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Search Results: 1 - 10 of 299757 matches for " Graham J. Howie "
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Pre- and Postnatal Nutritional Histories Influence Reproductive Maturation and Ovarian Function in the Rat
Deborah M. Sloboda, Graham J. Howie, Anthony Pleasants, Peter D. Gluckman, Mark H. Vickers
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006744
Abstract: Background While prepubertal nutritional influences appear to play a role in sexual maturation, there is a need to clarify the potential contributions of maternal and childhood influences in setting the tempo of reproductive maturation. In the present study we employed an established model of nutritional programming to evaluate the relative influences of prenatal and postnatal nutrition on growth and ovarian function in female offspring. Methods Pregnant Wistar rats were fed either a calorie-restricted diet, a high fat diet, or a control diet during pregnancy and/or lactation. Offspring then were fed either a control or a high fat diet from the time of weaning to adulthood. Pubertal age was monitored and blood samples collected in adulthood for endocrine analyses. Results We report that in the female rat, pubertal timing and subsequent ovarian function is influenced by the animal's nutritional status in utero, with both maternal caloric restriction and maternal high fat nutrition resulting in early pubertal onset. Depending on the offspring's nutritional history during the prenatal and lactational periods, subsequent nutrition and body weight gain did not further influence offspring reproductive tempo, which was dominated by the effect of prenatal nutrition. Whereas maternal calorie restriction leads to early pubertal onset, it also leads to a reduction in adult progesterone levels later in life. In contrast, we found that maternal high fat feeding which also induces early maturation in offspring was associated with elevated progesterone concentrations. Conclusions These observations are suggestive of two distinct developmental pathways leading to the acceleration of pubertal timing but with different consequences for ovarian function. We suggest different adaptive explanations for these pathways and for their relationship to altered metabolic homeostasis.
Timing of Maternal Exposure to a High Fat Diet and Development of Obesity and Hyperinsulinemia in Male Rat Offspring: Same Metabolic Phenotype, Different Developmental Pathways?
Graham J. Howie,Deborah M. Sloboda,Clare M. Reynolds,Mark H. Vickers
Journal of Nutrition and Metabolism , 2013, DOI: 10.1155/2013/517384
Abstract: Objective. Offspring born to mothers either fed an obesogenic diet throughout their life or restricted to pregnancy and lactation demonstrate obesity, hyperinsulinemia, and hyperleptinemia, irrespective of their postweaning diet. We examined whether timing of a maternal obesogenic diet results in differential regulation of pancreatic adipoinsular and inflammatory signaling pathways in offspring. Methods. Female Wistar rats were randomized into 3 groups: (1) control (CONT): fed a control diet preconceptionally and during pregnancy and lactation; (2) maternal high fat (MHF): fed an HF diet throughout their life and during pregnancy and lactation; (3) pregnancy and lactation HF (PLHF): fed a control diet throughout life until mating, then HF diet during pregnancy and lactation. Male offspring were fed the control diet postweaning. Plasma and pancreatic tissue were collected, and mRNA concentrations of key factors regulating adipoinsular axis signaling were determined. Results. MHF and PLHF offspring exhibited increased adiposity and were hyperinsulinemic and hyperleptinemic compared to CONT. Despite a similar anthropometric phenotype, MHF and PLHF offspring exhibited distinctly different expression for key pancreatic genes, dependent upon maternal preconceptional nutritional background. Conclusions. These data suggest that despite using differential signaling pathways, obesity in offspring may be an adaptive outcome of early life exposure to HF during critical developmental windows. 1. Introduction Early life events contribute substantially to the likelihood of an individual becoming obese, although underlying mechanisms are not well understood. Obesity in women of reproductive age (15 to 44 years) is increasing rapidly, and up to 50% of women in this age range in the USA are now either overweight or obese [1]. This has translated to an exponential increase in the prevalence of obesity during pregnancy with up to 20% of women entering pregnancy with a BMI which would define them as obese [2]. Obesity in pregnancy increases the risks for complications of pregnancy including miscarriage, hypertension, and gestational diabetes [3–5]. Furthermore, it is now well established that maternal obesity leads to an increased risk of obesity and metabolic and cardiovascular disorders in offspring [6–9]. In view of the rising prevalence of obesity in pregnancy and its association with adverse maternal and offspring outcomes, there is a great deal of interest in understanding the mechanistic pathways that link maternal obesity and excess maternal nutrition to increased
Self-Intersecting Periodic Curves in the Plane
J Howie,J F Toland
Mathematics , 2010,
Abstract: Suppose a smooth planar curve $\gamma$ is $2\pi$-periodic in the $x$ direction and the length of one period is $\ell$. It is shown that if $\gamma$ self-intersects, then it has a segment of length $\ell- 2\pi$ on which it self-intersects and somewhere its curvature is at least $2\pi/(\ell - 2\pi)$. The proof involves the projection $\Gamma$ of $\gamma$ onto a cylinder. (The complex relation between $\gamma$ and $\Gamma$ was recently observed analytically by T. M. Apostol and M. A. Mnatsakanian. When $\gamma$ is in general position there is a bijection between self-intersection points of $\gamma$ modulo the periodicity, and self-intersection points of $\Gamma$ with winding number 0 around the cylinder. However, our proof depends on the observation that a loop in $\Gamma$ with winding number 1 leads to a self-intersection point of $\gamma$.
Seifert fibred knot manifolds
J. A. Hillman,J. Howie
Mathematics , 2013,
Abstract: We consider the question of when is the closed manifold obtained by elementary surgery on an $n$-knot Seifert fibred over a 2-orbifold. After some observations on the classical case, we concentrate on the cases n=2 and 3. We have found a new family of 2-knots with torsion-free, solvable group, overlooked in earlier work. We know of no higher dimensional examples.
Factors Associated with Bovine Neonatal Pancytopenia (BNP) in Calves: A Case-Control Study
Sarah L. Lambton, Adrian D. Colloff, Richard P. Smith, George L. Caldow, Sandra F. E. Scholes, Kim Willoughby, Fiona Howie, Johanne Ellis-Iversen, Graham David, Alasdair J. C. Cook, Andrew Holliman
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0034183
Abstract: Bovine neonatal pancytopenia (BNP; previously known as idiopathic haemorrhagic diathesis and commonly known as bleeding calf syndrome) is a novel haemorrhagic disease of young calves which has emerged in a number of European countries during recent years. Data were retrospectively collected during June to November 2010 for 56 case calves diagnosed with BNP between 17 March and 7 June of the same year. These were compared with 58 control calves randomly recruited from herds with no history of BNP. Multivariable logistic regression analysis showed that increased odds of a calf being a BNP case were associated with its dam having received PregSure? BVD (Pfizer Animal Health) vaccination prior to the birth of the calf (odds ratio (OR) 40.78, p<0.001) and its herd of origin being located in Scotland (OR 9.71, p = 0.006). Decreased odds of a calf being a BNP case were associated with the calf having been kept outside (OR 0.11, p = 0.006). The longer that a cattle herd had been established on the farm was also associated with decreased odds of a calf in that herd being a BNP case (OR 0.97, p = 0.011).
Modeling microbial survival in buildup biofilm for complex medical devices
Michelle J Alfa, Rosemarie Howie
BMC Infectious Diseases , 2009, DOI: 10.1186/1471-2334-9-56
Abstract: Using the MBEC (Minimum Biofilm Eradication Concentration) system, a unique modelling approach was developed to evaluate microbial survival in BBF formed by repetitive cycles of drying, disinfectant exposure and re-exposure to the test organism. This model mimics the cumulative effect of the reprocessing protocol on flexible endoscopes. Glutaraldehyde (GLUT) and accelerated hydrogen peroxide (AHP) were evaluated to assess the killing of microbes in TBF and BBF.The data showed that the combination of an organic matrix and aldehyde disinfection quickly produced a protective BBF that facilitated high levels of organism survival. In cross-linked BBF formed under high nutrient conditions the maximum colony forming units (CFU) reached ~6 Log10 CFU/peg. However, if an oxidizing agent was used for disinfection and if organic levels were kept low, organism survival did not occur. A key finding was that once established, the microbial load of BBF formed by GLUT exposure had a faster rate of accumulation than in TBF. The rate of biofilm survival post high-level disinfection (HLD) determined by the maximum Log10CFU/initial Log10CFU for E. faecalis and P. aeruginosa in BBF was 10 and 8.6 respectively; significantly different compared to a survival rate in TBF of ~2 for each organism. Data from indirect outgrowth testing demonstrated for the first time that there is organism survival in the matrix. Both TBF and BBF had surviving organisms when GLUT was used. For AHP survival was seen less frequently in BBF than in TBF.This BBF model demonstrated for the first time that survival of a wide range of microorganisms does occur in BBF, with significantly more rapid outgrowth compared to TBF. This is most pronounced when GLUT is used compared to AHP. The data supports the need for meticulous cleaning of reprocessed endoscopes since the presence of organic material and microorganisms prevents effective disinfection when GLUT and AHP are used. However, cross-linking agents like GLUT are n
Temporal variation in depth to water table and hydrochemistry in three raised bogs and their laggs in coastal British Columbia, Canada
S. A. Howie,H. J. van Meerveld
Hydrology and Earth System Sciences Discussions , 2012, DOI: 10.5194/hessd-9-14065-2012
Abstract: The laggs of three raised bogs in coastal British Columbia were studied in 2010–2012 to determine the temporal variation in depth to water table and hydrochemistry. The lagg is an integral, but rarely studied, part of a raised bog that helps to maintain the water mound in the bog and provides a buffer for runoff from adjacent mineral areas. Depth to water table measurements in 25 piezometers displayed similar annual fluctuations, with the highest water table in winter and the lowest at the end of summer. The smallest fluctuations in depth to water table were recorded closest to the bog centre, and the largest fluctuations in the laggs and adjacent mineral soil sites. Removal of a mature forest stand on one of the study transects resulted in a "watering-up" of the lagg site; the mean water level between August and November increased by 8 cm from 2010 to 2011, and by up to 27 cm during the driest time of the year. pH, pH-corrected electrical conductivity, and Na+ and Mg2+ concentrations varied little during the study period, whereas Ca2+, K+, Cl , and DOC concentrations and acidity were more variable.
Regional and local patterns in depth to water table, hydrochemistry, and peat properties of bogs and their laggs in coastal British Columbia
S. A. Howie,H. J. van Meerveld
Hydrology and Earth System Sciences Discussions , 2013, DOI: 10.5194/hessd-10-3143-2013
Abstract: In restoration planning for damaged raised bogs, the lagg at the bog margin is usually not given considerable weight and is sometimes disregarded entirely. However, the lagg is critical for the proper functioning of the restored bog, as it supports the water mound in the bog. In order to include the lagg in a restoration plan for a raised bog, it is necessary to understand the ecohydrological characteristics and functions of this transition zone. To this end, we studied 13 coastal British Columbia (BC) bogs and identified two different gradients in depth to water table, hydrochemistry, and peat properties: (1) a local bog expanse – bog margin gradient, and (2) a regional gradient related to climate and proximity to the ocean. Depth to water table generally increased across the transition from bog expanse to bog margin, but did not differ regionally. In the bog expanse, pH was above 4.2 in the Pacific Oceanic wetland region (cooler and wetter climate) and below 4.3 in the Pacific Temperate wetland region (warmer and drier climate). Both pH and pH-corrected electrical conductivity increased significantly across the transition from bog expanse to bog margin, though not in all cases. Sodium and magnesium concentrations were generally highest in exposed, oceanic bogs and lower in inland bogs. Ash content in peat samples increased across the bog expanse – bog margin transition, and appears to be a useful abiotic indicator of the location of the bog margin. These gradients highlight both local and regional diversity of bogs and their associated laggs. Knowledge of these gradients is critical if undisturbed bogs are used as templates for the restoration of damaged raised bogs.
The Very Young Type Ia Supernova 2013dy: Discovery, and Strong Carbon Absorption in Early-Time Spectra
WeiKang Zheng,Jeffrey M. Silverman,Alexei V. Filippenko,Daniel Kasen,Peter E. Nugent,Melissa Graham,Xiaofeng Wang,Stefano Valenti,Fabrizio Ciabattari,Patrick L. Kelly,Ori D. Fox,Isaac Shivvers,Kelsey I. Clubb,S. Bradley Cenko,Dave Balam,D. Andrew Howell,Eric Hsiao,Weidong Li,G. Howie Marion,David Sand,Jozsef Vinko,J. Craig Wheeler,JuJia Zhang
Physics , 2013, DOI: 10.1088/2041-8205/778/1/L15
Abstract: The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ~ 13.7 Mpc) was discovered by the Lick Observatory Supernova Search. Combined with a prediscovery detection by the Italian Supernova Search Project, we are able to constrain the first-light time of SN 2013dy to be only 0.10 +/- 0.05 d (2.4 +/- 1.2 hr) before the first detection. This makes SN 2013dy the earliest known detection of an SN Ia. We infer an upper limit on the radius of the progenitor star of R_0 < 0.25 R_sun, consistent with that of a white dwarf. The light curve exhibits a broken power law with exponents of 0.88 and then 1.80. A spectrum taken 1.63 d after first light reveals a C II absorption line comparable in strength to Si II. This is the strongest C II feature ever detected in a normal SN Ia, suggesting that the progenitor star had significant unburned material. The C II line in SN 2013dy weakens rapidly and is undetected in a spectrum 7 days later, indicating that C II is detectable for only a very short time in some SNe Ia. SN 2013dy reached a B-band maximum of M_B = -18.72 +/- 0.03 mag ~17.7 d after first light.
The Effects of Stabilized Urea and Split-Applied Nitrogen on Sunflower Yield and Oil Content  [PDF]
Christopher J. Graham, Jac J. Varco
American Journal of Plant Sciences (AJPS) , 2017, DOI: 10.4236/ajps.2017.88125
Abstract: Sunflower is an efficient nitrogen (N) accumulator due to its aggressive taproot and extensive root system. While N rate studies in sunflower have shown a yield response, the response is often highly variable and difficult to predict in many instances. Additionally, since most sunflower production is intended for the oil market, surplus nitrogen tends to decrease oil content. Therefore, it is critical to hone nitrogen rates to maximize both yield and oil production and to incorporate alternative approaches to fertilizer application, which includes timing and method of application. The objective of the present study was to assess the efficacy of a split-application of N at either the V4 or R1 growth stage to increase yield and/or oil content in sunflower. A second objective was to examine whether a urease inhibitor could be used to retain soil N longer and achieve a similar effect as a split-application. Studies were conducted at two locations over two growing seasons in South Dakota, USA. A target rate of 90 kg·ha-1 was applied as urea-ammonium nitrate (UAN) either as an at-planting application or split-applied. Overall, N additions did significantly increase yield over a control. On average, the urease inhibitor tended to increase grain yields over split-applying N at either growth stage, however, there was no statistical effect on either grain yield or oil content. Based on 15N analysis, approximately 27% of the N in the grain was derived from the UAN fertilizer, which indicates a relatively large reliance upon soil N for grain N content. The addition of a urease inhibitor significantly increased average fertilizer uptake by nearly 6% to 32.7%.
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