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Search Results: 1 - 10 of 219497 matches for " C. Hauton "
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The subtle effects of sea water acidification on the amphipod Gammarus locusta
C. Hauton, T. Tyrrell,J. Williams
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: We report an investigation of the effects of increases in pCO2 on the survival, growth and molecular physiology of the neritic amphipod Gammarus locusta which has a cosmopolitan distribution in estuaries. Amphipods were reared from juvenile to mature adult in laboratory microcosms at three different levels of pH in nominal range 8.1–7.6. Growth rate was estimated from weekly measures of body length. At sexual maturity the amphipods were sacrificed and assayed for changes in the expression of genes coding for a heat shock protein (hsp70 gene) and the metabolic enzyme glyceraldehyde-3-phosphate dehydrogenase (gapdh gene). The data show that the growth and survival of this species is not significantly impacted by a decrease in sea water pH of up to 0.5 units. Quantitative real-time PCR analysis indicated that there was no significant effect of growth in acidified sea water on the sustained expression of the hsp70 gene. There was a consistent and significant increase in the expression of the gapdh gene at a pH of ~7.5 which, when combined with observations from other workers, suggests that metabolic changes may occur in response to acidification. It is concluded that sensitive assays of tissue physiology and molecular biology should be routinely employed in future studies of the impacts of sea water acidification as subtle effects on the physiology and metabolism of coastal marine species may be overlooked in conventional gross "end-point" studies of organism growth or mortality.
The subtle effects of sea water acidification on the amphipod Gammarus locusta
C. Hauton,T. Tyrrell,J. Williams
Biogeosciences Discussions , 2009,
Abstract: We report an investigation of the effects of increases in pCO2 on the growth and molecular physiology of the neritic amphipod Gammarus locusta, which has a cosmopolitan distribution in estuaries. Amphipods were reared from juvenile to mature adult in laboratory microcosms at three different levels of pH in nominal range 8.1–7.6. Growth rate was estimated from weekly measures of body length. At sexual maturity the amphipods were sacrificed and assayed for changes in the expression of genes coding for a heat shock protein (hsp70 gene) and the metabolic enzyme glyceraldehyde-3-phosphate dehydrogenase (gapdh gene). The data show that the growth and survival rate of this species is not significantly impacted by a decrease in sea water pH of up to 0.5 units. Quantitative real-time PCR analysis indicated that there was no significant effect of growth in acidified sea water on the expression of the hsp70 gene. However, there was a consistent and significant increase in the expression of the gapdh gene at a pH of ~7.5 which indicated a possible disruption to oxidative metabolic processes. It was concluded that future predicted changes in sea water pH may have subtle effects on the physiology and metabolism of coastal and marine species which may be overlooked in studies of whole organism response.
Prenatal hypoxia induces increased cardiac contractility on a background of decreased capillary density
David Hauton, Victoria Ousley
BMC Cardiovascular Disorders , 2009, DOI: 10.1186/1471-2261-9-1
Abstract: Pregnant female wistar rats were exposed to hypoxia (12% oxygen, balance nitrogen) for days 10–20 of pregnancy. Pups were born into normal room air and weaned normally. At 10 weeks of age, hearts were excised under anaesthesia and underwent retrograde 'Langendorff' perfusion. Mechanical performance was measured at constant filling pressure (100 cm H2O) with intraventricular balloon. Left ventricular free wall was dissected away and capillary density estimated following alkaline phosphatase staining. Expression of SERCA2a and Nitric Oxide Synthases (NOS) proteins were estimated by immunoblotting.CHU significantly increased body mass (P < 0.001) compared with age-matched control rats but was without effect on relative cardiac mass. For incremental increases in left ventricular balloon volume, diastolic pressure was preserved. However, systolic pressure was significantly greater following CHU for balloon volume = 50 μl (P < 0.01) and up to 200 μl (P < 0.05). For higher balloon volumes systolic pressure was not significantly different from control. Developed pressures were correspondingly increased relative to controls for balloon volumes up to 250 μl (P < 0.05). Left ventricular free wall capillary density was significantly decreased in both epicardium (18%; P < 0.05) and endocardium (11%; P < 0.05) despite preserved coronary flow. Western blot analysis revealed no change to the expression of SERCA2a or nNOS but immuno-detectable eNOS protein was significantly decreased (P < 0.001) in cardiac tissue following chronic hypoxia in utero.These data offer potential mechanisms for poor recovery following ischaemia, including decreased coronary flow reserve and impaired angiogenesis with subsequent detrimental effects of post-natal cardiac performance.Prenatal hypoxia may be one of the most common insults to the fetus during pregnancy. Exposures can vary from acute short-term insults [1] to chronic exposures (chronic hypoxia in utero – CHU) and have different impacts on fetal
The Implications of Temperature-Mediated Plasticity in Larval Instar Number for Development within a Marine Invertebrate, the Shrimp Palaemonetes varians
Andrew Oliphant, Chris Hauton, Sven Thatje
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0075785
Abstract: Variations in larval instar number are common among arthropods. Here, we assess the implications of temperature-mediated variations in larval instar number for larval development time, larval growth rates, and juvenile dry weight within the palaemonid shrimp, Palaemonetes varians. In contrast with previous literature, which focuses on terrestrial arthropods, particularly model and pest species often of laboratory lines, we use wild shrimp, which differ in their life history from previous models. Newly-hatched P. varians larvae were first reared at 5, 10, 17, 25, and 30°C to assess their thermal scope for development. Larvae developed at 17, 25, and 30°C. At higher temperatures, larvae developed through fewer larval instars. Two dominant developmental pathways were observed; a short pathway of four instars and a long pathway of five instars. Longer developmental pathways of six to seven instars were rarely observed (mostly at lower temperatures) and consisted of additional instars as ‘repeat’ instars; i.e. little developmental advance over the preceding instar. To assess the implications of temperature-mediated variation in larval instar number, newly-hatched larvae were then reared at 15, 20, and 25°C. Again, the proportion of larvae developing through four instars increased with temperature. At all temperatures, larval development time and juvenile dry weight were greater for larvae developing through five instars. Importantly, because of the increasing proportion of larvae developing through four instars with increasing temperature, larval traits associated with this pathway (reduced development time and juvenile dry weight) became more dominant. As a consequence of increasing growth rate with temperature, and the shift in the proportion of larvae developing through four instars, juvenile dry weight was greatest at intermediate temperatures (20°C). We conclude that at settlement P. varians juveniles do not follow the temperature-size rule; this is of importance for life-history ecology in response to environmental change, as well as for aquaculture applications.
Phocid Seal Leptin: Tertiary Structure and Hydrophobic Receptor Binding Site Preservation during Distinct Leptin Gene Evolution
John A. Hammond, Chris Hauton, Kimberley A. Bennett, Ailsa J. Hall
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035395
Abstract: The cytokine hormone leptin is a key signalling molecule in many pathways that control physiological functions. Although leptin demonstrates structural conservation in mammals, there is evidence of positive selection in primates, lagomorphs and chiropterans. We previously reported that the leptin genes of the grey and harbour seals (phocids) have significantly diverged from other mammals. Therefore we further investigated the diversification of leptin in phocids, other marine mammals and terrestrial taxa by sequencing the leptin genes of representative species. Phylogenetic reconstruction revealed that leptin diversification was pronounced within the phocid seals with a high dN/dS ratio of 2.8, indicating positive selection. We found significant evidence of positive selection along the branch leading to the phocids, within the phocid clade, but not over the dataset as a whole. Structural predictions indicate that the individual residues under selection are away from the leptin receptor (LEPR) binding site. Predictions of the surface electrostatic potential indicate that phocid seal leptin is notably different to other mammalian leptins, including the otariids. Cloning the grey seal leptin binding domain of LEPR confirmed that this was structurally conserved. These data, viewed in toto, support a hypothesis that phocid leptin divergence is unlikely to have arisen by random mutation. Based upon these phylogenetic and structural assessments, and considering the comparative physiology and varying life histories among species, we postulate that the unique phocid diving behaviour has produced this selection pressure. The Phocidae includes some of the deepest diving species, yet have the least modified lung structure to cope with pressure and volume changes experienced at depth. Therefore, greater surfactant production is required to facilitate rapid lung re-inflation upon surfacing, while maintaining patent airways. We suggest that this additional surfactant requirement is met by the leptin pulmonary surfactant production pathway which normally appears only to function in the mammalian foetus.
Regulation of Lipogenesis by Glucocorticoids and Insulin in Human Adipose Tissue
Laura L. Gathercole, Stuart A. Morgan, Iwona J. Bujalska, David Hauton, Paul M. Stewart, Jeremy W. Tomlinson
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026223
Abstract: Patients with glucocorticoid (GC) excess, Cushing's syndrome, develop a classic phenotype characterized by central obesity and insulin resistance. GCs are known to increase the release of fatty acids from adipose, by stimulating lipolysis, however, the impact of GCs on the processes that regulate lipid accumulation has not been explored. Intracellular levels of active GC are dependent upon the activity of 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) and we have hypothesized that 11β-HSD1 activity can regulate lipid homeostasis in human adipose tissue (Chub-S7 cell line and primary cultures of human subcutaneous (sc) and omental (om) adipocytes. Across adipocyte differentiation, lipogenesis increased whilst β-oxidation decreased. GC treatment decreased lipogenesis but did not alter rates of β-oxidation in Chub-S7 cells, whilst insulin increased lipogenesis in all adipocyte cell models. Low dose Dexamethasone pre-treatment (5 nM) of Chub-S7 cells augmented the ability of insulin to stimulate lipogenesis and there was no evidence of adipose tissue insulin resistance in primary sc cells. Both cortisol and cortisone decreased lipogenesis; selective 11β-HSD1 inhibition completely abolished cortisone-mediated repression of lipogenesis. GCs have potent actions upon lipid homeostasis and these effects are dependent upon interactions with insulin. These in vitro data suggest that manipulation of GC availability through selective 11β-HSD1 inhibition modifies lipid homeostasis in human adipocytes.
A Picture on the Wall: Innovative Mapping Reveals Cold-Water Coral Refuge in Submarine Canyon
Veerle A. I. Huvenne, Paul A. Tyler, Doug G. Masson, Elizabeth H. Fisher, Chris Hauton, Veit Hühnerbach, Timothy P. Le Bas, George A. Wolff
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028755
Abstract: Cold-water corals are azooxanthellate species found throughout the ocean at water depths down to 5000 m. They occur in patches, reefs or large mound structures up to 380 m high, and as ecosystem engineers create important habitats for a diverse fauna. However, the majority of these habitats are now within reach of deep-sea bottom trawling. Many have been severely damaged or are under threat, despite recent protection initiatives. Here we present a cold-water coral habitat type that so far has been overlooked – quite literally – and that has received minimal impact from human activities. Vertical and overhanging cliffs in deep-sea canyons, revealed using an innovative approach to marine habitat mapping, are shown to provide the perfect substratum for extensive cold-water coral-based communities. Typical canyon-related processes, including locally enhanced internal tides and focussed downslope organic carbon transport, provide favourable environmental conditions (current regime, food input) to sustain the communities, even outside the optimal depth and density envelopes reported elsewhere in the NE Atlantic. Our findings show that deep-sea canyons can form natural refuges for faunal communities sensitive to anthropogenic disturbance, and have the potential to fulfil the crucial role of larval sources for the recolonisation of damaged sites elsewhere on the margin.
ВПЛИВ Х М ЧНОГО СКЛАДУ НА ТИСК НАСИЧЕНО ПАРИ В МОТОРНИХ Б ОЛОГ ЧНИХ ПАЛИВАХ The influence of chemical composition on the saturated vapor pressure in biological motor fuels Влияние химического состава на давление насыщенного пара в моторных биологических топливах
?.В. Полунк?н,C.О. Зубенко,О.О. Гайдай,А.В. Струнгар
Proceedings of National Aviation University , 2010,
Abstract: Розглянуто вплив випаровуваност альтернативних палив на р шення проблеми холодного пуску двигуна за рахунок використання пропан-бутаново сум ш для п двищення тиску насичено пари. Volatility fuels fraction of the estimated parameters and letkosti. Volatility characterizes the ability to switch fuels in vaporous state. Selecting indicators to assess the volatility depends on the chemical composition of fuel. The main measure letkosti etanolnogo fuel is vapor pressure. The most simple and cost-effective to improve cold start is putting in fuel lehkoletyuchyh components: butane, izopentanu, gas and other petroleum. It was investigated the influence of DEE on alcohol-gasoline blend, the results show that DEE positive impact on increasing vapor pressure to the desired minimum for starting the engine. But because the ether to 19%, then at such high levels can actively formed peroxide compounds, which is undesirable. Very promising is the use of propane-butane gas mixture as lehkoletyuchoyi gaseous component. Butanizovani spirit-petrol mixture can be recommended for use as alternative fuel vehicles after further study of their stability and himmotolohichnyh characteristics. Автомобильные бензины и альтернативные биологические топлива на основе этанола преимущественно предназначены для применения в двигателях внутреннего сгорания. При использовании альтернативного биологического топлива, особенно этанольного, возникает проблема недостаточной испаряемости бензина при низкой температуре, в результате чего в холодное время года двигатель может не запуститься. Пусковые свойства бензина зависят от содержания в них летучих фракций или летучих соединений. Проблему холодного запуска предлагается решать за счет использования пропан-бутановой смеси для повышения давления насыщенного пара. Для перспективного применения газов пропан-бутановой смеси легколетучего газообразного компонента необходимы дальнейшие исследования стабилизации такой композиции.
Strategic trends of development of the Lithuanian aviation in the light of Euro-integration processes Стратегические направления развития авиации литвы в свете евроинтеграции процессов СТРАТЕГ ЧНИЙ НАПРЯМ РОЗВИТКУ АВ АЦ ЛИТВИ У СВ ТЛИ ВРО НТЕГРАЦ ЙНИХ ПРОЦЕС В
Й. Станкунаc
Proceedings of National Aviation University , 2004,
Abstract: The factors having an effect on the system of air transport in the Republic of Lithuania in connection with Lithuania’s membership in the European Union are discussed. The structure of the system of air transport of the country is presented, an analysis of the current situation and a strategic analysis of the development of the system is made, and the measures addressed at the long-range perspective are proposed. Рассмотрены факторы, действующие в системе воздушного транспорта Литовской Республики после вступления в Европейский Союз. Приведена структура системы воздушного транспорта страны и выполнен стратегический анализ развития транспортной системы на долгосрочную перспективу. Розглянуто чинники, що д ють у систем пов тряного транспорту Литовсько Республ ки п сля вступу в вропейський Союз. Подано структуру систем пов тряного транспорту кра ни та виконано стратег чний анал з розвитку транспортно системи на довгострокову перспективу.
LIMIT DISTRIBUTION OF A RANK OF RANDOM SATURATED MATRIX ABOVE A FIELD GF(2) ПРЕДЕЛЬНОЕ РАСПРЕДЕЛЕНИЕ РАНГА СИЛЬНОЗАПОЛНЕННОЙ СЛУЧАЙНОЙ МАТРИЦЫ НАД ПОЛЕМ GF(2) ГРАНИЧНИЙ РОЗПОД Л РАНГУ СИЛЬНОЗАПОВНЕНО ВИПАДКОВО МАТРИЦ В ПОЛ GF(2)
C.В. Поперешняк
Proceedings of National Aviation University , 2012,
Abstract: In this paper a theorem on the asymptotic distribution of rank of random matrices in the field GF (2) of independent random -D lines, the absence in it of unity lines and the assumption that the difference between the number of rows and number of columns of the matrix is a fixed number of random characters, . Получена теорема про асимптотику распределения ранга случайной матрицы над полем GF(2), которая состоит из независимых случайных -мерных строк, при условии отсутствия в ней единичных линий и в предположении, что разница между числом строк и числом столбцов матрицы фиксированное число произвольного знака, . Отримано теорему про асимптотику розпод лу рангу випадково матриц в пол GF(2) з незалежних випадкових -вим рних рядк в за умови в дсутност в н й одиничних л н й та в припущенн , що р зниця м ж числом рядк в та числом стовпц в матриц ф ксоване число дов льного знаку,
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