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Search Results: 1 - 10 of 336349 matches for " Christopher S. Shaw "
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Definable choice for a class of weakly o-minimal theories
Michael C. Laskowski,Christopher S. Shaw
Mathematics , 2015,
Abstract: Given an o-minimal structure ${\mathcal M}$ with a group operation, we show that for a properly convex subset $U$, the theory of the expanded structure ${\mathcal M}'=({\mathcal M},U)$ has definable Skolem functions precisely when ${\mathcal M}'$ is valuational. As a corollary, we get an elementary proof that the theory of any such ${\mathcal M}'$ does not satisfy definable choice.
Early Exposure to Environmental Toxin Contributes to Neuronal Vulnerability and Axonal Pathology in a Model of Familial ALS  [PDF]
Grace Lee, Christopher A. Shaw
Neuroscience & Medicine (NM) , 2012, DOI: 10.4236/nm.2012.34050
Abstract: Adult onset amyotrophic lateral sclerosis (ALS) arises due to progressive and irreversible functional deficits to the central nervous system, specifically the loss of motor neurons. Sporadic ALS causality is not well understood, but is almost certainly of multifactorial origin involving a combination of genetic and environmental factors. The discovery of endemic ALS in the native Chamorro population of Guam during the 1950s and the co-occurrence of Parkinsonism and dementia in some patients led to searches for environmental toxins that could be responsible. In the present paper, we report that an environmental neurotoxin enhances mutant superoxide dismutase (SOD)-induced spinal motor neuron death and pathology and induces motor axon abnormalities. These results cumulatively confirm earlier findings that exposure to an environmental toxin is sufficient to produce the disease phenotype and indicate a role for gene-environment interaction in some forms of the disease.
Beneficial Effects of Resistance Exercise on Glycemic Control Are Not Further Improved by Protein Ingestion
Leigh Breen, Andrew Philp, Christopher S. Shaw, Asker E. Jeukendrup, Keith Baar, Kevin D. Tipton
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0020613
Abstract: Purpose To investigate the mechanisms underpinning modifications in glucose homeostasis and insulin sensitivity 24 h after a bout of resistance exercise (RE) with or without protein ingestion. Methods Twenty-four healthy males were assigned to a control (CON; n = 8), exercise (EX; n = 8) or exercise plus protein condition (EX+PRO; n = 8). Muscle biopsy and blood samples were obtained at rest for all groups and immediately post-RE (75% 1RM, 8×10 repetitions of leg-press and extension exercise) for EX and EX+PRO only. At 24 h post-RE (or post-resting biopsy for CON), a further muscle biopsy was obtained. Participants then consumed an oral glucose load (OGTT) containing 2 g of [U-13C] glucose during an infusion of 6, 6-[2H2] glucose. Blood samples were obtained every 10 min for 2 h to determine glucose kinetics. EX+PRO ingested an additional 25 g of intact whey protein with the OGTT. A final biopsy sample was obtained at the end of the OGTT. Results Fasted plasma glucose and insulin were similar for all groups and were not different immediately post- and 24 h post-RE. Following RE, muscle glycogen was 26±8 and 19±6% lower in EX and EX+PRO, respectively. During OGTT, plasma glucose AUC was lower for EX and EX+PRO (75.1±2.7 and 75.3±2.8 mmol·L?1:120 min, respectively) compared with CON (90.6±4.1 mmol·L?1:120 min). Plasma insulin response was 13±2 and 21±4% lower for EX and CON, respectively, compared with EX+PRO. Glucose disappearance from the circulation was ~12% greater in EX and EX+PRO compared with CON. Basal 24 h post-RE and insulin-stimulated PAS-AS160/TBC1D4 phosphorylation was greater for EX and EX+PRO. Conclusions Prior RE improves glycemic control and insulin sensitivity through an increase in the rate at which glucose is disposed from the circulation. However, co-ingesting protein during a high-glucose load does not augment this response at 24 h post-exercise in healthy, insulin-sensitive individuals.
Responses of Grassland Production to Single and Multiple Global Environmental Changes
Jeffrey S. Dukes,Nona R. Chiariello,Elsa E. Cleland,Lisa A. Moore,M. Rebecca Shaw,Susan Thayer,Todd Tobeck,Harold A. Mooney,Christopher B. Field
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0030319
Abstract: In this century, increasing concentrations of carbon dioxide (CO2) and other greenhouse gases in the Earth's atmosphere are expected to cause warmer surface temperatures and changes in precipitation patterns. At the same time, reactive nitrogen is entering natural systems at unprecedented rates. These global environmental changes have consequences for the functioning of natural ecosystems, and responses of these systems may feed back to affect climate and atmospheric composition. Here, we report plant growth responses of an ecosystem exposed to factorial combinations of four expected global environmental changes. We exposed California grassland to elevated CO2, temperature, precipitation, and nitrogen deposition for five years. Root and shoot production did not respond to elevated CO2 or modest warming. Supplemental precipitation led to increases in shoot production and offsetting decreases in root production. Supplemental nitrate deposition increased total production by an average of 26%, primarily by stimulating shoot growth. Interactions among the main treatments were rare. Together, these results suggest that production in this grassland will respond minimally to changes in CO2 and winter precipitation, and to small amounts of warming. Increased nitrate deposition would have stronger effects on the grassland. Aside from this nitrate response, expectations that a changing atmosphere and climate would promote carbon storage by increasing plant growth appear unlikely to be realized in this system.
Responses of Grassland Production to Single and Multiple Global Environmental Changes
Jeffrey S Dukes ,Nona R Chiariello,Elsa E Cleland,Lisa A Moore,M. Rebecca Shaw,Susan Thayer,Todd Tobeck,Harold A Mooney,Christopher B Field
PLOS Biology , 2005, DOI: 10.1371/journal.pbio.0030319
Abstract: In this century, increasing concentrations of carbon dioxide (CO2) and other greenhouse gases in the Earth's atmosphere are expected to cause warmer surface temperatures and changes in precipitation patterns. At the same time, reactive nitrogen is entering natural systems at unprecedented rates. These global environmental changes have consequences for the functioning of natural ecosystems, and responses of these systems may feed back to affect climate and atmospheric composition. Here, we report plant growth responses of an ecosystem exposed to factorial combinations of four expected global environmental changes. We exposed California grassland to elevated CO2, temperature, precipitation, and nitrogen deposition for five years. Root and shoot production did not respond to elevated CO2 or modest warming. Supplemental precipitation led to increases in shoot production and offsetting decreases in root production. Supplemental nitrate deposition increased total production by an average of 26%, primarily by stimulating shoot growth. Interactions among the main treatments were rare. Together, these results suggest that production in this grassland will respond minimally to changes in CO2 and winter precipitation, and to small amounts of warming. Increased nitrate deposition would have stronger effects on the grassland. Aside from this nitrate response, expectations that a changing atmosphere and climate would promote carbon storage by increasing plant growth appear unlikely to be realized in this system.
Mining non-model genomic libraries for microsatellites: BAC versus EST libraries and the generation of allelic richness
Christopher K Ellison, Kerry L Shaw
BMC Genomics , 2010, DOI: 10.1186/1471-2164-11-428
Abstract: 288 SSR loci were screened in the rapidly radiating Hawaiian swordtail cricket genus Laupala. SSRs were more densely distributed and contained longer repeat structures in BAC library-derived sequence than in EST library-derived sequence, although neither repeat density nor length was exceptionally elevated despite the relatively large genome size of Laupala. A non-random distribution favoring AT-rich SSRs was observed. Allelic diversity of SSRs was positively correlated with repeat length and was generally higher in AT-rich repeat motifs.The first large-scale survey of Orthopteran SSR allelic diversity is presented. Selection contributes more strongly to the size and density distributions of SSR loci derived from EST library sequence than from BAC library sequence, although all SSRs likely are subject to similar physical and structural constraints, such as slippage of DNA replication machinery, that may generate increased allelic diversity in AT-rich sequence motifs. Although in silico approaches work well for SSR locus identification in both EST and BAC libraries, BAC library sequence and AT-rich repeat motifs are generally superior SSR development resources for most applications.Microsatellites, or simple sequence repeats (SSRs), are common features of eukaryotic genomes and can be characterized as generally short, repeated nucleotide sequence elements arrayed in tandem and flanked by non-repetitive regions (reviewed in [1]). SSRs often harbor high levels of polymorphism in terms of repeat number and have been developed into one of the most common classes of genetic markers due to their high degree of reproducibility, ubiquity, codominance, and variability among individuals [2-4]. The multi-allelic nature of SSR loci is thought to derive principally from errors occurring due to slipped-strand mispairing during DNA replication [5-8], however, SSRs may also be generated via alternative means, such as retrotransposition events, interhelical junctions forming during c
Analogie tussen prosesse in fisiologie en ingenieurswese
I. S. Shaw
Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie , 2002, DOI: 10.4102/satnt.v21i2.229
Abstract: Fisiologie en ingenieurswese as studievakke word deesdae gewoonlik deur verskillende universiteitsdepartemente en selfs in verskillende fakulteite aangebied. Ten spyte van die groot verskille tussen die ooreenkomstige vaktale en metodologie bestaan daar baie interessante en insiggewende analogie tussen o nskynlik onverwante onderwerpe wat in hierdie vakrigtings voorkom. Daar is ook ’n onlangse poging om vakpersoneel te ontwikkel wat in albei vakke vaardig is en wat fisiologiese asook ingenieursterminologie kan verstaan en in ’n skeppende manier kan toepas. Selfs mense wat in fisiologie, geneeskunde, dierkunde en aan die ander kant in elektroniese, beheertegniese of meganiese ingenieurswese oor etlike jare se ervaring beskik, het dikwels ’n behoefte aan addisionele kennis in wedersydse vakrigtings ontdek. Die doel van hierdie werk is om belangstelling in hierdie verband deur die uiteensetting van besonder treffende gevalle van analogie te wek. Abstract Analogies between processes in physiology and engineering Physiology and engineering as fields of study are nowadays lectured at different university departments and even different faculties. Despite the great differences between the corresponding terminologies and methodologies, there exist very interesting and insight- provoking analogies between seemingly unrelated subjects encountered in these fields. There is also an emerging effort to develop experts that are familiar with both physiological and engineering terminologies and that are also able to apply them in a creative manner. Even people with many years of experience on the one hand in physiology, medicine, zoology and on the other hand, in electronic, control and mechanical engineering often have the need for additional knowledge in their mutual fields of endeavour . The purpose of this work is to engender an interest in this respect by pointing out especially pertinent cases of analogies.
SELF-REPORTED DIETARY INTAKE FOLLOWING ENDURANCE, RESISTANCE AND CONCURRENT ENDURANCE AND RESISTANCE TRAINING
Brandon S. Shaw,Ina Shaw,Gregory A. Brown
Journal of Sports Science and Medicine , 2008,
Abstract: With regards to obesity-related disease the impact of exercise training on health depends on the ability of exercise to promote a negative energy balance. Exercise's effect on promoting a negative energy balance is more likely to occur if exercise can induce a favourable dietary intake such as a reduced relative fat content in the diet. As such, the aim of this study was to evaluate and compare the effectiveness of aerobic training, weight training and concurrent aerobic and weight training on self-reported dietary intake. The effects of 16 weeks of aerobic (n = 12), weight (n = 13) and concurrent aerobic and weight training (n = 13) on self-reported dietary intakes were compared in previously sedentary males using the computer-based Dietary Manager software programme. Only the concurrent aerobic and weight training group showed significant (p < 0.05) reductions in total kilocalories, carbohydrates, proteins and fats consumed while the aerobic training group showed significant reductions in fat intake at the completion of the experimental period (before: 91.0 ± 42.1g versus after: 77.1 ± 62.1g). However, no changes were observed in self-reported dietary intake in the weight training or non-exercising control groups. It is concluded that concurrent aerobic and weight training is the most effective mode of exercise at promoting a favourable improvement in self-reported dietary intake in the short term. This finding provides support for efforts to promote increases in overall physical activity in an attempt to modify the patterns of dietary intake
Cardiac output estimation using pulmonary mechanics in mechanically ventilated patients
Ashwath Sundaresan, J Chase, Christopher E Hann, Geoffrey M Shaw
BioMedical Engineering OnLine , 2010, DOI: 10.1186/1475-925x-9-80
Abstract: This paper examines combining models of diffusion resistance and lung mechanics, to help predict CO changes due to PEEP. The CO estimator uses an initial measurement of pulmonary shunt, and estimations of shunt changes due to PEEP to predict CO at different levels of PEEP. Inputs to the cardiac model are the PV loops from the ventilator, as well as the oxygen saturation values using known respiratory inspired oxygen content. The outputs are estimates of pulmonary shunt and CO changes due to changes in applied PEEP. Data from two published studies are used to assess and initially validate this model.The model shows the effect on oxygenation due to decreased CO and decreased shunt, resulting from increased PEEP. It concludes that there is a trade off on oxygenation parameters. More clinically importantly, the model also examines how the rate of CO drop with increased PEEP can be used as a method to determine optimal PEEP, which may be used to optimise MV therapy with respect to the gas exchange achieved, as well as accounting for the impact on the cardiovascular system and its management.Patients diagnosed with acute respiratory distress syndrome (ARDS) often experience pulmonary shunt or gas exchange abnormalities due to lack of recruited alveoli. Shunt also occurs when there is an increased thoracic pressure that restricts blood flow, thus reducing the gas exchange. The primary objective of mechanical ventilation (MV) is to improve the condition of the patient by increasing alveoli recruitment and thus also improving or optimising gas exchange.A common MV parameter used to optimise recruitment is the positive end expiratory pressure (PEEP). PEEP is used to prevent alveoli derecruitment at the end of the expiration cycle [1] and to maintain a level of oxygenation. However, clinicians often debate the optimal level of PEEP required [2-4]. In particular, the application of PEEP poses some unique problems that need to be addressed.First, the ranges of allowable PEEP for
Cholesteryl glucoside stimulates activation of protein kinase B/Akt in the motor neuron-derived NSC34 cell line
Ly Philip T.T.,Pelech Steven,Shaw Christopher A
Neurobiology of Lipids , 2008,
Abstract: Steryl glycosides and related compounds are commonly found in the environment and have been associated with neurodegenerative changes in vulnerable individuals. However, their mechanisms of action in mammalian cells have not been well investigated. In the present study the effects of cholesterol glucoside (CG), a variant form of steryl glycoside, was investigated in the motor neuron-derived NSC34 cell line. Prolonged treatment with CG was found to induce cell death in a dose- and time-dependent manner. However, transient exposure of CG preconditioned NSC34 cells for stress from serum deprivation. To study the signaling pathways activated by CG, we employed the Kinetworks KPSS 1.3 Phospho-site Screen to track the phosphorylation level of at least 35 diverse signaling proteins. The survival protein kinase B (PKB/Akt) displayed a 2-fold increase in phosphorylation at its Ser-473 activation site following CG stimulation. Akt signaling was important for conferring cytoprotection against serum deprivation-induced stress. Inhibition of phosphatidylinositol 3-kinase (PI3K), which indirectly triggers Akt stimulation, completely abolished CG preconditioning against serum deprivation. Our findings revealed that there may be a PI3K-independent pathway which also mediated Akt Ser-473 phosphorylation. Improved understanding of the mechanisms of action of CG should provide insights to the how other members of the steryl glycoside family induce toxicity in the mouse model of ALS-PDC, and how cells respond to these toxins.
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