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David M Karl - One of the best experts on this subject based on the ideXlab platform.
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Metabolic Balance in the mixed layer of the oligotrophic north pacific ocean from diel changes in o2 ar saturation ratios
Geophysical Research Letters, 2015Co-Authors: Sara Ferron, Samuel T Wilson, Sandra Martinezgarcia, Paul D Quay, David M KarlAbstract:In situ measurements were made to determine oxygen (O2) Metabolic Balance in the upper oligotrophic ocean from diel changes in O2 to argon (Ar) ratios. The study took place during 13–24 March 2014, at the Hawaii Ocean Time-series Station ALOHA (A Long-term Oligotrophic Habitat Assessment), in the North Pacific Subtropical Gyre. Microbial community respiration and gross O2 production, estimated from in situ diel changes in O2/Ar saturation, agreed well with those calculated using other independent methods. Net oxygen production (NOP), estimated from in situ diel changes in O2/Ar saturation, showed large day-to-day variability. However, when averaged over the entire observational period, mean diel NOP was in relatively good agreement with the estimated mean steady state NOP (9.2 ± 9.3 mmol O2 m−2 d−1 compared to 11.7 ± 1.1 mmol O2 m−2 d−1, respectively).
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Metabolic Balance in the mixed layer of the oligotrophic North Pacific Ocean from diel changes in O2/Ar saturation ratios
Geophysical Research Letters, 2015Co-Authors: Sara Ferron, Samuel T Wilson, Paul D Quay, Sandra Martínez-garcía, David M KarlAbstract:In situ measurements were made to determine oxygen (O2) Metabolic Balance in the upper oligotrophic ocean from diel changes in O2 to argon (Ar) ratios. The study took place during 13–24 March 2014, at the Hawaii Ocean Time-series Station ALOHA (A Long-term Oligotrophic Habitat Assessment), in the North Pacific Subtropical Gyre. Microbial community respiration and gross O2 production, estimated from in situ diel changes in O2/Ar saturation, agreed well with those calculated using other independent methods. Net oxygen production (NOP), estimated from in situ diel changes in O2/Ar saturation, showed large day-to-day variability. However, when averaged over the entire observational period, mean diel NOP was in relatively good agreement with the estimated mean steady state NOP (9.2 ± 9.3 mmol O2 m−2 d−1 compared to 11.7 ± 1.1 mmol O2 m−2 d−1, respectively).
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net community production and Metabolic Balance at the oligotrophic ocean site station aloha
Deep Sea Research Part I: Oceanographic Research Papers, 2004Co-Authors: Peter Le J B Williams, Paul J. Morris, David M KarlAbstract:Abstract To test the hypothesis that in oligotrophic areas of the ocean respiration exceeds production, a 12-month study was undertaken of in vitro-determined net oxygen production and consumption in the top 150 m of the water column at the extreme oligotrophic site, Station ALOHA, in the North Pacific subtropical gyre. Throughout the year the water column was observed to be in Metabolic deficit, the calculated cumulative shortfall being 9±1.7 mol O 2 m −2 a −1 (approximately 100 g C m −2 a −1 ), an amount equivalent to 40% of measured production (annual estimated rates of production and consumption were, respectively, 22 and 31 mol O 2 m −2 a −1 ). We consider three possible explanations for the observed deficit: (1) the in vitro oxygen rate measurements, in themselves, are fundamentally flawed and should be discounted, (2) the observations are correct and the observed deficit is a true account of the Balance of oxygen (and organic carbon) at Station ALOHA, or (3) the observations are correct as they stand, but need not be interpreted as organic carbon imBalance for that ecosystem. We find no error unique to the oxygen rate measurements themselves. We find also no evidence that the associated organic carbon deficit can be sustained over the long-term by internal organic reserves or by external subsidy. Accordingly we accept the geochemical findings that calculated in situ oxygen flux requires the euphotic zone of the water column at this site to be slightly (circa 2 mol C m −2 a −1 ) autotrophic, in contrast to the simple analysis of our observations which gives a net heterotrophic water column. We discuss a number of processes that may give rise to the observed discrepancy. In part it may derive from the difficulty of reproducing the variations in the light field experienced by an algal cell due to vertical advection. It may also derive from the intermittency of production. This latter effect would manifest itself in the following manner. Because of its universal distribution in the food web, respiration has greater integrating properties than photosynthesis and so will give a more accurate estimate of the long-term mean in studies with coarse sampling frequencies. If the system is undersampled, then short bursts of photosynthesis are prone to be missed from the integration of the production term but will be seen in the consumption term: hence the apparent deficit. The corollary of this line of reasoning is that, in undersampled systems, respiration has the potential to give a more accurate measurement of integrated system production than photosynthesis.
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Metabolic Balance of the open sea
Nature, 2003Co-Authors: David M Karl, Edward A Laws, Paul Morris, Peter Le J B Williams, Steven EmersonAbstract:The rise of oxygenic photosynthesis nearly three billion years ago led to the accumulation of free oxygen and to the subsequent diversification of life on Earth; today, nearly half of all oxygen production derives from the photosynthetic activities of marine phytoplankton1. The conclusion that the open sea –– and therefore much of our planet's surface –– is in a net heterotrophic Metabolic state2, 3, 4 is enigmatic and is a first-order question in the global carbon cycle, as discussed by del Giorgio and Duarte5. Our findings suggest that autotrophy in the open sea is episodic and decoupled from the more constant heterotrophic processes. Consequently, the Metabolic Balance of the open sea depends on proper space and timescale integration to achieve an ecological understanding of life in the sea.
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Global carbon cycle (communication arising): Metabolic Balance of the open sea
Nature, 2003Co-Authors: David M Karl, Edward A Laws, Paul J. Morris, Peter J. Le B. Williams, Steven EmersonAbstract:The rise of oxygenic photosynthesis nearly three billion years ago led to the accumulation of free oxygen and to the subsequent diversification of life on Earth; today, nearly half of all oxygen production derives from the photosynthetic activities of marine phytoplankton1. The conclusion that the open sea –– and therefore much of our planet's surface –– is in a net heterotrophic Metabolic state2, 3, 4 is enigmatic and is a first-order question in the global carbon cycle, as discussed by del Giorgio and Duarte5. Our findings suggest that autotrophy in the open sea is episodic and decoupled from the more constant heterotrophic processes. Consequently, the Metabolic Balance of the open sea depends on proper space and timescale integration to achieve an ecological understanding of life in the sea.
Palle Jeppesen - One of the best experts on this subject based on the ideXlab platform.
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Repeated Metabolic Balance Studies in Patients With Short Bowel Syndrome
Journal of Parenteral and Enteral Nutrition, 2019Co-Authors: Johanna Eliasson, Kristian A. Fuglsang, Mark Hvistendahl, Rahim M Naimi, Palle JeppesenAbstract:Weaning from parenteral support is considered indirect evidence of intestinal adaptation in patients with short bowel syndrome (SBS), but direct evidence is lacking. The objective of this study was to examine if intestinal adaptation could be demonstrated as increase in intestinal absorption of energy and wet weight over time measured by repeated Metabolic Balance studies (MBSs) and to examine whether adaptation was determined by the anatomy of the remnant bowel. We retrospectively analyzed data from 48 repeated MBSs performed in 13 adult patients with SBS. Results were presented graphically and interpreted. The interpatient and intrapatient heterogeneity was compared based on anatomy of the remnant bowel. The number of repeated MBSs ranged from 2 to 7, and time between last intestinal resection and MBS from 5 months to 18.1 years. In 6 patients, the first MBS was performed within 2 years after last resection, but only 1 patient had repeated MBSs within this period. Nine patients had an end jejunoileostomy, and 4 patients had a jejuno-colonic or ileo-colonic anastomosis. None of the patients had jejunoileal anastomosis with a preserved ileocecal valve. Interpatient and intrapatient heterogeneity of wet weight and energy absorption was larger in patients without colon in continuity. The wet weight and energy absorption data showed no tendency toward intestinal adaptation in any anatomical group. We observed no signs of late-phase intestinal adaptation in this selected group of patients with SBS. Future prospective MBSs are needed to understand the time course and magnitude of intestinal adaptation. © 2019 American Society for Parenteral and Enteral Nutrition.
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Repeated Metabolic Balance Studies in Patients With Short Bowel Syndrome.
Journal of Parenteral and Enteral Nutrition, 2019Co-Authors: Johanna Eliasson, Kristian A. Fuglsang, Mark Hvistendahl, Rahim M Naimi, Palle JeppesenAbstract:BACKGROUND: Weaning from parenteral support is considered indirect evidence of intestinal adaptation in patients with short bowel syndrome (SBS), but direct evidence is lacking. The objective of this study was to examine if intestinal adaptation could be demonstrated as increase in intestinal absorption of energy and wet weight over time measured by repeated Metabolic Balance studies (MBSs) and to examine whether adaptation was determined by the anatomy of the remnant bowel. METHODS: We retrospectively analyzed data from 48 repeated MBSs performed in 13 adult patients with SBS. Results were presented graphically and interpreted. The interpatient and intrapatient heterogeneity was compared based on anatomy of the remnant bowel. RESULTS: The number of repeated MBSs ranged from 2 to 7, and time between last intestinal resection and MBS from 5 months to 18.1 years. In 6 patients, the first MBS was performed within 2 years after last resection, but only 1 patient had repeated MBSs within this period. Nine patients had an end jejunoileostomy, and 4 patients had a jejuno-colonic or ileo-colonic anastomosis. None of the patients had jejunoileal anastomosis with a preserved ileocecal valve. Interpatient and intrapatient heterogeneity of wet weight and energy absorption was larger in patients without colon in continuity. The wet weight and energy absorption data showed no tendency toward intestinal adaptation in any anatomical group. CONCLUSION: We observed no signs of late-phase intestinal adaptation in this selected group of patients with SBS. Future prospective MBSs are needed to understand the time course and magnitude of intestinal adaptation.
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Fasting and Postprandial Plasma Citrulline and the Correlation to Intestinal Function Evaluated by 72-Hour Metabolic Balance Studies in Short Bowel Jejunostomy Patients With Intestinal Failure.
Journal of Parenteral and Enteral Nutrition, 2017Co-Authors: Hilde Fjermestad, Mark Hvistendahl, Palle JeppesenAbstract:BACKGROUND: Fasting plasma citrulline (p-citrulline) is a marker of functional enterocyte mass. However, the optimal timing of measurement in relation to meals has yet to be clarified. Furthermore, p-citrulline has been proposed to be a surrogate marker for small bowel length and intestinal absorption parameters in short bowel syndrome patients with intestinal failure (SBS-IF). MATERIALS AND METHODS: Eight patients with SBS-IF and 8 healthy controls (HCs) were given a standardized mixed test meal, and p-citrulline was measured 15 minutes before and 60, 120, and 180 minutes after completion of the meal. The patients with SBS-IF had their intestinal absorption of wet weight, energy, macronutrients, and electrolytes measured in relation to 72-hour Metabolic Balance studies. We investigated the possible correlations between p-citrulline and short bowel length, absorptive parameters, and the dependence on parenteral support (PS). RESULTS: In the patients with SBS-IF, we found a 12% (P = .041) reduction in postprandial citrulline levels after 180 minutes. In the HCs, there was a 13% postprandial reduction at 60 minutes (P = .018). No significant correlations between fasting p-citrulline and bowel length, bowel absorptive function, or the dependence on PS were found. Even when excluding 2 patients in whom the intestinal absorption was adjacent to the intestinal insufficiency borderlines, these correlations were not significant. CONCLUSION: Based on findings in this small study, the optimal timing of p-citrulline measurement is on fasting samples. However, p-citrulline seems insufficiently discriminative to serve as a valid biomarker of bowel length, bowel absorptive function, or dependence on PS in patients with SBS-IF.
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The use of Metabolic Balance studies in the objective discrimination between intestinal insufficiency and intestinal failure.
The American Journal of Clinical Nutrition, 2017Co-Authors: August P. Prahm, Christopher F. Brandt, C. Askov-hansen, Per Brøbech Mortensen, Palle JeppesenAbstract:: Background: In research settings that use Metabolic Balance studies (MBSs) of stable adult patients with short bowel syndrome, intestinal failure (IF) and dependence on parenteral support (PS) have been defined objectively as energy absorption
Matthew D Hirschey - One of the best experts on this subject based on the ideXlab platform.
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sirt3 weighs heavily in the Metabolic Balance a new role for sirt3 in Metabolic syndrome
Journals of Gerontology Series A-biological Sciences and Medical Sciences, 2013Co-Authors: Michelle F Green, Matthew D HirscheyAbstract:: Eating a "Western diet" high in fat and sugars is associated with accelerated development of age-related Metabolic diseases such as obesity, insulin resistance, and diabetes while incidences of these diseases are decreased on a low-calorie diet. The mitochondrial NAD(+)-dependent protein deacetylase SIRT3 has previously been shown to be important in adapting to Metabolic stress brought on by fasting and calorie restriction. During times of Metabolic stress, SIRT3 is upregulated and maintains homeostasis following nutrient deprivation by turning on pathways such as fatty acid oxidation, antioxidant production, and the urea cycle. New studies now demonstrate that SIRT3 is regulated during nutrient excess. During high-fat diet feeding, SIRT3 is downregulated leading to mitochondrial protein hyperacetylation. The consequence of this hyperacetylation is the accelerated development of Metabolic syndrome. Thus, SIRT3 is emerging as an important Metabolic sensor working to restore Metabolic homeostasis during times of stress.
Jose M Montoya - One of the best experts on this subject based on the ideXlab platform.
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warming alters the Metabolic Balance of ecosystems
Philosophical Transactions of the Royal Society B, 2010Co-Authors: Gabriel Yvondurocher, Iwan J Jones, Mark Trimmer, Guy Woodward, Jose M MontoyaAbstract:The carbon cycle modulates climate change, via the regulation of atmospheric CO2, and it represents one of the most important services provided by ecosystems. However, considerable uncertainties remain concerning potential feedback between the biota and the climate. In particular, it is unclear how global warming will affect the Metabolic Balance between the photosynthetic fixation and respiratory release of CO2 at the ecosystem scale. Here, we present a combination of experimental field data from freshwater mesocosms, and theoretical predictions derived from the Metabolic theory of ecology to investigate whether warming will alter the capacity of ecosystems to absorb CO2. Our manipulative experiment simulated the temperature increases predicted for the end of the century and revealed that ecosystem respiration increased at a faster rate than primary production, reducing carbon sequestration by 13 per cent. These results confirmed our theoretical predictions based on the differential activation energies of these two processes. Using only the activation energies for whole ecosystem photosynthesis and respiration we provide a theoretical prediction that accurately quantified the precise magnitude of the reduction in carbon sequestration observed experimentally. We suggest the combination of whole-ecosystem manipulative experiments and ecological theory is one of the most promising and fruitful research areas to predict the impacts of climate change on key ecosystem services.
Nikolai Friberg - One of the best experts on this subject based on the ideXlab platform.
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temperature and the Metabolic Balance of streams
Freshwater Biology, 2011Co-Authors: Benoit O L Demars, Guy Woodward, Russell J Manson, Jon S Olafsson, Gisli Mar Gislason, Rakel Gudmundsdottir, Julia Reiss, Doris E Pichler, Jes J Rasmussen, Nikolai FribergAbstract:Summary 1. It is becoming increasingly clear that fresh waters play a major role in the global C cycle. Stream ecosystem respiration (ER) and gross primary productivity (GPP) exert a significant control on organic carbon fluxes in fluvial networks. However, little is known about how climate change will influence these fluxes. 2. Here, we used a ‘natural experiment’ to demonstrate the role of temperature and nutrient cycling in whole-system metabolism (ER, GPP and net ecosystem production – NEP), in naturally heated geothermal (5–25 °C) Icelandic streams. 3. We calculated ER and GPP with a new, more accurate method, which enabled us to take into account the additional uncertainties owing to stream spatial heterogeneity in oxygen concentrations within a reach. ER ranged 1–25 g C m−2 day−1 and GPP 1–10 g C m−2 day−1. The median uncertainties (based on 1 SD) in ER and GPP were 50% and 20%, respectively. 4. Despite extremely low water nutrient concentrations, high Metabolic rates in the warm streams were supported by fast cycling rates of nutrients, as revealed from inorganic nutrient (N, P) addition experiments. 5. ER exceeded GPP in all streams (with average GPP/ER = 0.6) and was more strongly related to temperature than GPP, resulting in elevated negative NEP with warming. We show that, as a first approximation based on summer investigations, global stream carbon emission to the atmosphere would nearly double from 0.12 Pg C year−1 at 13 °C to 0.21 (0.15–0.33) Pg C year−1 with a 5 °C warming. 6. Compared to previous studies from natural systems (including terrestrial ecosystems), the temperature dependence of stream metabolism was not confounded by latitude or altitude, seasonality, light and nutrient availability, water chemistry, space availability (water transient storage), and water availability. 7. Consequently, stream nutrient processing is likely to increase with warming, protecting downstream ecosystems (rivers, estuaries, coastal marine systems) during the summer low flows from nutrient enrichment, but at the cost of increased CO2 flux back to the atmosphere.