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Find video protocols related to scientific articles indexed in Pubmed.
Phase differences in expression of circadian clock genes in the central nucleus of the amygdala, dentate gyrus, and suprachiasmatic nucleus in the rat.
PLoS ONE
PUBLISHED: 01-01-2014
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We performed a high temporal resolution analysis of the transcript level of two core clock genes, Period2 (Per2) and Bmal1, and a clock output gene, Dbp, in the suprachiasmatic nucleus (SCN), the master circadian clock, and in two forebrain regions, the lateral part of the central nucleus of the amygdala (CEAl), and dentate gyrus (DG), in rats. These regions, as we have shown previously, exhibit opposite rhythms in expression of the core clock protein, PERIOD2 (PER2). We found that the expression of Per2, Bmal1 and Dbp follow a diurnal rhythm in all three regions but the phase and amplitude of the rhythms of each gene vary across regions, revealing important regional differences in temporal dynamics underlying local daily rhythm generation in the mammalian forebrain. These findings underscore the complex temporal organization of subordinate circadian oscillators in the forebrain and raise interesting questions about the functional connection of these oscillators with the master SCN clock.
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Rhythmic profiles of cell cycle and circadian clock gene transcripts in mice: a possible association between two periodic systems.
J. Exp. Biol.
PUBLISHED: 03-26-2013
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The circadian system shapes the rhythms of most biological functions. The regulation of the cell cycle by a circadian clock was suggested to operate via stages S, G2 and G2/M. This study investigated a possible time link at stages G1 and G1/S as well. The daily expression profiles of cell cycle markers (Ccnd1, Ccne1 and Pcna) and circadian clock genes (Per2 and Clock) were monitored in liver and esophagus (low and high proliferation index, respectively) of BALB/c mice. Locomotor activity displayed a 24 h rhythm, establishing the circadian organization of the suprachiasmatic nucleus. In the liver, the mRNA level of Per2 and Clock fitted the circadian rhythm with a 7.5 h shift. This temporal pattern suggests that the liver harbors a functional circadian clock. The rhythm of the analyzed cell cycle genes, however, was of low significance fitness and showed an opposite peak time between Pcna and Clock. These results indicate a weak regulatory role of the circadian clock. In the esophagus, the rhythms of Clock and Per2 mRNA had a similar peak time and non-circadian periods. These results suggest either that the esophagus does not harbor a functional circadian apparatus or that the phenotypes stem from differences in phase and amplitude of the rhythms of its various cell types. The similarity in the rhythm parameters of Clock, Ccne1 and Pcna transcripts questions the control of the circadian clock on the cell cycle along the G1 and G1/S stages. Yet the G1/S transition may play a role in modulating the local clock of proliferating tissues.
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Peripheral circadian clocks--a conserved phenotype?
Chronobiol. Int.
PUBLISHED: 02-20-2013
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The circadian system of mammals regulates the timing of occurrence of behavioral and physiological events, thereby optimizing adaptation to their surroundings. This system is composed of a single master pacemaker located in the suprachiasmatic nucleus (SCN) and a population of peripheral clocks. The SCN integrates time information from exogenous sources and, in turn, synchronizes the downstream peripheral clocks. It is assumed that under normal conditions, the circadian phenotype of different peripheral clocks would be conserved with respect to its period and robustness. To study this idea, we measured the daily wheel-running activity (WRA; a marker of the SCN output) in 84 male inbred LEW/Crl rats housed under a 12 h:12 h light-dark cycle. In addition, we assessed the mRNA expression of two clock genes, rPer2 and rBmal1, and one clock-controlled gene, rDbp, in four tissues that have the access to time cues other than those emanating from the SCN: olfactory bulbs (OBs), liver, tail skin, and white blood cells (WBCs). In contrast with the assumption stated above, we found that circadian clocks in peripheral tissues differ in the temporal pattern of the expression of circadian clock genes, in the robustness of the rhythms, and possibly in the number of functional ~24-h-clock cells. Based on the tissue diversity in the robustness of the clock output, the hepatic clock is likely to house the highest number of functional ~24-h-clock cells, and the OBs, the fewest number. Thus, the phenotype of the circadian clock in the periphery is tissue specific and may depend not only on the SCN but also on the sensitivity of the tissue to non-SCN-derived time cues. In the OBs and liver, the circadian clock phenotypes seem to be dominantly shaped by the SCN output. However, in the tail skin and WBC, other time cues participate in the phenotype design. Finally, our study suggests that the basic phenotype of the circadian clock is constructed at the transcript level of the core clock genes. Yet, additional posttranscriptional and translational events can contribute to the robustness and periodicity of the clock output.
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Comprehensive mapping of regional expression of the clock protein PERIOD2 in rat forebrain across the 24-h day.
PLoS ONE
PUBLISHED: 01-01-2013
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In mammals, a light-entrainable clock located in the suprachiasmatic nucleus (SCN) regulates circadian rhythms by synchronizing oscillators throughout the brain and body. Notably, the nature of the relation between the SCN clock and subordinate oscillators in the rest of the brain is not well defined. We performed a high temporal resolution analysis of the expression of the circadian clock protein PERIOD2 (PER2) in the rat forebrain to characterize the distribution, amplitude and phase of PER2 rhythms across different regions. Eighty-four LEW/Crl male rats were entrained to a 12-h: 12-h light/dark cycle, and subsequently perfused every 30 min across the 24-h day for a total of 48 time-points. PER2 expression was assessed with immunohistochemistry and analyzed using automated cell counts. We report the presence of PER2 expression in 20 forebrain areas important for a wide range of motivated and appetitive behaviors including the SCN, bed nucleus, and several regions of the amygdala, hippocampus, striatum, and cortex. Eighteen areas displayed significant PER2 rhythms, which peaked at different times of day. Our data demonstrate a previously uncharacterized regional distribution of rhythms of a clock protein expression in the brain that provides a sound basis for future studies of circadian clock function in animal models of disease.
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Endogenous dopamine regulates the rhythm of expression of the clock protein PER2 in the rat dorsal striatum via daily activation of D2 dopamine receptors.
J. Neurosci.
PUBLISHED: 10-22-2010
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A role for dopamine (DA) in the regulation of clock genes in the mammalian brain is suggested by evidence that manipulations of DA receptors can alter the expression of some clock genes outside the suprachiasmatic nucleus (SCN), the master circadian clock. The role of endogenous DA in the regulation of clock gene expression is unknown. Here, we demonstrate a direct relationship between extracellular DA levels and the rhythm of expression of the clock protein PERIOD2 (PER2) in the dorsal striatum of the male Wistar rat. Specifically, we show that the peak of the daily rhythm of extracellular DA in the dorsal striatum precedes the peak of PER2 by ?6 h and that depletion of striatal DA by 6-hydroxydopamine or ?-methyl-para-tyrosine or blockade of D(2) DA receptors by raclopride blunts the rhythm of striatal PER2. Furthermore, timed daily activation of D(2) DA receptors, but not D(1) DA receptors, restores and entrains the PER2 rhythm in the DA-depleted striatum. None of these manipulations had any effect on the PER2 rhythm in the SCN. Our findings are consistent with the idea that the rhythm of expression of PER2 in the dorsal striatum depends on daily dopaminergic activation of D(2) DA receptors. These observations may have implications for circadian abnormalities seen in Parkinsons disease.
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Cisplatin effects on rhythmic functions of mice: strain and tissue dependence.
Chronobiol. Int.
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The competence to preserve the optimal timing relationships between rhythmic variables enables adaptation of mammals to alternate environmental conditions. The capability to re-entrain depends on genetic factors and the nature of imposed time cues. In the present study, the authors examined in rodent models, following a cancer chronochemotherapy, cisplatin (CP), the rhythm patterns of locomotor activity and of a few biochemical variables (alkaline phosphatase and creatinine phosphokinase in kidney tissue and plasma, kidney urea nitrogen, and white blood cell count). Males of two inbred mice strains, BALB/c and c57Bl/6J, received 10 consecutive daily intraperitoneal (i.p.) injections of either saline or CP at zeitgeber time 22 (ZT22). CP administration altered the rhythms of each examined function in both strains. The type and extent of the changes varied among variables, tissues/plasma, and mouse strain. Yet, the effect of CP was not detected on all parameters, but only in ?60% of them. In addition, in the majority of the studied parameters, BALB/c and c57Bl/6J mice differed in their response to CP. The temporal parameters of period and peak time were more affected by CP than were the level ones of mesor (time series mean) and amplitude of variation. This observation may indicate the involvement of independent pathways of action upon each of the rhythm parameter sets. As a result, the rhythm phenotype of each function was modified and novel timing relationships were shaped. The results show that the circadian systems of BALB/c and c57Bl/6J mice failed to re-entrain after cessation of CP injections (tested on the first day following the 10 d course of CP administration), pointing to a direct effect of the medication on the tissues. The findings imply that optimal chemotherapeutic protocols should be tailored individually, according to the current temporal order rather than administered at a fixed predetermined circadian time. Further studies are necessary to determine which variables and rhythmic parameters could be useful to determine the optimal timing of chronochemotherapy.
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.