Regulated hypothermia in the hypothyroid rat induced by administration of propylthiouracil

1997 ◽  
Vol 272 (5) ◽  
pp. R1390-R1395 ◽  
Author(s):  
Y. Yang ◽  
C. J. Gordon
Keyword(s):  
Drinking Water ◽  
Heat Stress ◽  
Temperature Gradient ◽  
Serum Levels ◽  
Male Rats ◽  
Light Phase ◽  
Grooming Behavior ◽  
Ambient Temperatures ◽  
Wide Range ◽  
The Stability

Propylthiouracil (PTU), an antithyroidal drug that reduces serum L-thyroxine (T4) and 3,5,3'-triiodothyronine (T3), is presumed to lower core temperature (T0) by impairing metabolic thermogenesis. However, it is not understood why PTU-treated animals cannot use behavioral and other thermoeffectors to maintain normal Tc. Male rats were administered PTU in drinking water (0.05 mg/ml) while the following parameters were measured: 1) Tc and motor activity (MA) recorded by radiotelemetry for 24 h at ambient temperatures (Ta) of 10-30 degrees C; 2) selected Ta, MA, and Tc in a temperature gradient; and 3) Tc, MA, and grooming behavior during exposure to heat stress (TH = 34.5 degrees C) for 2 h. PTU reduced serum levels of T4, and T3 by 95 and 60%, respectively. Tc decreased after 3 days of PTU treatment; a 0.5 degree C decrease in Tc persisted throughout the PTU treatment. PTU rats exposed to Ta of 10-30 degrees C maintained a consistent hypothermic Tc during the light phase; however, a deficit in the stability of Tc at night was noted during exposure to 10 degrees C. In the temperature gradient, PTU rats selected warmer Ta, but their Tc was maintained at the same hypothermic levels as observed at fixed Ta values of 15-30 degrees C. Heat stress caused Tc of control rats to increase to 39 degrees C, whereas Tc of the PTU rats was maintained below 38 degrees C. The regulation of Tc at hypothermic levels over a wide range of Ta values and when rats were housed in a temperature gradient indicates that chronic PTU induces a state of regulated hypothermia.

An Accurate and Simple Approach to Allow for the Transient Temperature Gradient in a Vaporizing Droplet

2012 ◽  
Author(s):  
Alexander Snegirev ◽  
Victor Talalov
Keyword(s):  
Temperature Gradient ◽  
Life Time ◽  
Droplet Evaporation ◽  
Transient Temperature ◽  
Internal Temperature ◽  
Ambient Temperatures ◽  
Wide Range ◽  
Order Polynomial ◽  
Volatile Liquid ◽  
Evaporation Dynamics

The purpose of this work is to analyze the importance of considering internal temperature gradient in modeling droplet evaporation, and to demonstrate performance of simplified methods in which the temperature gradient is approximately taken into account. Based on three characteristic time scales, two dimensionless criteria have been identified which determine magnitude of the internal temperature gradient and its effect on the evaporation dynamics. Numerical values of these criteria in a wide range of ambient temperatures show that the effect of the internal temperature gradient is more pronounced in more volatile liquid at higher ambient temperatures. Although droplet life time predictions are not sensitive to the internal temperature gradient, its effect might be strong at the initial stages of droplet evaporation, and this substantiates the need in robust and computationally inexpensive methods to take it into account. Two simple and yet accurate approaches (quasi-steady higher order polynomial approximation and the integral balance method) have been favourably tested and recommended for use in CFD spray modeling.

Emergence of heat stress hazards in the CMIP6 models

2020 ◽  
Author(s):  
Natalie S. Lord ◽  
Dann M. Mitchell
Keyword(s):  
Heat Stress ◽  
Mortality Rates ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Number Of Factors ◽  
Event Attribution ◽  
Wide Range ◽  
Effects Of Temperature ◽  
The Impact ◽  
Extreme Heat Stress

<p>Hazards associated with the combined effects of temperature and humidity can have a wide range of impacts, particularly on human health and agriculture. The human body removes metabolic heat through sweating and heat conduction, and the efficiency of these processes is reduced when ambient temperatures and humidity are high, resulting in heat stress. The effects of this range from general discomfort to increased morbidity and mortality rates, trends that have been observed during recent severe heatwaves such as those that occurred during the summer of 2019 in Europe. A number of factors may exacerbate heat stress, including intense physical activity and being located in an urban area as opposed to a rural area.</p><p>As global temperatures increase, the risk associated with heat stress hazards is expected to increase, and this signal is expected to emerge from natural variability over the coming decades, if not sooner. Here, simulations from the new CMIP6 models are analysed to investigate the timing of emergence of heat stress hazards, in order to identify regions of the globe that are particularly vulnerable to extreme heat stress and/or imminent emergence of these hazards. Event attribution techniques are also applied to estimate the impact of anthropogenic warming on the hazard risk.</p>

Stability of Flow Between Arbitrarily Spaced Concentric Cylindrical Surfaces Including the Effect of a Radial Temperature Gradient

1964 ◽  
Vol 31 (4) ◽  
pp. 585-593 ◽  
Author(s):  
J. Walowit ◽  
S. Tsao ◽  
R. C. DiPrima
Keyword(s):  
Temperature Gradient ◽  
Couette Flow ◽  
Simple Formula ◽  
Negative Temperature ◽  
Radial Temperature Gradient ◽  
Radial Temperature ◽  
Simple Set ◽  
Wide Range ◽  
The Stability ◽  
The Galerkin Method

The stability of Couette flow and flow due to an azimuthal pressure gradient between arbitrarily spaced concentric cylindrical surfaces is investigated. The stability problems are solved by using the Galerkin method in conjunction with a simple set of polynomial expansion functions. Results are given for a wide range of spacings. For Couette flow, in the case that the cylinders rotate in the same direction, a simple formula for predicting the critical speed is derived. The effect of a radial temperature gradient on the stability of Couette flow is also considered. It is found that positive and negative temperature gradients are destabilizing and stabilizing, respectively.

scholarly journals The strategy for dealing with heat stress in poultry

2020 ◽  
pp. 25-28
Author(s):  
N. V. Yavnikov
Keyword(s):  
Drinking Water ◽  
Heat Stress ◽  
Negative Impact ◽  
Economic Losses ◽  
Organic Complex ◽  
Negative Effects ◽  
Summer Period ◽  
Ambient Temperatures ◽  
Poultry Farming

Relevance and methods. In the summer period heat stress becomes one of the most serious problems of industrial poultry farming. At its core heat stress is an imbalance between the flow of heat from the environment and the release of energy by the bird's body. This pathology brings tangible economic losses and can cause a massive mortality of the poultry. The article describes a set of measures to minimize the negative impact of extremely high ambient temperatures on the poultry.Results. To deal with the negative effects of heat stress, it was proposed to lower the pH of drinking water by adding the Complicid’s organic complex of acids, and to increase the concentration of nutrients in the poultry diet it was recommended to carry out medication with Libecrin and Butacyfol.

EPISODIC FLUCTUATIONS IN CONCENTRATIONS OF ANDROGEN IN SERUM OF MALE RATS: POSSIBLE RELATIONSHIP TO SEXUAL BEHAVIOUR

1980 ◽  
Vol 87 (3) ◽  
pp. 463-471 ◽  
Author(s):  
P. SÖDERSTEN ◽  
P. ENEROTH ◽  
P.-H. EKBERG
Keyword(s):  
Sexual Behaviour ◽  
Serum Levels ◽  
Male Rats ◽  
Dark Phase ◽  
Light Phase ◽  
Intact Male ◽  
Light Darkness ◽  
High Concentrations ◽  
Episodic Fluctuations ◽  
Late Part

Serum levels of androgen were higher during the late part of the light phase of the light: darkness (LD) cycle than during the late part of the dark phase during three consecutive days in intact male rats. The serum concentration of androgen in blood samples obtained at hourly intervals from individual male rats fluctuated markedly with occasionally as much as a tenfold difference between the highest and lowest values. Evidence was presented that endogenous pulses in the concentrations of androgen in serum of male rats occur during the late part of the light phase and the early and middle parts of the dark phase of the LD cycle. Induction of sexual behaviour by injections of testosterone in castrated rats depended on the time of injection, and the period of maximum behavioural sensitivity to testosterone coincided with the time of the LD cycle when pulses in androgen levels in serum normally occurred in intact rats. Injection of testosterone produced extremely high concentrations of androgen in serum within 0·5 h of injection but these levels declined rapidly thereafter. Testosterone implants, which produced low levels of androgen that did not vary with the LD cycle, were considerably more potent than testosterone injections in stimulating sexual behaviour in castrated rats.

scholarly journals Comparison of heat and cold stress to assess thermoregulatory dysfunction in hypothyroid rats

2000 ◽  
Vol 279 (6) ◽  
pp. R2066-R2071 ◽  
Author(s):  
Christopher J. Gordon ◽  
Peggy Becker ◽  
Beth Padnos
Keyword(s):  
Heat Stress ◽  
Cold Stress ◽  
Serum Levels ◽  
Thyroid Stimulating Hormone ◽  
Overt Hypothyroidism ◽  
Environmental Toxicants ◽  
Thermoregulatory Response ◽  
Light Phase ◽  
Treatment Groups ◽  
Heat And Cold Stress

How borderline impairment of thyroid function can affect thermoregulation is an important issue because of the antithyroidal properties of a many environmental toxicants. This study compared the efficacy of heat and cold stress to identify thermoregulatory deficits in rats subjected to borderline and overt hypothyroidism via subchronic exposure to propylthiouracil (PTU). After 3 wk of exposure to PTU in the drinking water (0, 2.5, 5, 10, and 25 mg/l), rats were subjected to a heat stress challenge (34°C for 2.5 h). After one more week of PTU treatment, the same rats were subjected to a cold stress challenge (7°C for 2.5 h). Core temperature (Tc) was monitored by radiotelemetry. Baseline Tc during the light phase was reduced by treatment with 25 mg/l PTU. The rate of rise and overall increase in Tcduring heat stress was attenuated by PTU doses of 10 and 25 mg/l. Cold stress resulted in a 1.0°C increase in Tc regardless of PTU treatment. The rate of rise in Tc during the cold stress challenge was similar in all PTU treatment groups. There was a dose-related decrease in serum thyroxine (T4) at PTU doses ≥5 mg/l. Serum triiodothyronine (T3) was reduced at PTU doses of 5 and 25 mg/l. Serum thyroid-stimulating hormone (TSH) was marginally elevated by PTU treatment. Overall, heat stress was more effective than cold stress for detecting a thermoregulatory deficit in borderline (i.e., 10 mg/l PTU) and overtly hypothyroid rats (i.e., 25 mg/l PTU). A significant thermoregulatory deficit is manifested with a 78% decrease in serum T4. A thermoregulatory deficit is more correlated with a reduction in serum T4 compared with T3. Serum levels of TSH are unrelated to thermoregulatory response to heat and cold stress.

EFFECT OF BILATERAL CRYPTORCHIDISM UPON PITUITARY AND SERUM LEVELS OF LH AND FSH IN SEXUALLY MATURING MALE RATS

1975 ◽  
Vol 80 (1_Suppla) ◽  
pp. S87
Author(s):  
M. Eichner ◽  
K. Rager ◽  
A. Attanasio ◽  
D. Gupta
Keyword(s):  
Serum Levels ◽  
Male Rats ◽  
Bilateral Cryptorchidism

Effect of Turmeric and Ginger on Lipid Profile in Male Rats Exposed to Oxidative Stress

2019 ◽  
Vol 10 (01) ◽  
Author(s):  
Eman A. Al-Rekabi ◽  
Dheyaa K. Alomer ◽  
Rana Talib Al-Muswie ◽  
Khalid G. Al-Fartosi
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Drinking Water ◽  
Lipid Profile ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Male Rats ◽  
Control Group ◽  
Very Low Density Lipoprotein ◽  
Low Density

The present study aimed to investigate the effect of turmeric and ginger on lipid profile of male rats exposed to oxidative stress induced by hydrogen peroxide H2O2 at a concentration of 1% given with consumed drinking water to male rats. Methods: 200 mg/kg from turmeric and ginger were used, and the animals were treatment for 30 days. Results: the results showed a significant increase in cholesterol, triglycerides, low density lipoprotein (LDL), very low density lipoprotein (VLDL), whereas it explained a significant decrease in high density lipoprotein (HDL) of male rats exposed to oxidative stress when compared with control group. the results showed a significant decrease in cholesterol, triglycerides, (LDL), (VLDL), whereas it explained a significant increase in (HDL) of rats treated with turmeric and ginger at dose 200 mg/kg when compared with male rats exposed to oxidative stress.

Performance of Electronic Structure Methods for the Description of Hückel-Möbius Interconversions in Extended π-Systems

2019 ◽  
Author(s):  
Tatiana Woller ◽  
Ambar Banerjee ◽  
Nitai Sylvetsky ◽  
Xavier Deraet ◽  
Frank De Proft ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Basis Set ◽  
Dft Methods ◽  
Molecular Switching ◽  
Wide Range ◽  
Electronic Structure Methods ◽  
Explicitly Correlated ◽  
Relative Errors ◽  
The Stability ◽  
Basis Set Expansion

<p>Expanded porphyrins provide a versatile route to molecular switching devices due to their ability to shift between several π-conjugation topologies encoding distinct properties. Taking into account its size and huge conformational flexibility, DFT remains the workhorse for modeling such extended macrocycles. Nevertheless, the stability of Hückel and Möbius conformers depends on a complex interplay of different factors, such as hydrogen bonding, p···p stacking, steric effects, ring strain and electron delocalization. As a consequence, the selection of an exchange-correlation functional for describing the energy profile of topological switches is very difficult. For these reasons, we have examined the performance of a variety of wavefunction methods and density functionals for describing the thermochemistry and kinetics of topology interconversions across a wide range of macrocycles. Especially for hexa- and heptaphyrins, the Möbius structures have a pronouncedly stronger degree of static correlation than the Hückel and figure-eight structures, and as a result the relative energies of singly-twisted structures are a challenging test for electronic structure methods. Comparison of limited orbital space full CI calculations with CCSD(T) calculations within the same active spaces shows that post-CCSD(T) correlation contributions to relative energies are very minor. At the same time, relative energies are weakly sensitive to further basis set expansion, as proven by the minor energy differences between MP2/cc-pVDZ and explicitly correlated MP2-F12/cc-pVDZ-F12 calculations. Hence, our CCSD(T) reference values are reasonably well-converged in both 1-particle and n-particle spaces. While conventional MP2 and MP3 yield very poor results, SCS-MP2 and particularly SOS-MP2 and SCS-MP3 agree to better than 1 kcal mol<sup>-1</sup> with the CCSD(T) relative energies. Regarding DFT methods, only M06-2X provides relative errors close to chemical accuracy with a RMSD of 1.2 kcal mol<sup>-1</sup>. While the original DSD-PBEP86 double hybrid performs fairly poorly for these extended p-systems, the errors drop down to 2 kcal mol<sup>-1</sup> for the revised revDSD-PBEP86-NL, again showing that same-spin MP2-like correlation has a detrimental impact on performance like the SOS-MP2 results. </p>

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