Glucocorticoids Decrease the Conversion of Thyroxine into 3,5,3′-Tri-Iodothyronine by Isolated Rat Renal Tubules

1982 ◽  
Vol 62 (2) ◽  
pp. 215-220 ◽  
Author(s):  
P. Heyma ◽  
R. G. Larkins
Keyword(s):  
Strong Evidence ◽  
Glucocorticoid Receptors ◽  
Actinomycin D ◽  
Time Dependent ◽  
Renal Tubules ◽  
Short Term ◽  
Collagenase Digestion ◽  
Isolated Rat

1. The effect of glucocorticoids on the deiodination of thyroxine (T4) to 3,5,3′-tri-iodothyronine (T3) was studied in rat renal tubules prepared by collagenase digestion. 2. In short-term (6 h) experiments, cortisol and dexamethasone inhibited the conversion of T4 into T3 at concentrations of 2 × 10-4 mol/l and 2 × 10-5 mol/l respectively. The inhibition by cortisol and dexamethasone was time dependent and was prevented by actinomycin D and progesterone, suggesting that the inhibition is mediated by an effect on nuclear transcription dependent on binding to glucocorticoid receptors. 3. In long-term (16 h) experiments, cortisol and dexamethasone inhibited T4 to T3 conversion by the tubules at concentrations of 1 × 10-12 mol/l and above. In addition, physiological concentrations of corticosterone (1 × 10-8 mol/l) were able to decrease T3 generation from T4. 4. Our data provide strong evidence that physiological concentrations of glucocorticoids are able to affect T3 production from T4 directly and suggest that they may be important regulators of T4 deiodination.

Selected Contribution: Chronic intermittent hypoxia enhances respiratory long-term facilitation in geriatric female rats

2003 ◽  
Vol 95 (6) ◽  
pp. 2614-2623 ◽  
Author(s):  
A. G. Zabka ◽  
G. S. Mitchell ◽  
E. B. Olson ◽  
M. Behan
Keyword(s):  
Intermittent Hypoxia ◽  
Young Female ◽  
Time Dependent ◽  
Female Rats ◽  
Chronic Intermittent Hypoxia ◽  
Middle Aged ◽  
Short Term ◽  
Hypoxic Response ◽  
Long Term Facilitation

Age and the estrus cycle affect time-dependent respiratory responses to episodic hypoxia in female rats. Respiratory long-term facilitation (LTF) is enhanced in middle-aged vs. young female rats ( 72 ). We tested the hypothesis that phrenic and hypoglossal (XII) LTF are diminished in acyclic geriatric rats when fluctuating sex hormone levels no longer establish conditions that enhance LTF. Chronic intermittent hypoxia (CIH) enhances LTF ( 41 ); thus we further predicted that CIH would restore LTF in geriatric female rats. LTF was measured in young (3-4 mo) and geriatric (20-22 mo) female Sasco Sprague-Dawley rats and in a group of geriatric rats exposed to 1 wk of nocturnal CIH (11 vs. 21% O2 at 5-min intervals, 12 h/night). In anesthetized, paralyzed, vagotomized, and ventilated rats, time-dependent hypoxic phrenic and XII responses were assessed. The short-term hypoxic response was measured during the first of three 5-min episodes of isocapnic hypoxia (arterial Po2 35-45 Torr). LTF was assessed 15, 30, and 60 min postepisodic hypoxia. Phrenic and XII short-term hypoxic response was not different among groups, regardless of CIH treatment ( P > 0.05). LTF in geriatric female rats was smaller than previously reported for middle-aged rats but comparable to that in young female rats. CIH augmented phrenic and XII LTF to levels similar to those of middle-aged female rats without CIH ( P < 0.05). The magnitude of phrenic and XII LTF in all groups was inversely related to the ratio of progesterone to estradiol serum levels ( P < 0.05). Thus CIH and sex hormones influence the magnitude of LTF in geriatric female rats.

Seasonal to multi-annual speedup and slowdown of Greenland outlet glaciers inferred from time-dependent remote sensing observations

2020 ◽  
Author(s):  
Lizz Ultee ◽  
Bryan Riel ◽  
Brent Minchew
Keyword(s):  
Time Series ◽  
Flow Velocity ◽  
Ice Sheet ◽  
Surface Air Temperature ◽  
Greenland Ice Sheet ◽  
Time Dependent ◽  
Surface Velocity ◽  
Short Term ◽  
Ice Flow

&lt;p&gt;The rate of ice flux from the Greenland Ice Sheet to the ocean depends on the ice flow velocity through outlet glaciers. Ice flow velocity, in turn, evolves in response to multiple geographic and environmental forcings at different timescales. For example, velocity may vary daily in response to ocean tides, seasonally in response to surface air temperature, and multi-annually in response to long-term trends in climate. The satellite observations processed as part of the NASA MEaSUREs Greenland Ice Sheet Velocity Map allow us to analyse variations in ice surface velocity at multiple timescales. Here, we decompose short-term and long-term signals in time-dependent velocity fields for Greenland outlet glaciers based on the methods of Riel et al. (2018). Patterns found in short-term signals can constrain basal sliding relations and ice rheology, while the longer-term signals hint at decadal in/stability of outlet glaciers. We present example velocity time series for outlets including Sermeq Kujalleq (Jakobshavn Isbrae) and Helheim Glacier, and we highlight features indicative of dynamic drawdown or advective restabilization. Finally, we comment on the capabilities of a time series analysis software under development for glaciological applications.&lt;/p&gt;

The Formation of Tri-Iodothyronine and Reverse Triiodothyronine from Thyroxine in Isolated Rat Renal Tubules

1978 ◽  
Vol 55 (6) ◽  
pp. 567-572
Author(s):  
P. Heyma ◽  
R. G. Larkins ◽  
J. R. Stockigt ◽  
D. G. Campbell
Keyword(s):  
Therapeutic Range ◽  
Inhibitory Effect ◽  
Renal Tubules ◽  
Intact Cells ◽  
Reverse Triiodothyronine ◽  
Collagenase Digestion ◽  
Subsequent Degradation ◽  
Isolated Rat

1. Conversion of thyroxine into triiodothyronine and reverse tri-iodothyronine in intact cells was studied with isolated renal tubules prepared by collagenase digestion. 2. Conversion of thyroxine into triiodothyronine and reverse tri-iodothyronine increased progressively for at least 90 min. 3. Studies of tri-iodothyronine production from increasing amounts of thyroxine revealed that the thyroxine to tri-iodothyronine conversion is saturable. 4. Iodide and carbimazole had no effect on the thyroxine to tri-iodothyronine conversion. 5. 6-Propyl-2-thiouracil had a direct noncompetitive inhibitory effect on the conversion of thyroxine into tri-iodothyronine with a 75% inhibition of the conversion at a propylthiouracil concentration within the therapeutic range in vivo. Propylthiouracil also inhibited the net formation of reverse tri-iodothyronine from thyroxine at a similar propylthiouracil concentration, as well as inhibiting the subsequent degradation of reverse triiodothyronine.

Association of adrenal hormone metabolites and mortality over a 6-year follow-up in COPD patients with acute exacerbation

2018 ◽  
Vol 56 (4) ◽  
pp. 669-680 ◽  
Author(s):  
Seline Zurfluh ◽  
Manuela Nickler ◽  
Manuel Ottiger ◽  
Christian Steuer ◽  
Alexander Kutz ◽  
...  
Keyword(s):  
Cox Regression ◽  
Time Dependent ◽  
Chronic Obstructive ◽  
Short Term ◽  
Therapeutic Implications ◽  
Adrenal Hormone ◽  
Copd Patients ◽  
Short And Long Term ◽  
Long Term Mortality

Abstract Background: The release of hormones from the adrenal gland is vital in acute and chronic illnesses such as chronic obstructive pulmonary disease (COPD) involving recurrent exacerbations. Using a metabolomic approach, we aim to investigate associations of different adrenal hormone metabolites with short- and long-term mortality in COPD patients. Methods: We prospectively followed 172 COPD patients (median age 75 years, 62% male) from a previous Swiss multicenter trial. At baseline, we measured levels of a comprehensive spectrum of adrenal hormone metabolites, including glucocorticoid, mineralocorticoid and androgen hormones by liquid chromatography coupled with tandem mass spectrometry (MS). We calculated Cox regression models adjusted for gender, age, comorbidities and previous corticosteroid therapy. Results: Mortality was 6.4% after 30 days and increased to 61.6% after 6 years. Higher initial androgen hormones predicted lower long-term mortality with significant results for dehydroepiandrosterone (DHEA) [adjusted hazard ratio (HR), 0.82; 95% confidence interval (CI), 0.70–0.98; p=0.026] and dehydroepiandrosterone sulfate (DHEA-S) (adjusted HR, 0.68; 95% CI, 0.50–0.91; p=0.009). An activation of stress hormones (particularly cortisol and cortisone) showed a time-dependent effect with higher levels pointing towards higher mortality at short term, but lower mortality at long term. Activation of the mineralocorticoid axis tended to be associated with increased short-term mortality (adjusted HR of aldosterone, 2.76; 95% CI, 0.79–9.65; p=0.111). Conclusions: Independent of age, gender, corticosteroid exposure and exacerbation type, adrenal hormones are associated with mortality at short and long term in patients with COPD exacerbation with different time-dependent effects of glucocorticoids, androgens and mineralocorticoids. A better physiopathological understanding of the causality of these effects may have therapeutic implications.

scholarly journals EARTHQUAKE FORECAST BY TIME-DEPENDENT HAZARD MODELS

2017 ◽  
Vol 50 (3) ◽  
pp. 1309
Author(s):  
R. Console
Keyword(s):  
Epidemic Model ◽  
Stress Change ◽  
Time Dependent ◽  
Occurrence Rate ◽  
Hazard Models ◽  
Short Term ◽  
Probability Of Occurrence ◽  
Seismogenic Structures ◽  
Definition Of

This presentation outlines methodological aspects of earthquake forecasting. The recurring debates concerning predictability of earthquakes clearly show how this problem is centred on the difficulty of systematically testing the numerous methodologies that in the years have been proposed and sustained by the supporters of prediction. This difficulty starts, sometimes, from the lack of a quantitative and rigorous definition of the concerned precursor, and other times from the lack of continuous observations, upon which statistical analyses could be based. After an introduction concerning the definition of earthquake precursors, the way how to validate forecast hypotheses and the cost associated to their operational application, I give two examples of time-dependent hazard models, for long-term and short-term earthquake forecasts respectively. Considering the long-term forecast modelling, the effect of stress change due to previous historical earthquakes on the probability of occurrence of future earthquakes on neighbouring faults is taken into account. Following a standard methodology developed a couple of decades ago, the probability of occurrence in the next 50 years for a characteristic earthquake on known seismogenic structures can be estimated by a time-dependent renewal model. Then, a physical model for the Coulomb stress change caused by previous earthquakes on these structures is applied. The influence of this stress change on the occurrence rate of characteristic earthquakes is computed taking into account the permanent perturbation (clock advance). The method so developed is applied to the computation of earthquake hazard of the main seismogenic structures recognized in the Southern Apennines region, for which both historical and paleoseismological data are available. A popular short-term time dependent hazard forecast model is the epidemic model. In this model earthquakes are regarded as the realization of a stochastic point process, and their magnitude distribution is described by the Gutenberg-Richter law with a constant b-value. The occurrence rate density is computed by the sum of two terms, one representing the independent, or spontaneous activity, and the other representing the activity induced by previous earthquakes. While the first term depends only on space, the second one is factored into three terms that respectively include the magnitude, time and location of the past earthquakes. An example of application of the epidemic model to the 2009 L’Aquila seismic series is shown.

Splenectomy in Patients with Myeloproliferative Neoplasms (MPNs): Efficacy, Complications and Impact On Survival and Transformation.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2853-2853
Author(s):  
Fabio P S Santos ◽  
Constantine S. Tam ◽  
Hagop M. Kantarjian ◽  
Jorge E. Cortes ◽  
Deborah A. Thomas ◽  
...  
Keyword(s):  
Myeloproliferative Neoplasms ◽  
Therapeutic Option ◽  
Splenic Vein ◽  
Time Dependent ◽  
Chromosome 17 ◽  
Short Term ◽  
Post Surgery ◽  
Impact On Survival ◽  
Md Anderson

Abstract Abstract 2853 Introduction: Splenectomy may be an effective therapeutic option for treating massive splenomegaly in patients with MPNs. There is still limited data on its short- and long-term benefits and risks. Objective: To describe short-term outcomes, complications and impact on survival and transformation to acute myeloid leukemia (AML) in patients with MPNs who underwent splenectomy. Methods: First, efficacy and short-term complications were analyzed in 94 patients with different MPNs who underwent splenectomy at MD Anderson between 1981–2009. Second, medical records of 696 patients with myelofibrosis (MF) seen at MD Anderson between 1966–2009 were reviewed (among which 91 underwent splenectomy either at or outside MD Anderson) to evaluate the long-term impact of splenectomy on overall survival (OS) and transformation-free survival (TFS). Improvement in anemia and thrombocytopenia were defined by the International Working Group on Myelofibrosis Research and Treatment response criteria. Survival was estimated by Kaplan-Meier method, and hazard ratios (HR) were determined by Cox multivariate analysis. Splenectomy was analyzed as a time-dependent covariate. Risk in patients with MF was determined by the Dynamic International Prognostic Scoring System (DIPSS). Accelerated phase (AP) criteria in MF were determined as thrombocytopenia <50×109/L, chromosome 17 abnormalities and blasts >10% in peripheral blood (PB) or bone marrow (BM). Results: Splenectomy improved spleen pain, anemia and thrombocytopenia in 84%, 47% and 66% of patients, respectively. Among patients with MF, improvement in anemia and thrombocytopenia was seen in 44% and 75% of patients, respectively. Hematological complications included post-operative leukocytosis (76%) and thrombocytosis (43%), developing within a median time of 1 day and 5 days post-surgery, respectively. Early (<7 days) intervention for control of elevated white blood cell and/or platelet count was needed in 37% of patients. Forty-six percent of patients developed non-hematological clinical complications, and the most common was venous thromboembolism (VTE; 16%). VTE sites included portal vein (N=11), supra-hepatic vein (N=3) and superior vena cava, pulmonary embolism and splenic vein (N=1 each). Post-operative mortality was 5%. Median survival post-splenectomy was 19.2 months, and 5-year survival 16.1%. In the second cohort of patients with MF, requirement for splenectomy was associated with decreased OS (HR=2.84, p<0.0001) and TFS (HR=2.79, p<0.0001). In the multivariable model, the time dependent covariate splenectomyremained an independent risk factor for inferior OS and TFS in patients with MF, alongside male sex, transfusion dependency, DIPSS score and AP criteria (Table). Conclusions: Splenectomyis a possible therapeutic option for patients with MF and other MPNs, and its greatest benefits are related to improvement in spleen pain and discomfort, anemia and thrombocytopenia. However, in patients with MF it appears to be associated with increased mortality and risk of transformation to AML. Disclosures: No relevant conflicts of interest to declare.

Prediction of organic matter degradability in river sediments

2020 ◽  
Author(s):  
Julia Gebert ◽  
Florian Zander
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Spatial Variability ◽  
River Sediments ◽  
Redox Conditions ◽  
Time Dependent ◽  
Anaerobic Conditions ◽  
Short Term ◽  
Aerobic And Anaerobic

&lt;p&gt;Under anaerobic conditions, degradation of organic matter in river sediments leads to gas formation, with organic carbon being released mainly as CH&lt;sub&gt;4&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt;. Gas bubbles reduce sediment density, viscosity and shear strength, impede sonic depth finding and are suspected to affect the sediments&amp;#8217; rheological properties. Moreover, methane (CH&lt;sub&gt;4&lt;/sub&gt;) is a potent greenhouse gas with a global warming potential (GWP&lt;sub&gt;100&lt;/sub&gt;) of 28-36. Therefore, the climate impact may vary greatly depending on the way sediments are managed (for example, type and frequency of dredging and relocation in the water body or treatment on land). The objective of this paper is therefore to quantify the time-dependent stability, or inversely, the lability of sediment organic matter (SOM) as a basis for prediction of effects on sediment mechanical properties and on the release of greenhouse gases.&lt;/p&gt;&lt;p&gt;Within two years, over 200 samples of predominantly fine-grained sediment were collected from nine locations within a 30 km transect through the Port of Hamburg. All samples were, amongst other analyses, subjected to long-term (&gt; 250 days) aerobic and anaerobic incubation for measurement of SOM degradation, yielding a comprehensive data set on the time-dependent change in degradation rates and the corresponding size of differently degradable SOM pools. SOM degradability exhibited a pronounced spatial variability with an approximately tenfold higher anaerobic and a roughly fivefold higher aerobic degradability of upstream SOM compared to downstream SOM. Lower &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C values, higher DNA concentrations and a higher share of organic carbon in the light density fraction as well as elevated chlorophyll concentrations in the water phase support the hypothesis of increased biological sources of SOM at upstream locations and increased SOM degradability in shallow compared to deep layers (Zander et al., 2020).&lt;/p&gt;&lt;p&gt;First statistical and time series analyses indicate that&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Long-term SOM lability appears to be predictable from short-term measurements.&lt;/li&gt; &lt;li&gt;The relationship between short-term and long-term SOM degradation is site-specific and also differs for layers of different age (depth). This supports the above-mentioned variability between sites regarding the size of differently degradable carbon pools, as well as for the depth profile at any one site.&lt;/li&gt; &lt;li&gt;The relevance of the available electron acceptors (redox conditions) for SOM degradation, i.e. the ratio between carbon release under aerobic and anaerobic conditions, differs less by site but more so by layers of different age (depth). This is plausible as especially the top layers are exposed to more variability in redox conditions than the deeper layers that are always under reducing conditions.&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;Zander, F., Heimovaara, T., Gebert, J. (2020): Spatial variability of organic matter degradability in tidal Elbe sediments. Journal of Soils and Sediments, accepted for publication.&lt;/p&gt;

scholarly journals Simulations on the survivability of Tidal Dwarf Galaxies

2014 ◽  
Vol 10 (S309) ◽  
pp. 157-158
Author(s):  
Sylvia Ploeckinger ◽  
Simone Recchi ◽  
Gerhard Hensler ◽  
Pavel Kroupa
Keyword(s):  
Dark Matter ◽  
Numerical Simulations ◽  
Dwarf Galaxies ◽  
Time Dependent ◽  
Short Term ◽  
Stellar Feedback ◽  
Term Evolution ◽  
Matter Component ◽  
Simulation Time

AbstractWe present detailed numerical simulations of the evolution of Tidal Dwarf Galaxies (TDGs) after they kinematically decouple from the rest of the tidal arm to investigate their survivability. Both the short-term (500 Myr) response of TDGs to the stellar feedback of different underlying stellar populations as well as the long-term evolution that is dominated by a time dependent tidal field is examined. All simulated TDGs survive until the end of the simulation time of up to 3 Gyr, despite their lack of a stabilising dark matter component.

scholarly journals Time-dependent probabilistic seismic hazard assessment and its application to Hualien City, Taiwan

2013 ◽  
Vol 13 (5) ◽  
pp. 1143-1158 ◽  
Author(s):  
C.-H. Chan ◽  
Y.-M. Wu ◽  
C.-T. Cheng ◽  
P.-S. Lin ◽  
Y.-C. Wu
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
Seismic Hazards ◽  
Time Dependent ◽  
Probabilistic Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard ◽  
Short Term ◽  
Seismicity Rate

Abstract. Here, we propose a time-dependent probabilistic seismic hazard assessment and apply it to Hualien City, Taiwan. A declustering catalog from 1940 to 2005 was used to build up a long-term seismicity rate model using a smoothing Kernel function. We also evaluated short-term seismicity rate perturbations according to the rate-and-state friction model, and the Coulomb stress changes imparted by earthquakes from 2006 to 2010. We assessed both long-term and short-term probabilistic seismic hazards by considering ground motion prediction equations for crustal and subduction earthquakes. The long-term seismic hazard in Hualien City gave a PGA (peak ground acceleration) of 0.46 g for the 2.1‰ annual exceedance probability. The result is similar to the levels determined in previous studies. Seismic hazards were significantly elevated following the 2007 ML =5.8 earthquake that occurred approximately 10 km from Hualien City. This work presents an assessment of a suitable mechanism for time-dependent probabilistic seismic hazard determinations using an updated earthquake catalog. Using minor model assumptions, our approach provides a suitable basis for rapid re-evaluations and will benefit decision-makers and public officials regarding seismic hazard mitigation.

Sign in / Sign up

Export Citation Format

Share Document