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991.
992.
Osmotic and ionic regulation in Nitella 总被引:2,自引:0,他引:2
When the osmotic value of an internodal cell of Nitella flexiliswas modified by the method of transcellular osmosis, the normalosmotic value was chiefly restored by the release or absorptionof K+. The release or uptake of Na+ was observed only when themodification of osmotic value was significant. Both the uptakeand release of K+ were linearly dependent on the degree of modificationof the osmotic value. The effectiveness of alkali metal cationsin restoring the osmotic value in cells of lower osmotic valueswas in the order K+>Rb+>Na+, Cs+>Li+. The absorptionof K+ by cells of lower osmotic values depended strongly ontemperature, while the release of K+ from cells of higher osmoticvalues did not. To clarify whether the Nitella cell regulates the osmotic valueor regulates the concentration of K+ in the vacuole, the cellsap was exchanged for artificial cell saps whose osmotic valuesand ionic concentrations were varied independent of each other.It was shown that in Nitella two regulating mechanisms are operating,one which regulates the osmotic value of the cell sap irrespectiveof the level of vacuolar K+ (0.1140 mM) and another whichregulates the vacuolar K+-level when it is abnormaly high (>160mM). Both mechanisms are assumed to operate in order to keepthe concentration of K+ in the cytoplasm at a constant level.The presence of Na+ (0100 mM) and Ca2+ (540 mM)did not affect the movement of K+ during osmoregulation.
1Present address: Sanki Engineering Limited, Nagaokakyo, Kyoto,Japan. (Received December 19, 1973; ) 相似文献
993.
ACTIVATION OF HEXOSE MONOPHOSPHATE PATHWAY IN BRAIN BY ELECTRICAL STIMULATION IN VITRO 总被引:2,自引:1,他引:1
Abstract— The incubation of cerebral cortical slices for 15 min in Krebs-Ringer-tris (pH 7.6) solution at 37°C with [1-14 C]glucose or [6-14 C]glucose as substrates yielded a C-1:C-6 14 CO2 ratio of 1.21, whereas this ratio increased to 3.01 after the application of electrical stimulation (ES). Tissue levels of 6-phosphoglu-conate (6PG) and glucose 6-phosphate (G6P), intermediary metabolites of hexose monophosphate (HMP) pathway, were 7 and 180 nmol/g tissue following 15 min incubation, and increased by 33 and 45 per cent respectively following the application of ES. Activities of 6-phosphogluconate dehydrogenase (6PGDH, 6-phospho- d -gluconate: NADP+ 2-oxidoreductase, EC 1.1.1.44) and glucose-6-phosphate dehydrogenase (G6PDH, d -glucose-6-phosphate: NADP+ 1-oxidoreductase, EC 1.1.1.49), important enzymes in regulating the activity of HMP pathway, in cerebral cortical slices were 689 and 907 pmol/mg protein/min and were increased by 66 and 25 per cent respectively by the application of ES. Synaptosomal G6PDH and 6PGDH activities were maximally activated by the addition of 40 m m -Na+ to the reaction mixture, whereas no activation by Na+ was observed in microsomal G6PDH and 6PGDH. Amobarbital inhibited more strongly the Embden–Meyerhof (EM) pathway than the HMP pathway, while imipramine had a stronger inhibitory effect on HMP pathway than on EM pathway in the electrically stimulated cerebral tissues.
The present results indicate that the HMP shunt pathway in the cerebral cortex is activated by the application of ES in vitro , possibly at synaptic regions and may play an important metabolic and functional role in the brain. 相似文献
The present results indicate that the HMP shunt pathway in the cerebral cortex is activated by the application of ES in vitro , possibly at synaptic regions and may play an important metabolic and functional role in the brain. 相似文献
994.
Shigeki Suzuki Hiroaki Hoshino Kazuma Yoshida Jun Nakanishi Shizu Tsuchiya-Hirata Seiji Kobuke Naoto Haruyama Fusanori Nishimura Hideki Shiba 《Biochemical and biophysical research communications》2018,495(3):2303-2309
Chromatin-enriched noncoding RNAs (ncRNAs) have emerged as key molecules in epigenetic processes by interacting with chromatin-associated proteins. Recently, protein-coding mRNA genes have been reported to be chromatin-tethered, similar with ncRNA. However, very little is known about whether chromatin-enriched mRNA is involved in the chromatin modification process. Here, we comprehensively examined chromatin-enriched RNA in squamous cell carcinoma (SQCC) cells by RNA subcellular localization analysis, which was a combination of RNA fractionation and RNA-seq. We identified 11 mRNAs as highly chromatin-enriched RNAs. Among these, we focused on the dentin matrix protein-1 (DMP-1) gene because its expression in SQCC cells has not been reported. Furthermore, we clarified that DMP-1 mRNA was retained in chromatin in its unspliced form in SQCC in vitro and in vivo. As the inhibition of the unspliced DMP-1 mRNA (unspDMP-1) expression resulted in decreased cellular proliferation in SQCC cells, we performed ChIP-qPCR to identify cell cycle-related genes whose expression was epigenetically modified by unspDMP-1, and found that the CDKN1B promoter became active in SQCC cells by inhibiting unspDMP-1 expression. This result was further validated by the increased CDKN1B gene expression in the cells treated with siRNA for unspDMP-1 and by restoration of the decreased cellular proliferation rate by simultaneously inhibiting CDKN1B expression in SQCC cells. Further, to examine whether unspDMP-1 was able to associate with the CDKN1B promoter region, SQCC cells stably expressing PP7-mCherry fusion protein were transiently transfected with the unspDMP-1 fused to 24 repeats of the PP7 RNA stem loop (unspDMP-1-24xPP7) and we found that unspDMP-1-24xPP7 was efficiently precipitated with the antibody against mCherry and was significantly enriched in the CDKN1B promoter region. Thus, unspDMP-1 is a novel chromatin-enriched RNA that epigenetically regulates cellular proliferation of SQCC. 相似文献
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998.
Life span and reproductive cost explain interspecific variation in the optimal onset of reproduction
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Emeline Mourocq Pierre Bize Sandra Bouwhuis Russell Bradley Anne Charmantier Carlos de la Cruz Szymon M. Drobniak Richard H. M. Espie Márton Herényi Hermann Hötker Oliver Krüger John Marzluff Anders P. Møller Shinichi Nakagawa Richard A. Phillips Andrew N. Radford Alexandre Roulin János Török Juliana Valencia Martijn van de Pol Ian G. Warkentin Isabel S. Winney Andrew G. Wood Michael Griesser 《Evolution; international journal of organic evolution》2016,70(2):296-313
Fitness can be profoundly influenced by the age at first reproduction (AFR), but to date the AFR–fitness relationship only has been investigated intraspecifically. Here, we investigated the relationship between AFR and average lifetime reproductive success (LRS) across 34 bird species. We assessed differences in the deviation of the Optimal AFR (i.e., the species‐specific AFR associated with the highest LRS) from the age at sexual maturity, considering potential effects of life history as well as social and ecological factors. Most individuals adopted the species‐specific Optimal AFR and both the mean and Optimal AFR of species correlated positively with life span. Interspecific deviations of the Optimal AFR were associated with indices reflecting a change in LRS or survival as a function of AFR: a delayed AFR was beneficial in species where early AFR was associated with a decrease in subsequent survival or reproductive output. Overall, our results suggest that a delayed onset of reproduction beyond maturity is an optimal strategy explained by a long life span and costs of early reproduction. By providing the first empirical confirmations of key predictions of life‐history theory across species, this study contributes to a better understanding of life‐history evolution. 相似文献
999.
Myc is one of the original reprogramming factors used to produce induced pluripotent stem cells. However, it is not necessary, instead its main role is to increase the efficiency of the reprogramming. The article by Scognamiglio et al ( 2016 ) helps clarify how. The authors show that Myc depletion leads to a reversible dormant state consistent with diapause. In this state, the cell sees its proliferation potential diminished but its pluripotency unchanged. The ability to coordinate the induction of this state should have important implications in cell differentiation. 相似文献
1000.
Hideaki E. Kato Keiichi Inoue Hideki Kandori Osamu Nureki 《BioEssays : news and reviews in molecular, cellular and developmental biology》2016,38(12):1274-1282