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In this short communication, we report on three striking phenomena of the circadian rhythm. One was observed with the non-linear concentration changes of the monomeric L-Cys and the non-linear yields of the L-Cys derived peptides, when undergoing spontaneous non-linear peptidization. The other one was observed with the binary L-Phe-L-Pro system, and the third one with L-Ser, D-Ser, and DL-Ser. So far, no analogous reports have been released on the circadian rhythm of the spontaneous non-linear peptidization of proteinogenic amino acids in a sterile abiotic environment (70% aqueous acetonitrile, or 70% aqueous methanol solutions). At the moment, we cannot find any rational explanation of this phenomenon, yet it seems highly probable that its origin is analogous to or even of a primordial nature for the circadian rhythm phenomena abundantly found in biological samples by other researchers. An experimentally established lack of the circadian rhythm with peptidization of the non-proteinogenic amino acid (D-Ser) can encourage us to revisit a still unsolved question of homochirality preconditions.

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Acta Physiologica Hungarica
Authors: R Bravo Santos, J Delgado, J Cubero, L Franco, S Ruiz-Moyano, M Mesa, AB Rodríguez, C Uguz, and C Barriga

, 1277 – 1285 ( 2013 ) 7. Bravo R , Cubero J , Franco L , Mesa M , Galán C , Rodríguez AB , Jarne C , Barriga C : Body weight gain in rats by a high-fat diet produces chronodisruption in activity/inactivity circadian rhythm

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Abstract  

Elemental concentration in each tissue of Japanese morning-glory (Pharbitis nil) during the growth was analyzed by INAA. Plants were grown in water culture for 4 days under 12-hour light and 12-hour dark condition. During the growth, 10 plants in the same developmental stage were periodically harvested. Then the plants were separated into 9 tissues to determine elemental concentration and water content. There was an elemental specific profile within the plant tissue, for example, Na and K concentrations were high in root whereas Mg and Ca concentrations were high at the upper part of the plants. Among the elements studied, Ca and Mg showed rhythmical change in concentration, increased during the day and decreased during the night. This tendency was especially noted at shoot apex. However, water content in all of the tissue was increased about 6 hours prior to the light period and showed maximum in the middle of the light period. About 6 hour difference of water content movement to those of Ca and Mg concentration suggested that water movement drives more dynamic change of each elemental concentration within a plant.

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Horne, J. A., Ostberg, O.: A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms. Int. J. Chronobiol., 1976, 4 (2), 97–110. 18

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The pond snail Lymnaea stagnalis acquires conditioned taste aversion (CTA) and maintains its memory for more than a month. Snails in our laboratory were cultured at 20 °C on a 12:12 light-dark cycle (light from 7 am to 7 pm). To examine the hours during which snails acquire CTA effectively, we trained some snails in the morning and others in the afternoon, and then compared their scores. CTA developed in both cases, but scores were significantly better in the morning than in the afternoon. To elucidate the cause of this difference in scores, we observed the voluntary activity of snails and found the circadian rhythm reflected in the snails' free-movement distances; distances at the circadian time 0-12 (daytime) were significantly longer than those at the circadian time 12-24 (nighttime). This rhythm was kept up for at least 3 days, even in constant darkness. In conclusion, L. stagnalis should be trained in the morning to acquire associative learning, possibly because of its greater propensity to roam about at that time as opposed to the afternoon.

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Melanin-concentrating hormone (MCH), the neuropeptide produced mainly in the hypothalamus, plays an operative role in regulating food intake and the sleep/wake cycle. Considering that these physiological functions pursue diurnal variations, we checked whether the total hypothalamic MCH level depends on the time of the day. The aggregated MCH peptide content of the whole MCH neuron population was significantly higher at the end of the sleeping period (lights on), than at the end of the active period (lights off). This result, together with earlier observations, indicates that in contrast to the MCH gene expression, the level of MCH peptide is object of circadian variation in the hypothalamus.

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. , Thomas , T. L. and Zoran , M. J. ( 2005 ): Circadian rhythms from multiple oscillators: lessons from diverse organisms . Nat. Rev. Genet. 6 , 544 – 556 . Benelli , G. ( 2014 ): Aggressive behavior and territoriality in the olive fruit fly

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. 2007 83 76 86 Shiga, S., Numata, H. (2009) Roles of PERIOD immunoreactive neurons in circadian rhythms and

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Hong CI, Zámborszky J, Baek M, Labiscsak L, Ju K, Lee H, Larrondo LF, Goity A, Chong HS, Belden WJ, Csikász-Nagy A: Circadian rhythms synchronize mitosis in Neurospora crassa . Proc Natl Acad Sci USA 111, 1397–1402 (2014

Open access
Acta Biologica Hungarica
Authors: Ágnes Gallé, Zalán Czékus, Krisztina Bela, Edit Horváth, Jolán Csiszár, and Péter Poór

Although the participation of glutathione transferases (GSTs) in light-dependent pathways and the circadian changes in the whole detoxification system have been studied, there are fewer results regarding the exact daily fluctuation of GSTs. In the present study, it was demonstrated that light up-regulated, while dark period decreased the plant GST activity and the expression of the selected tau group GST genes in tomato. These findings provide additional information on our current knowledge on the circadian rhythm of GSTs in plants and could help in further defining detoxification processes.

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