Leaf Development in Lolium temulentum L.: Progressive Changes in Soluble Polypeptide Complement and Isoenzymes

Ougham, Helen J., Jones, Thomas W. A. and Evans, Mair LL. 1987.Leaf development in Lolium temulentum L.: progressive changesin soluble polypeptide complement and isoenzymes.—J. exp.Bot. 38: 1689–1696. The spectrum of soluble polypeptides extracted from segmentsof the developing 4th leaf of Lolium temulentum simplified withincreasing distance from the leaf base. Most of the metabolicallyimportant isoenzymes analysed also exhibited gradients of activitywith respect to distance from the base, and in some cases twoor more contrasting gradients were observed for a given enzyme. Key words: Gradients, isoenzymes, leaves, Lolium temulentum,, soluble polypeptides     

Expected future plague levels in a wildlife host under different scenarios of climate change

We predicted future plague and black-tailed prairie dog dynamics in the North American prairies under different scenarios of climate change. A climate-driven model for the joint dynamic of the host–parasite system was used. Projections for the regional climate were obtained through empirical–statistical downscaling of global climate scenarios generated by an ensemble of global climate models for the recent Fourth Assessment Report by the IPCC. The study shows the uncertainties involved in predicting future regional climate and climate-driven population dynamics, but reveals that unchanged or lower levels of plague, leading to increased black-tailed prairie dog colonies, can be expected. Less plague is particularly expected for scenarios that assume the highest emission of greenhouse gases associated with the greatest projected future warming. Moreover, under high-emission scenarios, decreased probabilities of extremely high numbers of infected colonies are expected, along with decreased probabilities of extremely low total numbers of colonies. The assumed main underlying mechanism is an inhibiting effect of high temperatures on fleas (dispersal vector) and on flea-mediated transmission of the disease-causing bacterium. Our study highlights the importance of using dynamic ecological (here host–parasite) models together with ensembles of climate projections to investigate the responses of populations and parasites to a changed climate.     

Effects of experimental warming on arctic willows (Salix spp.): a comparison of responses from the Canadian High Arctic, Alaskan Arctic, and Swedish Subarctic

Three species of dwarf, prostrate willow ( Salix arctica , S. rotundifolia and S. herbacea ) were subjected to experimental summer warming in high arctic Canada, arctic Alaska, and subarctic Sweden, respectively, as part of the International Tundra Experiment. Phenological and growth responses of these species were compared for the second season of the experiment. Stigmas became receptive and pollen dispersal occurred significantly earlier for S. rotundifolia and S. herbacea in the ITEX open-top chambers, but not for S. arctica . Warming had no effect on the timing of seed dispersal, leaf yellowing, or leaf senescence. The length and dry weight of the largest leaves were greater for warmed plants, and was significant for S. rotundifolia . The number of catkins/plot did not differ among species or treatments, but the fruit : flower ratio was reduced in the experimental plots.     

Structural determinants of the rate of protein folding

To understand the mechanism of protein folding and to assist rational design of fast-folding, non-aggregating and stable artificial enzymes, it is essential to determine the structural parameters which govern the rate constants of folding, kf. It has been found that -logkf is a linear function of the so-called chain topology parameter (CTP) within the range of 10(-1)s(-1)< or = kf < or =10(8)s(-1). The correlation between -logkf and CTP is much improved than using previously published contact order (CO) method. It has been further suggested that short sequence separations may be preferred for the establishment of stable interactions for the design of novel artificial enzymes and the modification of slow-folding proteins with aggregating intermediates.     

Validated method for the determination of risperidone and 9-hydroxyrisperidone in human plasma by liquid chromatography-tandem mass spectrometry

Since the first entry of risperidone on to the market in the early 1990s, investigation of the pharmacokinetic behaviour of the compound for which the availability of a bioanalytical method was a condition sine qua non, has received considerable attention. Most of the published methods, however, did not reach the level of sensitivity and selectivity which can be obtained today since the evolution of liquid chromatography-tandem mass spectrometry (LC-MS-MS) towards a routine technique in the bioanalytical laboratory. Therefore, we developed and validated a new LC-MS-MS method for the determination of risperidone and its active metabolite 9-hydroxyrisperidone in human plasma. This paper describes in detail the bioanalytical procedure and summarizes the validation results obtained. In addition, it focuses on the pitfalls one might encounter when developing similar assays. Despite the particular physicochemical characteristics of risperidone and 9-hydroxyrisperidone, the LC-MS-MS method enabled the quantification of both compounds down to 0.1 ng/ml. The method uses a sample preparation step by solid-phase extraction at pH 6 using a mixed-mode phase. In a short chromatographic run, separation of 9-hydroxyrisperidone from the minor metabolite 7-hydroxyrisperidone is achieved. Detection takes place by (turbo)ionspray tandem mass spectrometry in the positive ion mode. The validated concentration range is from 0.100 to 250 ng/ml, using 500 microliter of sample, with accuracy (bias) and precision (coefficient of variation) being below 15%. Although new developments in equipment will allow us to further improve and speed up the method, the assay reported can be used as a routine method to support a wide range of pharmacokinetic studies.