Cytokinins of sycamore spring sap

Summary The cytokinins present in the spring sap of Acer pseudoplatanus L. were investigated. Ribosyl-trans-zeatin, trans-zeatin and dihydrozeatin were isolated and identified by combined gas chromatography-mass spectrometry (GC-MS). A number of other cytokinin active fractions were observed. One of these was less polar than zeatin and did not behave as any known cytokinin. Two other fractions were more polar than ribosylzeatin and were unstable. A decomposition product of one of these was identified as ribosyl-trans-zeatin by GC-MS. The possible nature of the unstable compounds is discussed. Data on the changes in cytokinin activity of the various fractions during spring 1973 are presented and discussed.Abbreviations GLC gas-liquid chromatography - GG-MS combined gas chromatography-mass spectrometry - KE kinetin equivalents - TLC thin-layer chromatography - TMS trimethylsilyl - tRNA transfer RNA - i⁶ Ade 6-(3-methylbut-2-enylamino)-purine - i⁶ Ado 6-(3-methylbut-2-enylamino)-9--D-ribofuranosyl-purine     

Optimising two-dye microarray designs for estimating associations with a quantitative trait

We discuss how the samples should be arranged in two-dye microarray studies when the objective is to investigate associations between gene expression and quantitative traits measured on each sample. Because there is typically large between array variation, information about the association will come from the differences in traits and expression measurements between the two values hybridised to the two dyes on the same array. It is shown that within-slide correlation of trait values should be minimised. The arrangement of samples for which this occurs will depend on the trait values in question, and is a computationally demanding problem. An alternative is to minimise the rank correlation. We discuss this and related issues for different combinations of numbers of samples and arrays. Data analysis, including estimation of the variance components, is also described.     

A high intake of industrial or ruminant trans fatty acids does not affect the plasma proteome in healthy men

Consumption of industrial trans fat raises the risk of cardiovascular disease, but it is unclear whether cis9,trans11-conjugated linoleic acid (CLA)--a trans fatty acid in dairy products--modulates disease development. We investigated the effects of complete diets providing 7% of energy as industrial trans fat or cis9, trans11 CLA, compared with oleic acid, on regulation of plasma proteins in 12 healthy men. Diets were provided for 3 wk each, in random order. Plasma was collected at the end of each 3 wk intervention period, depleted of its 12 most abundant proteins and analyzed by 2-DE. Principal component analysis of protein spot intensity values revealed that the nature of the dietary intervention did not significantly affect the plasma proteome. The intervention provided in the 1st period produced a significant treatment effect compared with the interventions provided in the other two periods, and there was a significant subject effect. In conclusion, the nature of an extreme dietary intervention, i.e. 7% of energy provided by industrial trans fat or cis9,trans11 CLA, did not markedly affect the plasma proteome. Thus plasma proteomics using 2-DE appears, by and large, an unsuitable approach to detect regulation of plasma proteins due to changes in the diet.     

Metabolomics of prolonged fasting in humans reveals new catabolic markers

Fasting is one of the simplest metabolic challenges that can be performed in humans. We here report for the first time a comprehensive analysis of the human ??fasting metabolome?? obtained from analysis of plasma and urine samples in a small cohort of healthy volunteers, using nuclear magnetic resonance (NMR), gas chromatography- and liquid chromatography-mass spectrometry (GC-MS and LC-MS). Intra- and inter-individual variation of metabolites was on measurement of four overnight fasting samples collected from each volunteer over a four week period. One additional sample per volunteer was collected following a prolonged fasting period of 36?h. Amongst a total of 377 quantified entities in plasma around 44% were shown to change significantly in concentration when volunteers extended fasting from 12 to 36?h. In addition to known markers (plasma free fatty acids, glycerol, ketone bodies) that reflect changes in the body??s fuel management under fasting conditions a wide range of ??new?? entities such as ??-aminobutyrate as well as other amino and keto acids were identified as fasting markers. Based on multiple correlations amongst the metabolites and selected hormones in plasma such as leptin or insulin-like-growth-factor-1 (IGF-1), a robust metabolic network with coherent regulation of a wide range of metabolites could be identified. The metabolomics approach described here demonstrates the plasticity of human metabolism and identifies new and robust markers of the fasting state.     

Planthopper‐rice interactions: unequal stresses on pure‐line and hybrid rice under similar experimental conditions

Hybrid and pure‐line (inbred) rice [Oryza sativa L. (Poaceae)] varieties have distinct physiologies, particularly as related to their nutrient requirements. These differences could confound the results and interpretation of experiments that compare rice varieties grown in pots for their resistance and responses to herbivores. In this study, a series of experiments was conducted to identify potentially confounding interactions between pot size (soil volume), fertilizer regime, and the use of acetate insect cages with rice line type (hybrid, fertile parental inbred, and male sterile inbred) during bioassays with the brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae). The growth of hybrid rice was often limited (relatively low biomass and low grain production) compared to fertile inbred lines even in large pots (7 200 ml) and when grown without added fertilizer. Several interactions between the effects of growth conditions and line type were detected. Acetate cages caused a significant reduction in grain yield in hybrids, but not in inbreds, mainly resulting from a cage‐induced decrease in grain weight (smaller grains). Hybrids and male sterile lines often had higher root or above‐ground biomass in the largest caged pots compared with fertile inbred lines, but biomass was similar in smaller pots, indicating that the large pots allowed longer unimpeded growth of fertile inbreds, but not other line types. There were no interactions between the presence or absence of planthoppers with line type or experimental conditions. All line types were equally susceptible to planthoppers. Often the effects of planthopper feeding on plant fitness (i.e., tolerance) were apparent when plants were grown in large pots but not in small pots, particularly for hybrid lines and under high nitrogen regimes. On the basis of these results we recommend that researchers ensure that plants are not unequally stressed by inadequate growth conditions during comparative studies with herbivores on physiologically distinct rice varieties or rice species. We recommend the use of large pots (soil volume) and lower fertilizer levels with young, non‐reproductive plants during comparative bioassays with planthoppers. Field cages are recommended for hybrid‐inbred comparisons during older plant stages but these are subject to a range of other confounding variables.     

DNA Methyltransferase Candidate Polymorphisms,Imprinting Methylation,and Birth Outcome

Background

Birth weight and prematurity are important obstetric outcomes linked to lifelong health. We studied a large birth cohort to look for evidence of epigenetic involvement in birth outcomes.

Methods

We investigated the association between birth weight, length, placental weight and duration of gestation and four candidate variants in 1,236 mothers and 1,073 newborns; DNMT1 (rs2162560), DNMT3A (rs734693), DNMT3B (rs2424913) and DNMT3L (rs7354779). We measured methylation of LINE1 and the imprinted genes, PEG3, SNRPN, and IGF2, in cord blood.

Results

The minor DNMT3L allele in the baby was associated with higher birth weight (+54 95% CI 10,99 g; p = 0.016), birth length (+0.23 95% CI 0.04,0.42 cm; p = 0.017), placental weight, (+18 95% CI 3,33 g; p = 0.017), and reduced risk of being in the lowest birth weight decile (p = 0.018) or requiring neonatal care (p = 0.039). The DNMT3B minor allele in the mother was associated with an increased risk of prematurity (p = 0.001). Placental size was related to PEG3 (p<0.001) and IGF2 (p<0.001) methylation. Birth weight was related to LINE1 and IGF2 methylation but only at p = 0.052. The risk of requiring neonatal treatment was related to LINE1 (p = 0.010) and SNRPN (p = 0.001) methylation. PEG3 methylation was influenced by baby DNMT3A genotype (p = 0.012) and LINE1 by baby 3B genotype (p = 0.044). Maternal DNMT3L genotype was related to IGF2 methylation in the cord blood but this effect was only seen in carriers of the minor frequency allele (p = 0.050).

Conclusions

The results here suggest that epigenetic processes are linked birth outcome and health in early life. Our emerging understanding of the role of epigenetics in health and biological function across the lifecourse suggests that these early epigenetic events could have longer term implications.