks and of a regime (n=42) for eight weeks were sampled at six different times, every 4 h (n=7 animals per time point), during a 24 h period. Total RNA was extracted from each sample, and the semiquantitative reverse transcription polymerase chain reaction (RT-PCR) was used to determine temporal changes in mRNA levels of Clock and NAT genes during different circadian or zeitgeber times. The data and parameters were analyzed by the cosine function software, Clock Lab software, and the amplitude F test was used to reveal the circadian rhythm. In the DD or LD condition, both the Clock and NAT mRNA levels in the pineal gland showed robust circadian oscillation (p<0.05) with the peak at the subjective night or at nighttime. In comparison with the DD regime, the amplitudes and mRNA levels at the peaks of Clock and NAT expressions in LD in the pineal gland were significantly reduced (p<0.05). In the DD or LD condition, the circadian expressions of NAT were similar in pattern to those of Clock in the pineal gland (p>0.05). These findings indicate that the transcriptions of Clock and NAT genes in the pineal gland not only show remarkably synchronous endogenous circadian rhythmic changes, but also respond to the ambient light signal in a reduced manner.
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ABSTRACT: The aim of this study was to investigate the reliability of the National Library of Medicine (NLM)'s Medical Subject Headings (MeSH) thesaurus for electronic indexing and retrieval of published chronobiologic papers. A sample set of 228 recent chronobiologic references was downloaded from the MEDLINE's database together with all MeSH entries associated with them. The following descriptors were analyzed among the headings of obvious chronobiologic relevance: chronobiology, chronobiology disorders, biological clocks, circadian rhythm, chronotherapy, drug administration schedule, periodicity, seasons, sleep disorders/circadian rhythm, and time factors. A comparison was made between the number of references identified by each heading and the number of articles actually pertinent to the same heading (as ascertained after reading each article of the sample set). This made possible an assessment of consistency (retrieved number not less than actual number) and accuracy (retrieved number not greater than actual number) of the usage of each MeSH entry. By reading each article, it was also possible to identify common chronobiologic concepts not yet associated with specific MeSH headings. In the preselected set of chronobiologic references, seasons identified all articles pertinent to seasonal variations and rhythms. However, chronobiology disorders missed 97.6% of its pertinent articles; periodicity, 95.2%; chronobiology, 87.7%; chronotherapy, 70%; time factors, 62.3%; and sleep disorders/circadian rhythm, 47.4%. Drug administration schedule missed 40% of the chronotherapeutic articles and identified 15% of the chronopharmacologic articles; biological clocks missed 24.1% of its pertinent articles and wrongly identified 8.3% of the retrieved articles; and circadian rhythm missed 2.7% of all circadian studies and wrongly identified 8.2% of the articles it retrieved. When used to search chronobiologic articles in the entire MEDLINE database, drug administration schedule, seasons, and time factors appeared to lack sufficient specificity to produce accurate results. Some common chronobiologic concepts were found not to be associated with any specific MeSH heading, namely, chronoepidemiology, chronopharmacology, chronotoxicology, chronotype, entrainment, and masking. For common chronobiologic concepts and definitions, the use of available MeSH headings appears to often yield inconsistent and inaccurate results; moreover, the MeSH thesaurus remains incomplete.Chronobiology International 02/2007; 24(6):1213-29. DOI:10.1080/07420520701791570 · 2.88 Impact Factor
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ABSTRACT: The main focus of this paper is a rigorous development and validation of a novel canonical correlation feature- selection (CCFS) algorithm that is particularly well suited for spectral sensors with overlapping and noisy bands. The proposed approach combines a generalized canonical correlation analysis framework and a minimum mean-square-error criterion for the selection of feature subspaces. The latter induces ranking of the best linear combinations of the noisy overlapping bands and, in doing so, guarantees a minimal generalized distance between the centers of classes and their respective reconstructions in the space spanned by sensor bands. To demonstrate the efficacy and the scope of the proposed approach, two different applications are considered. The first one is separability and classification analysis of rock species using laboratory spectral data and a quantum-dot infrared photodetector (QDIP) sensor. The second application deals with supervised classification and spectral unmixing, and abundance estimation of hyperspectral imagery obtained from the Airborne Hyperspectral Imager sensor. Since QDIP bands exhibit significant spectral overlap, the first study validates the new algorithm in this important application context. The results demonstrate that proper postprocessing can facilitate the emergence of QDIP-based sensors as a promising technology for midwave- and longwave-infrared remote sensing and spectral imaging. In particular, the proposed CCFS algorithm makes it possible to exploit the unique advantage offered by QDIPs with a dot-in-a-well configuration, comprising their bias-dependent spectral response, which is attributable to the quantum Stark effect. The main objective of the second study is to assert that the scope of the new CCFS approach also extends to more traditional spectral sensors.IEEE Transactions on Geoscience and Remote Sensing 11/2008; 46(10-46):3346 - 3358. DOI:10.1109/TGRS.2008.921637 · 2.93 Impact Factor
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ABSTRACT: Although studies involving the circadian response to time-zone transitions indicate that the circadian clock usually takes much longer to phase advance than delay, the discrepancy between the circadian resetting induced by photoperiod alteration via a dark or light period transition has yet to be investigated. In mammals, the pineal gland is an important component in the photoneuroendocrine axis, regulating biological rhythms. However, few studies have systematically examined the resetting process of pineal clock-gene expression to date. We investigated the resetting processes of four clock genes (Bmal1, Cry1, Per1, Dec1) and AANAT in the rat pineal gland after the light-dark (LD) reversal via a 24 h light or dark period transition. The resynchronization of the SCN-driven gene AANAT was nearly complete in three days in both situations, displaying similar resetting rates and processes after the differential LD reversals. The resetting processes of the clock genes were characterized by gene-specific, phase-shift modes and differential phase-shift rates between the two different LD reversal modes. The resetting processes of these clock genes were noticeably lengthened after the LD reversal via the light period transition in comparison to via the dark period transition. In addition, among the four examined clock genes, Per1 adjusted most rapidly after the differential LD reversals, while the rhythmic Cry1 expression adjusted most slowly.Chronobiology International 08/2009; 26(5):793-807. DOI:10.1080/07420520903044208 · 2.88 Impact Factor