Diurnal variations in nicotinamide metabolism were found in these women. The biosynthesis of nicotinamide from tryptophan seemed to be increased by cold exposure.

We investigated whether exogenously supplied precursors of bergapten, namely umbelliferone, psoralen and bergaptol, could be utilized to produce bergapten without elicitation in Glehnia littoralis cell suspension cultures. The levels of added psoralen and bergaptol in the medium soon decreased, and this was followed by the detection of bergapten in both culture fluid and cells.Umbelliferone was also incorporated but in this case no bergapten was produced; instead, skimmin, umbelliferone monoglucoside, was detected. To determine whether conversion of psoralen to bergapten was due to enzyme induction by precursor feeding, the transcript accumulations and enzyme activities of bergaptol O-methyltransferase (BMT, EC 2.1.1.69), which catalyzes the last step of bergapten synthesis, and of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), which catalyzes the initial step of the phenylpropanoid biosynthetic pathway and is known as a marker enzyme of elicitation, were examined. The results showed that both the expression and the activity of BMT

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Differentiated shoot and root cultures of Glehnia littoralis were examined for organ-specific responses to yeast extract (YE). Growth, and changes in phenylalanine ammonia-lyase (PAL, EC 4. 1. 3. 5) activity, as well as furanocoumarin and simple phenylpropanoid production were then determined. YE affected root growth positively but negatively affected the growth of both the leaf and petiole. PAL activity was induced in all organs and reached a maximum after 2 days of treatment, though the activity in leaves was about three times higher than that in roots. A large amount of p-coumaric acid (p-CA) was transiently excreted into the culture medium of leaves, which has only been rarely reported to date. Subsequently, bergapten and xanthotoxin appeared in the medium. In contrast, no furanocoumarin was detected in the root cultures throughout the course of treatment. Changes in simple phenylpropanoid contents such as p-CA, caffeic acid (CafA) and ferulic acid (FA) in tissues were analyzed in three forms, i.e., free, soluble-conjugated and insoluble-conjugated forms. In leaves, little difference between control and YE-treated tissues was found except free p-CA, but every form of simple phenylpropanoid was increasingly elicited in the roots. These results indicate that YE acts bi-functionally on the root as a nutrient and an elicitor, but only as an elicitor in the leaf.

BackgroundProteins involved in the DNA damage response accumulate as microscopically-visible nuclear foci on the chromatin flanking DNA double-strand breaks (DSBs). As growth of ionizing radiation (IR)-induced foci amplifies the ATM-dependent DNA damage signal, the formation of discrete foci plays a crucial role in cell cycle checkpoint activation, especially in cells exposed to lower doses of IR. However, there is no quantitative parameter for the foci which considers both the number and their size. Therefore, we have developed a novel parameter for DNA damage signal based on the image analysis of the foci and quantified the amount of the signal sufficient for G2 arrest.ResultsThe parameter that we have developed here was designated as SOID. SOID is an abbreviation of Sum Of Integrated Density, which represents the sum of fluorescence of each focus within one nucleus. The SOID was calculated for individual nucleus as the sum of (area (total pixel numbers) of each focus) x (mean fluorescence intensity per pixel of each focus). Therefore, the SOID accounts for the number, size, and fluorescence density of IR-induced foci, and the parameter reflects the flux of DNA damage signal much more accurately than foci number. Using very low doses of X-rays, we performed a "two-way" comparison of SOID of Ser139-phosphorylated histone H2AX foci between G2-arrested cells and mitosis-progressing cells, and between mitosis-progressing cells in the presence or absence of ATM or Chk1/2 inhibitor, both of which abrogate IR-induced G2/M checkpoint. The analysis revealed that there was a threshold of DNA damage signal for G2 arrest, which was around 4000~5000 SOID. G2 cells with < 4000 SOID were neglected by G2/M checkpoint, and thus, the cells could progress to mitosis. Chromosome analysis revealed that the checkpoint-neglected and mitosis-progressing cells had approximately two chromatid breaks on average, indicating that 4000~5000 SOID was equivalent to a few DNA double strand breaks.ConclusionsWe developed a novel parameter for quantitative analysis of DNA damage signal, and we determined the threshold of DNA damage signal for IR-induced G2 arrest, which was represented by 4000~5000 SOID. The present study emphasizes that not only the foci number but also the size of the foci must be taken into consideration for the proper quantification of DNA damage signal.