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Query: UMLS:C0085593 (chills)
 4,268 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relation of membrane transport of alkali cations to their external concentrations or to their cellular contents was studied in HeLa cells. Chilling the cells at 0 degrees C reversed cell Na+ and K+ to a mirror image of the normal pattern. Upon rewarming to 37 degrees C the ouabain-sensitive Rb+ uptake became 2-fold faster than the control. A kinetic analysis revealed that the stimulation was due to an increase in the maximal rate of Rb+ uptake, Jmax. The increase in apparent Km was relatively small. The analysis also showed that the ouabain-sensitive cation transport system seemed to have two binding sites for Rb+. The stimulation of Rb+ uptake was related to an increase in cell Na+, and an addition of ouabain abolished such a relation. Net Na+ flux which was in the direction from inside the cells to the medium at hypernormal cell Na+ was iiincreased when cell Na+ ncreased. In contrast, net Na+ flux which was in the opposite direction in the presence of ovabain was reduced and became almost 0 at cell Na+ of 900 nmol/mg of protein. The Na+/Rb+ coupling ratio in the ouabain-sensitive cation transport was apparently less than 1 at nearly physiological cell Na+, but it approached 1.5 when cell Na+ was sufficiently high. The sum of cell K+ plus Rb+ varied inversely with cell Na+, and this relation was unaffected upon treatment with ouabain. When Rb+ uptake declined below 80% of the control, cell K+ plus Rb+ was reduced, however, 40% of the sum of cell cations was still preserved even after complete inhibition of the cation pumps by ouabain treatment of 2 hr. Interrelations of these results are discussed.
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PMID:Interrelation between membrane transport and the contents of alkali metal cations in HeLa cells. 628 2

Overnight exposure of cacao (Theobroma cacao L.) seedlings to chilling temperatures between 4.7 and 15.8 degrees C reduced net CO(2) assimilation rate (A) and stomatal conductance to water vapor (g(s)), with temperatures below 10 degrees C causing severe inhibition. Net CO(2) assimilation rates of chilled seedlings recovered to those of nonchilled plants within 7 days. No differences in daytime intercellular CO(2) concentration (c(i)) with overnight temperature were observed on the first day after the chilling treatment, which indicates that the reduction in photosynthesis was not caused by the reduction in stomatal conductance. However, c(i) of chilled plants was much less than that of nonchilled plants on the second day after treatment, which suggests that chilling caused a change in stomatal response to CO(2) concentration. Even 7 days after treatment, when A had recovered to control values, g(s) of chilled leaves was only approximately 70% that of controls. Chilling did not inhibit A through an effect on leaf water potential, which was higher in chilled plants than in unchilled plants.
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PMID:Net CO(2) assimilation of cacao seedlings following dark chilling. 1497 51