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Abstract  The aim of the present study was to assess the tolerance of Hevea brasiliensis to chilling temperatures since rubber production has been extended to sub-optimal environments. PB260 clone was used to analyze the responses of leaves chilled at 10°C during 96 h, as well as their recovery at 28°C. Some key parameters were used to evaluate photosynthetic apparatus functioning, membrane damage (electrolyte leakage) and oxidative stress. A short-term response versus a long-term one have been recorded, the time point of 24 h, when stomata closure was effective, being the border between the two responses. P n decreased dramatically at 1 h, and Fv/Fm was slightly affected. NPQ reached its maximal level between 4 and 7 h. Lipid peroxidation and membrane lysis were observed between 48 and 96 h. Activities of antioxidant enzymes increased, along with the induction of antioxidant gene expression. Finally, the plants were capable to recover (net photosynthetic rate, photochemical efficiency, antioxidant enzymes activities) when placed back to 28°C showing that PB260 can withstand long-term chilling. [ABSTRACT FROM AUTHOR]

The thyroid stimulating effect of tissue extracts was studied in rats. The serum levels of T, T and cAMP content of thyroid increased significantly at 2-4th hour and then returned to the initial values at 6th hour after injection of spleen extract. After injection of placenta extract, the same levels increased markedly as well. Their stimulating effects on the thyroid system were probably independent of the response of the adrenal system. Administration of morphine prior to injection of tissue extracts blocked their stimulating effects on serum levels of T, T and the cAMP content of thyroid. The above results demonstrate that tissue extracts of spleen and placenta are capable of stimulating hypothalamo-pituitary-thyroid axis possibly via hypothalamus. [ABSTRACT FROM AUTHOR]

A highly sensitive and precise method for the determination of the polyamines (including putrescine, spermidine and spermine) in cell culture media is described. The samples were concentrated by C18 column and the polyamines were converted to fluorometric derivatives with DNS-Cl. The polyamine derivatives were then completely separated by HPLC and determined by simultaneous fluorometric detection. The CV of intragroup and intergroup were 2.49% - 4.26% and 4.29% - 5.16%, respectively. The rate of recovery was 103% - 99%. There was trace amount of polyamines detected by this method in the media of F12. 8900, RPMI-1640, DMEM and M199 even without incubation with cells. So this method can be used for detecting the changes of polyamines in a medium before and after incubation with cells. It is helpful for the researches on the regulation of cell proliferation by polyamines. [ABSTRACT FROM AUTHOR]