Enemy release does not increase performance of <Emphasis Type="Italic">Cirsium</Emphasis> <Emphasis Type="Italic">arvense</Emphasis> in New Zealand

Cirsium arvense (L.) Scop. (Californian, Canada, or creeping thistle) is an exotic perennial herb indigenous to Eurasia that successfully established in New Zealand (NZ) approximately 130 years ago. Presently, C. arvense is considered one of the worst invasive weeds in NZ arable and pastoral productions systems. A mechanism commonly invoked to explain the apparent increased vigour of introduced weeds is release from natural enemies. The enemy-release hypothesis (ERH) predicts that plants in an introduced range should experience reduced herbivory, particularly from specialists, and that release from this natural enemy pressure facilitates increased plant performance in the introduced range. In 2007, surveys were carried out in 13 populations in NZ (7 in the North Island and 6 in the South Island) and in 12 populations in central Europe to quantify and compare growth characteristics of C. arvense in its native versus introduced range. Altitude and mean annual precipitation for each population were used as covariates in an attempt to explain differences or similarities in plant traits among ranges. All plant traits varied significantly among populations within a range. Shoot dry weight was greater in the South Island compared to Europe, which is in line with the prediction of increased plant performance in the introduced range; however, this was explained by environmental conditions. Contrary to expectations, the North Island was not different from Europe for all plant traits measured, and after adjustment for covariates showed decreased shoot density and dry weight compared to the native range. Therefore, environmental factors appear to be more favourable for growth of C. arvense in both the North and South Islands. In accordance with the ERH, there was significantly greater endophagous herbivory in the capitula and stems of shoots in Europe compared to both NZ ranges. In NZ, capitulum attack from Rhinocyllus conicus was found only in the North Island, and no stem-mining attack was found anywhere in NZ. Thus, although C. arvense experiences significantly reduced natural enemy pressure in both the North and South Islands of NZ there is no evidence that it benefits from this enemy release.     

N-(Pyridin-2-yl) arylsulfonamide inhibitors of 11β-hydroxysteroid dehydrogenase type 1: Strategies to eliminate reactive metabolites

N-(Pyridin-2-yl) arylsulfonamides 1 and 2 (PF-915275) were identified as potent inhibitors of 11β-hydroxysteroid dehydrogenase type 1. A screen for bioactivation revealed that these compounds formed glutathione conjugates. This communication presents the results of a risk benefit analysis carried out to progress 2 (PF-915275) to a clinical study and the strategies used to eliminate reactive metabolites in this series of inhibitors. Based on the proposed mechanism of bioactivation and structure–activity relationships, design efforts led to N-(pyridin-2-yl) arylsulfonamides such as 18 and 20 that maintained potent 11β-hydroxysteroid dehydrogenase type 1 activity, showed exquisite pharmacokinetic profiles, and were negative in the reactive metabolite assay.

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Effects of Cortisol and Dexamethasone on Insulin Signalling Pathways in Skeletal Muscle of the Ovine Fetus during Late Gestation

Before birth, glucocorticoids retard growth, although the extent to which this is mediated by changes in insulin signalling pathways in the skeletal muscle of the fetus is unknown. The current study determined the effects of endogenous and synthetic glucocorticoid exposure on insulin signalling proteins in skeletal muscle of fetal sheep during late gestation. Experimental manipulation of fetal plasma glucocorticoid concentration was achieved by fetal cortisol infusion and maternal dexamethasone treatment. Cortisol infusion significantly increased muscle protein levels of Akt2 and phosphorylated Akt at Ser473, and decreased protein levels of phosphorylated forms of mTOR at Ser2448 and S6K at Thr389. Muscle GLUT4 protein expression was significantly higher in fetuses whose mothers were treated with dexamethasone compared to those treated with saline. There were no significant effects of glucocorticoid exposure on muscle protein abundance of IR-β, IGF-1R, PKCζ, Akt1, calpastatin or muscle glycogen content. The present study demonstrated that components of the insulin signalling pathway in skeletal muscle of the ovine fetus are influenced differentially by naturally occurring and synthetic glucocorticoids. These findings may provide a mechanism by which elevated concentrations of endogenous glucocorticoids retard fetal growth.     

Factors affecting 'Hass' avocado fruit size: Carbohydrate, abscisic acid and isoprenoid metabolism in normal and phenotypically small fruit

Carbohydrate and abscisic acid (ABA) metabolism were investigated in normal and phenotypically small 'Hass' avocado ( Persea americana Mill.) fruit in an attempt to link alterations in sugar and ABA content with changes in 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR, EC 1.1.1.34) activity and fruit size. The small-fruit phenotype was characterized by reduced seed HMGR activity, increased seed insoluble acid invertase ( β - d -fructofuranosidase, EC 3.2.1.26), decreased sucrose synthase (SS; UDP- d -glucose: d -fructose-2- α -glucosyl-transferase, EC 2.4.1.13) activity, decreased sucrose content, and increased glucose as a proportion of the total soluble sugar. Sucrose phosphate synthase (SPS; UDP- d -glucose: d -fructose 6-phosphate 2- α - d -glucosyltransferase, EC 2.4.1.14) activity was unaffected in seed but reduced in mesocarp of the small fruit. In addition, the small-fruit variant displayed enhanced respiration and both seed and mesocarp tissue showed increased ABA metabolism. Applied ABA caused an increase in insoluble acid invertase activity in seed tissue of normal fruit while mevastatin reduced HMGR activity in this tissue, caused sucrose depletion and increased the proportion of glucose from 5 to 57% of total soluble sugars. Exogenous glucose suppressed HMGR activity in seed tissue whereas in mesocarp tissue, HMGR activity was reduced to 38% of the control after 6 h but enhanced by 46% by 48 h. Glucose increased ABA biosynthesis and turnover in competent tissues. These results suggest that ABA turnover is mediated, in part, by carbohydrate content and composition which also affects HMGR activity. It is proposed that sugar and ABA signals act in concert to modulate expression and/or activity of HMGR in the control of 'Hass' avocado fruit growth and final fruit size.     

Blood pressure in a national birth cohort at the age of 36 related to social and familial factors,smoking, and body mass.

Blood pressure was measured in a birth cohort of 5362 subjects at the age of 36. The prevalence of hypertension in men (blood pressure greater than 140/90 mm Hg) was almost twice that in women, although women received treatment more often. Deaths of fathers of subjects from hypertensive and ischaemic heart disease were associated with significantly higher mean systolic and diastolic pressures in both sexes. Cigarette smoking was not strongly associated with blood pressure in men and not associated at all in women. Of the social factors, low social class of family of origin was associated with high blood pressure in both sexes; but the strongest association was with current body mass, and birth weight also contributed. Differences in blood pressures between the sexes may have been related to protective biological factors, such as endogenous sex hormones, in women and also to differences in types of employment, smoking habits, and body mass. Differences in blood pressures related to the social class of family of origin may reflect long term influences of class differences on diet, exercise, and educational achievement. The importance of measuring secular trends in obesity and blood pressures is emphasised.