Plasma atriopeptin response to prolonged cycling in humans.

The exercise-induced increase in plasma atriopeptin (ANP) has been related to exercise intensity. The independent effect of duration on the ANP response to dynamic exercise remains incompletely documented. The purpose of this study was to describe the time course of plasma ANP concentration during a 90-min cycling exercise protocol and to examine this in light of concurrent variations in plasma arginine vasopressin (AVP), aldosterone (ALD), and catecholamine (norepinephrine and epinephrine) concentrations as well as plasma renin activity (PRA). Seven male and four female healthy college students (23 +/- 2 yr) completed a prolonged exercise protocol on a cycle ergometer at an intensity of 67% of maximal O2 uptake. Venous blood was sampled through an indwelling catheter at rest, after 15, 30, 45, 60, and 90 min of exercise, and after 30 min of passive upright recovery. Results (means +/- SE) indicate an increase in ANP from rest (22 +/- 2.6 pg/ml) at 15 min of exercise (45.3 +/- 7.4 pg/ml) with a further increase at 30 min (59.4 +/- 9.8 pg/ml) and a leveling-off thereafter until completion of the exercise protocol (51.7 +/- 10.7 pg/ml). In plasma ALD and PRA, a significant increase was found from rest (ALD, 21.4 +/- 6.4 ng/dl), PRA, 2.5 +/- 0.5 ng.ml-1.h-1 after 30 min of cycling, which continued to increase until completion of the exercise (ALD 46.6 +/- 8.7 ng/dl, PRA 9.5 +/- 0.9 ng.ml-1.h-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Most networks in Wagner's model are cycling

In this paper we study a model of gene networks introduced by Andreas Wagner in the 1990s that has been used extensively to study the evolution of mutational robustness. We investigate a range of model features and parameters and evaluate the extent to which they influence the probability that a random gene network will produce a fixed point steady state expression pattern. There are many different types of models used in the literature, (discrete/continuous, sparse/dense, small/large network) and we attempt to put some order into this diversity, motivated by the fact that many properties are qualitatively the same in all the models. Our main result is that random networks in all models give rise to cyclic behavior more often than fixed points. And although periodic orbits seem to dominate network dynamics, they are usually considered unstable and not allowed to survive in previous evolutionary studies. Defining stability as the probability of fixed points, we show that the stability distribution of these networks is highly robust to changes in its parameters. We also find sparser networks to be more stable, which may help to explain why they seem to be favored by evolution. We have unified several disconnected previous studies of this class of models under the framework of stability, in a way that had not been systematically explored before.     

Intramyocellular triacylglycerol in prolonged cycling with high- and low-carbohydrate availability.

Vastus lateralis intramyocellular lipid (IMCL) content was assessed by (1)H-magnetic resonance spectroscopy before and after prolonged time trial cycling bouts of approximately 3-h duration. Six highly trained male cyclists completed a double-blind, randomized, crossover design of two experimental trials after a strenuous exercise bout and 48 h of high (HC) (9.32 +/- 0.08 g. kg(-1). day(-1)) and low (LC) (0.59 +/- 0.21 g. kg(-1). day(-1)) dietary carbohydrate. Resting IMCL content was significantly higher after LC vs. HC (P < 0.01) and was reduced during exercise by 64 and 57%, respectively. IMCL was not different between conditions after exercise (P > 0.05). The approximately twofold increase in IMCL degradation in LC compared with HC suggests that higher rates of whole body lipid metabolism in LC were in part attributable to a greater IMCL utilization. Four subjects experienced reductions of IMCL in excess of 70% during exercise. To our knowledge, this is the first study to report near depletion of IMCL during prolonged cycling, indicating that IMCL, presumably the triacylglycerol component, may be exhausted by prolonged strenuous exercise.     

Effect of glucose polymer diet supplement on responses to prolonged successive swimming, cycling and running

Fifteen male endurance athletes were studied to determine the effect of a glucose polymer (GP) diet supplement on physiological and perceptual responses to successive swimming, cycling and running exercise. Thirty min of swimming, cycling and running at 70% VO2max, followed by a run to exhaustion at 90% VO2max was performed after one week of training under two dietary conditions: 1) GP (230 g of GP consumed daily) and 2) placebo (P, saccharin-sweetened supplement consumed daily). During GP, daily carbohydrate (CHO) intake was higher (p less than 0.05) by 173 g or 14% of energy intake than during P, but total energy intake was not significantly different. During 90 min of exercise, CHO utilization and blood glucose were significantly higher under GP than P by an average of 20.2% and 14.5%, respectively, but heart rate, ventilation, oxygen uptake, ratings of perceived exertion, and plasma lactate were not different. Run time to exhaustion at 90% VO2max was significantly longer by 1.2 min (23%) under GP. The results suggest that a GP diet supplement may be of value during endurance exercise by increasing the availability of CHO.     

Microbial interventions are an easier alternative to engineer higher organisms

Advances in synthetic biology have made microbes easier to engineer than ever before. However, synthetic biology in animals and plants has lagged behind. Since it is now known that the phenotype of higher organisms depends largely on their microbiota, we propose that this is an easier route to achieving synthetic biology applications in these organisms.

A transition from reading to writing biology has blurred the lines between basic science and engineering creating the field of synthetic biology. With an ever‐expanding genetic toolbox, we now manipulate natural biological systems to optimize our anthropocentric activities. From the synthesis of complex aromatic compounds, to the production of safer vaccines, a problem identified may find its solution lying in the metabolism of a single cell. Initially, synthetic biology was largely focused on the production of such commodities at the industrial scale, not only to maximize profitability, but also to minimize energy and resource consumption. Consequently, this paradigm shift has come to alter the notion of a factory by many orders of magnitude and to create a new bridge between the built and natural world, as we employ nature’s evolutionary machinery to address our modern endeavours.Growth of the genetic toolbox and maturation of synthetic biology as a field has led to speculation about increasingly ambitious applications of writing biology with implications beyond biosynthesis. To date, most applications have been developed using microbes because they are less complex, more well understood and easier to manipulate. Single‐celled organisms can be optimized for production of complicated organic molecules; however, other exploits of genetic engineering will target more ambitious feats and thus require engineering of more than a large monoculture of microbes. Applications of synthetic biology outside of the bioreactor can address such issues as health and longevity, challenges in industrial agriculture and farming, the degradation of natural habitats and the reclamation of limited natural resources.Scope and scale of these applications provide obvious obstacles to the development of effective biotechnologies, but a more immediate limitation to realizing these technologies is the relative lack of genetic tools and insights which would allow the tinkering and rewiring of more complex organisms such as animals and plants. However, because of the natural intimate interactions between higher eukaryotes and microbes and the effect of these on phenotype, it is our vision that a faster, more tractable route to the engineering animal and plant phenotypes is via engineering their microbiomes.     

When are alternative stable states more likely to occur?

T. Fukami and W. G. Lee argue that the logical expectation from ecological theory is that competitively-structured assemblages will be more likely to exhibit alternative stable states than abiotically-structured assemblages. We suggest that there are several important misinterpretations in their arguments, and that the substance of their hypothesis has both a weak basis in ecological theory and is not supported by empirical evidence which shows that alternative stable states occur more frequently in natural systems subject to moderate- to harsh abiotic extremes. While this debate is founded in ecological theory, it has important applied implications for restoration management. Sound theoretical predictions about when to expect alternative stable states can only aid more effective restoration if theoretical expectations can be shown to translate into predictable empirical outcomes. If strongly abiotically- or disturbance-structured systems are more likely to exhibit catastrophic phase shifts in community structure that can be resilient to management efforts, then restoration ecologists will need to treat these systems differently in terms of the types of management inputs that are required.     

Pooled sample-based GWAS: a cost-effective alternative for identifying colorectal and prostate cancer risk variants in the Polish population

Background

Prostate cancer (PCa) and colorectal cancer (CRC) are the most commonly diagnosed cancers and cancer-related causes of death in Poland. To date, numerous single nucleotide polymorphisms (SNPs) associated with susceptibility to both cancer types have been identified, but their effect on disease risk may differ among populations.

Methods

To identify new SNPs associated with PCa and CRC in the Polish population, a genome-wide association study (GWAS) was performed using DNA sample pools on Affymetrix Genome-Wide Human SNP 6.0 arrays. A total of 135 PCa patients and 270 healthy men (PCa sub-study) and 525 patients with adenoma (AD), 630 patients with CRC and 690 controls (AD/CRC sub-study) were included in the analysis. Allele frequency distributions were compared with t-tests and χ²-tests. Only those significantly associated SNPs with a proxy SNP (p<0.001; distance of 100 kb; r²>0.7) were selected. GWAS marker selection was conducted using PLINK. The study was replicated using extended cohorts of patients and controls. The association with previously reported PCa and CRC susceptibility variants was also examined. Individual patients were genotyped using TaqMan SNP Genotyping Assays.

Results

The GWAS selected six and 24 new candidate SNPs associated with PCa and CRC susceptibility, respectively. In the replication study, 17 of these associations were confirmed as significant in additive model of inheritance. Seven of them remained significant after correction for multiple hypothesis testing. Additionally, 17 previously reported risk variants have been identified, five of which remained significant after correction.

Conclusion

Pooled-DNA GWAS enabled the identification of new susceptibility loci for CRC in the Polish population. Previously reported CRC and PCa predisposition variants were also identified, validating the global nature of their associations. Further independent replication studies are required to confirm significance of the newly uncovered candidate susceptibility loci.     

Jasmonic Acid-Induced Morphological Changes are Reflected in Auxin Metabolism of Beans Grown in vitro

Auxins were analysed in roots, stems with apical shoots, and leaves of beans (Phaseolus vulgaris L. cv. Zorin) cultured for three weeks on media supplied with different concentrations of jasmonic acid (JA). Morphology changes induced by applied JA were reflected in tissue-specific changes of auxins. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of intravenous N-acetylcysteine infusion on time to fatigue and potassium regulation during prolonged cycling exercise.

The production of reactive oxygen species in skeletal muscle is linked with muscle fatigue. This study investigated whether the antioxidant compound N-acetylcysteine (NAC) augments time to fatigue during prolonged, submaximal cycling exercise. Seven men completed a double-blind, crossover study, receiving NAC or placebo before and during cycling exercise, comprising 45 min at 70% of peak oxygen consumption (Vo2 peak) and then to fatigue at 90% Vo2 peak. NAC was intravenously infused at 125 mg.kg-1.h-1 for 15 min and then 25 mg.kg-1.h-1 for 20 min before and throughout exercise, which was continued until fatigue. Arterialized venous blood was analyzed for NAC concentration, hematology, and plasma electrolytes. NAC induced no serious adverse reactions and did not affect hematology, acid-base status, or plasma electrolytes. Time to fatigue was reproducible in preliminary trials (coefficient of variation 7.4 +/- 1.2%) and was not augmented by NAC (NAC 14.6 +/- 4.5 min; control 12.8 +/- 5.4 min). However, time to fatigue during NAC trials was correlated with Vo2 peak (r = 0.78; P < 0.05), suggesting that NAC effects on performance may be dependent on training status. The rise in plasma K+ concentration at fatigue was attenuated by NAC (P < 0.05). The ratio of rise in K+ concentration to work and the percentage change in time to fatigue tended to be inversely related (r = -0.71; P < 0.07). Further research is required to clarify a possible training status-dependent effect of NAC on muscle performance and K+ regulation.     

Nitrogen deposition to and cycling in a deciduous forest

The project described here seeks to answer questions regarding the role increased nitrogen (N) deposition is playing in enhanced carbon (C) sequestration in temperate mid-latitude forests, using detailed measurements from an AmeriFlux tower in southern Indiana (Morgan-Monroe State Forest, or MMSF). The measurements indicate an average atmosphere-surface N flux of approximately 6 mg-N m(-2) day(-1) during the 2000 growing season, with approximately 40% coming from dry deposition of ammonia (NH3), nitric acid (HNO3), and particle-bound N. Wet deposition and throughfall measurements indicate significant canopy uptake of N (particularly NH4+) at the site, leading to a net canopy exchange (NCE) of -6 kg-N ha(-1) for the growing season. These data are used in combination with data on the aboveground C:N ratio, litterfall flux, and soil net N mineralization rates to indicate the level of potential perturbation of C sequestration at this site.     

Plant community dynamics, nutrient cycling, and alternative stable equilibria in peatlands

Although observational data and experiments suggest that carbon flux and storage in peatlands are controlled by hydrology and/or nutrient availability, we lack a rigorous theory to account for the roles that different plant species or life-forms, particularly mosses, play in carbon and nutrient flux and storage and how they interact with different hydrologic sources of nutrients. We construct and analyze a model of peatlands that sheds some light on this problem. The model is a set of six coupled differential equations that define the flow of nutrients from moss and vascular plants to their litters, then to peat, and finally to an inorganic nutrient resource pool. We first analyze a simple version of this model (model 1) in which all nutrient input is from precipitation and enters the moss compartment directly, mimicking the dynamics of ombrotrophic bogs. There is a transcritical bifurcation that results in a switch of stability between two equilibrium bog communities: a moss monoculture and a community where mosses and vascular plants coexist. The bifurcation depends on the magnitudes of the input/output budget of the peatland and the life-history traits of the plants. We generalize model 1 to model 2 by dividing nutrient inputs between precipitation and groundwater, thus also allowing the development of minerotrophic fens that receive nutrient subsidies from both groundwater and precipitation and adding intraspecific competition (self-limitation) terms for both moss and vascular plants. Partitioning precipitation inputs between moss and the nutrient pool resulted in the greatest changes in model behavior, including the appearance of a lake and a vascular plant monoculture as well as the moss monoculture and coexistence equilibrium. As with model 1, these solutions are separated by transcritical bifurcations depending on critical combinations of parameters determining the input-output budget of the peatland as well as the life-history characteristics of the plant species. Model 2 also allowed for an early transient spike in vascular plant dominance followed by approach to near moss monoculture and then eventual approach to coexistence equilibrium. This generalized model mimics the broad features of successional development of peatlands from fens to bogs often found in the paleorecords of peat cores.     

Cellular responses to a prolonged delay in mitosis are determined by a DNA damage response controlled by Bcl-2 family proteins

Anti-cancer drugs that disrupt mitosis inhibit cell proliferation and induce apoptosis, although the mechanisms of these responses are poorly understood. Here, we characterize a mitotic stress response that determines cell fate in response to microtubule poisons. We show that mitotic arrest induced by these drugs produces a temporally controlled DNA damage response (DDR) characterized by the caspase-dependent formation of γH2AX foci in non-apoptotic cells. Following exit from a delayed mitosis, this initial response results in activation of DDR protein kinases, phosphorylation of the tumour suppressor p53 and a delay in subsequent cell cycle progression. We show that this response is controlled by Mcl-1, a regulator of caspase activation that becomes degraded during mitotic arrest. Chemical inhibition of Mcl-1 and the related proteins Bcl-2 and Bcl-x_L by a BH3 mimetic enhances the mitotic DDR, promotes p53 activation and inhibits subsequent cell cycle progression. We also show that inhibitors of DDR protein kinases as well as BH3 mimetics promote apoptosis synergistically with taxol (paclitaxel) in a variety of cancer cell lines. Our work demonstrates the role of mitotic DNA damage responses in determining cell fate in response to microtubule poisons and BH3 mimetics, providing a rationale for anti-cancer combination chemotherapies.     

Saliva samples are a viable alternative to blood samples as a source of DNA for high throughput genotyping

ABSTRACT: BACKGROUND: The increasing trend for incorporation of biological sample collection within clinical trials requires sample collection procedures which are convenient and acceptable for both patients and clinicians. This study investigated the feasibility of using saliva-extracted DNA in comparison to blood-derived DNA, across two genotyping platforms: Applied Biosystems Taqman TM and Illumina Beadchip TM genome-wide arrays. METHOD: Patients were recruited from the Pharmacogenetics of Breast Cancer Chemotherapy (PGSNPS) study. Paired blood and saliva samples were collected from 79 study participants. The Oragene DNA Self-Collection kit (DNAgenotek(R)) was used to collect and extract DNA from saliva. DNA from EDTA blood samples (median volume 8 ml) was extracted by GenProbe, Livingstone, UK. DNA yields, standard measures of DNA quality, genotype call rates and genotype concordance between paired, duplicated samples were assessed. RESULTS: Total DNA yields were lower from saliva (mean 24 ug, range 0.2-52 ug) than from blood (mean 210 ug, range 58-577 ug) and a 2-fold difference remained after adjusting for the volume of biological material collected. Protein contamination and DNA fragmentation measures were greater in saliva DNA. 78/79 saliva samples yielded sufficient DNA for use on Illumina Beadchip arrays and using Taqman assays. Four samples were randomly selected for genotyping in duplicate on the Illumina Beadchip arrays. All samples were genotyped using Taqman assays. DNA quality, as assessed by genotype call rates and genotype concordance between matched pairs of DNA was high (>97%) for each measure in both blood and saliva-derived DNA. CONCLUSION: We conclude that DNA from saliva and blood samples is comparable when genotyping using either Taqman assays or genome-wide chip arrays. Saliva sampling has the potential to increase participant recruitment within clinical trials, as well as reducing the resources and organisation required for multicentre sample collection.     

Influence of prolonged endurance cycling and recovery diet on intramuscular triglyceride content in trained males

Intramuscular triglycerides (IMTG) are assumed to form an important substrate source during prolonged endurance exercise in trained males. This study investigated the effects of endurance exercise and recovery diet on IMTG content in vastus lateralis muscle. Nine male cyclists were provided with a standardized diet for 3 days, after which they performed a 3-h exercise trial at a 55% maximum workload. Before and immediately after exercise and after 24 and 48 h of recovery, magnetic resonance spectroscopy (MRS) was performed to quantitate IMTG content. Muscle biopsies were taken after 48 h of recovery to determine IMTG content by using quantitative fluorescence microscopy. The entire procedure was performed two times; in one trial, a normal diet containing 39% energy (En%) as fat was provided (NF) and in the other a typical carbohydrate-rich athlete's diet (LF: 24 En% fat) was provided. During exercise, IMTG content decreased by 21.4 +/- 3.1%. During recovery, IMTG content increased significantly in the NF trial only, reaching preexercise levels within 48 h. In accord with MRS, fluorescence microscopy showed significantly higher IMTG content in the NF compared with the LF trial, with differences restricted to the type I muscle fibers (2.1 +/- 0.2 vs. 1.4 +/- 0.2% area lipid staining, respectively). In conclusion, IMTG content in the vastus lateralis muscle declines significantly during prolonged endurance exercise in male cyclists. When a normal diet is used, IMTG contents are subsequently repleted within 48 h of postexercise recovery. In contrast, IMTG repletion is impaired substantially when a typical, carbohydrate-rich athlete's diet is used. Data obtained by quantitative fluorescence microscopy correspond well with MRS results, implying that both are valid methods to quantify IMTG content.     

Influence of gender, menstrual phase, and oral contraceptive use on immunological changes in response to prolonged cycling.

This study determined the influence of gender, menstrual phase (MP), and oral contraceptive (OC) use on immunological changes in response to endurance exercise. Twelve women and 11 men similar in age, aerobic power, and activity level cycled for 90 min at 65% maximal aerobic power. Women were OC users (n = 6) or nonusers (NOC) and cycled during the follicular (Fol) and the luteal (Lut) phases. Venous blood was collected before and after exercise to determine leukocyte counts, IL-6 concentrations, and cortisol. Higher resting levels of neutrophils (approximately 1.5-fold) and cortisol (approximately 2.5-fold) were found in OC vs. NOC and men. Exercise-induced immune cell count and IL-6 changes were similar between men and NOC, except for an approximately 38% greater lymphocyte response in NOC vs. men (P = 0.07). Neutrophil, monocyte, and lymphocyte responses to exercise during Lut in OC were greater than during Fol and also greater than the responses in men (P < or = 0.003). Changes in immune cell counts were consistently greater during Lut in OC vs. NOC, regardless of MP, but only neutrophil responses reached statistical significance (P = 0.01). The exercise-induced change in IL-6 was approximately 80% greater in NOC vs. OC during Fol (P = 0.06), but it was similar between these groups during Lut. Cortisol changes with exercise were not different between groups or MP. These results highlight the necessity to control for gender, and in particular OC use, when designing studies evaluating exercise and immunology.