Intracerebroventricular physostigmine facilitates heat loss mechanisms in running rats

2004 ◽  
Vol 97 (1) ◽  
pp. 333-338 ◽  
Author(s):  
Alex G. Rodrigues ◽  
Nilo R. V. Lima ◽  
Cândido C. Coimbra ◽  
Umeko Marubayashi
Keyword(s):  
Metabolic Rate ◽  
Heating Rate ◽  
Core Temperature ◽  
Heat Dissipation ◽  
Heat Storage ◽  
Treated Group ◽  
Lower Heat ◽  
Exercise Induced ◽  
Colonic Temperature ◽  
Lateral Cerebral Ventricle

The aim of this study was to evaluate the participation of central cholinergic transmission in the regulation of metabolic rate, core temperature, and heat storage in untrained rats submitted to exercise on a treadmill (20 m/min, 5% inclination) until fatigue. The animals were separated into eight experimental groups, and core temperature or metabolic rate was measured in the rats while they were exercising or while they were at rest after injection of 2 μl of 5 × 10−3 M physostigmine (Phy) or 0.15 M NaCl solution (Sal) into the lateral cerebral ventricle. Metabolic rate was determined by the indirect calorimetry system, and colonic temperature was recorded as an index of core temperature. In resting animals, Phy induced only a small increase in metabolic rate compared with Sal injection, without having any effect on core temperature. During exercise, the Phy-treated animals showed a lower core heating rate (0.022 ± 0.003°C/min Phy vs. 0.033 ± 0.003°C/min Sal; P < 0.02), lower heat storage (285 ± 37 cal Phy vs. 436 ± 34 cal Sal; P < 0.02) and lower core temperature at fatigue point than the Sal-treated group (38.5 ± 0.1°C Phy vs. 39.0 ± 0.1°C Sal; P < 0.05). However, despite the lower core heating rate, heat storage, and core temperature at fatigue, the Phy-treated rats showed a similar running time compared with the Sal-treated group. We conclude that the activation of the central cholinergic system during exercise increases heat dissipation and attenuates the exercise-induced increase in core temperature without affecting running performance.

Effect of hypothyroidism on tolerance of rats to heat

1963 ◽  
Vol 204 (6) ◽  
pp. 1039-1044 ◽  
Author(s):  
Melvin J. Fregly ◽  
Kenneth M. Cook ◽  
Arthur B. Otis
Keyword(s):  
Oxygen Consumption ◽  
Metabolic Rate ◽  
Heat Production ◽  
Heat Exposure ◽  
Muscular Activity ◽  
Heat Conductance ◽  
Lower Heat ◽  
Do Control ◽  
Colonic Temperature ◽  
Skin Temperatures

Hypothyroid (propylthiouracil-treated) rats show slower rates of rise of both colonic and skin temperatures than do control rats when both groups are restrained and exposed to air at 40 C. The increased tolerance to heat does not appear to be associated with increased heat conductance through skin but rather with lower heat production (oxygen consumption). Metabolic rate of hypothyroid rats decreases slightly during heat exposure while that of controls increases. When both groups are compared at the same colonic temperatures during heating, the metabolic rate of hypothyroid rats is significantly less than that of controls. The lower metabolic rate may be a reflection of the lower level of spontaneous muscular activity observed in these animals during heating. The greater tolerance of hypothyroid rats to heat thus appears to be associated with an ability to resist an increase in heat production as colonic temperature rises.

Central angiotensin AT1-receptor blockade affects thermoregulation and running performance in rats

2006 ◽  
Vol 291 (3) ◽  
pp. R603-R607 ◽  
Author(s):  
Laura H. R. Leite ◽  
Ana Cristina R. Lacerda ◽  
Umeko Marubayashi ◽  
Cândido C. Coimbra
Keyword(s):  
Heat Dissipation ◽  
Heat Storage ◽  
Heat Rate ◽  
Receptor Blockade ◽  
Running Performance ◽  
Storage Rate ◽  
Exercise Induced ◽  
The Right ◽  
Body Heat ◽  
Rate Threshold

The effect of central angiotensin AT1-receptor blockade on thermoregulation in rats during exercise on a treadmill (18 m/min, 5% inclination) was investigated. Core (Tb) and skin tail temperatures were measured in rats while they were exercising until fatigue after injection of 2 μl of losartan (Los; 20 nmol, n = 4; 30 nmol, n = 4; 60 nmol, n = 7), an angiotensin II AT1-receptor antagonist, or 2 μl of 0.15 mol/l NaCl (Sal; n = 15) into the right lateral cerebral ventricle. Body heat rate (BHR), heat storage rate, threshold Tb for tail vasodilation (TTbV), time to fatigue, and workload were calculated. During exercise, the BHR and heat storage rate of Los-treated animals were, respectively, 40 and 53% higher ( P < 0.01) than in Sal-treated animals. Additionally, rats injected with Los showed an increased TTbV (38.59 ± 0.19°C for Los vs. 38.12 ± 0.1°C for Sal, P < 0.02), a higher Tb at fatigue point (39.07 ± 0.14°C Los vs. 38.66 ± 0.07°C Sal, P < 0.01), and a reduced running performance (27.29 ± 4.48 min Los vs. 52.47 ± 6.67 min Sal, P < 0.01), which was closely related to the increased BHR. Our data suggest that AT1-receptor blockade attenuates heat dissipation during exercise due to the higher TTbV, leading to a faster exercise-induced increase in Tb, thus decreasing running performance.

Prevention by NCX 4016, a nitric oxide-donating aspirin, but not by aspirin, of the acute endothelial dysfunction induced by exercise in patients with intermittent claudication

2007 ◽  
Vol 97 (03) ◽  
pp. 444-450 ◽  
Author(s):  
Rino Migliacci ◽  
Alessandra Procacci ◽  
Paola De Monte ◽  
Erminio Bonizzoni ◽  
Paolo Gresele
Keyword(s):  
Nitric Oxide ◽  
Endothelial Dysfunction ◽  
Intermittent Claudication ◽  
Treadmill Exercise ◽  
Ischemia Reperfusion ◽  
Treated Group ◽  
Lower Limbs ◽  
Exercise Induced ◽  
Induced Changes ◽  
Ncx 4016

SummaryIschemia/reperfusion damage evokes systemic inflammation and endothelial dysfunction in patients with intermittent claudication. We compared the effects of aspirin with those of a nitric oxide-donating aspirin in preventing the acute, systemic endothelial dysfunction provoked by exercise-induced ischemia of the lower limbs in patients with intermittent claudication. In a prospective, randomized, single-blind, parallel-groups trial among 44 patients with intermittent claudication we compared four weeks of aspirin (100 mg o.d.) with NCX 4016 (800 mg b.i.d.). Primary end point was the exercise-induced changes in brachial flow-mediated vasodilation (FMD) at day 28; secondary end points were effort-induced changes of markers of neutrophil (plasma elastase) and endothelial (soluble VCAM-1) activation. Baseline FMD was comparable in the two groups, both on day I (pre-treatment: aspirin = 3.1 ± 0.5%, nitroaspirin = 3.9 ± 0.7%, p=NS), and on day 28 (aspirin = 3.4 ± 0.7%, NCX 4016 = 3.2 ± 0.6%, p=NS). Maximal treadmill exercise induced an acute worsening of FMD in both groups at baseline (aspirin = –1.15%, nitroaspirin = –1.76%); after four weeks treatment, the impairment of FMD induced by exercise was still present in the aspirin-treated group (- 1.46%) while it was abolished in the NCX 4016-treated group (+ 0.79%, p= 0.038 vs. aspirin). Similarly, exercise induced an increase of plasma elastase and of sVCAM-l which were not affected by aspirin while they were suppressed by NCX 4016. Maximal treadmill exercise induces a systemic arterial endothelial dysfunction in patients with intermittent claudication. A nitric oxide-donating aspirin, but not aspirin, prevents effort-induced endothelial dysfunction.

scholarly journals Approaches for testing hypotheses for the hypometric scaling of aerobic metabolic rate in animals

2018 ◽  
Vol 315 (5) ◽  
pp. R879-R894 ◽  
Author(s):  
Jon F. Harrison
Keyword(s):  
Metabolic Rate ◽  
Heat Loss ◽  
Heat Dissipation ◽  
Morphological Properties ◽  
Compensatory Responses ◽  
Size Dependent ◽  
Extant Species ◽  
Show Evidence ◽  
Selection For ◽  
Interspecific Comparisons

Hypometric scaling of aerobic metabolism [larger organisms have lower mass-specific metabolic rates (MR/g)] is nearly universal for interspecific comparisons among animals, yet we lack an agreed upon explanation for this pattern. If physiological constraints on the function of larger animals occur and limit MR/g, these should be observable as direct constraints on animals of extant species and/or as evolved responses to compensate for the proposed constraint. There is evidence for direct constraints and compensatory responses to O2 supply constraint in skin-breathing animals, but not in vertebrates with gas-exchange organs. The duration of food retention in the gut is longer for larger birds and mammals, consistent with a direct constraint on nutrient uptake across the gut wall, but there is little evidence for evolving compensatory responses to gut transport constraints in larger animals. Larger placental mammals (but not marsupials or birds) show evidence of greater challenges with heat dissipation, but there is little evidence for compensatory adaptations to enhance heat loss in larger endotherms, suggesting that metabolic rate (MR) more generally balances heat loss for thermoregulation in endotherms. Size-dependent patterns in many molecular, physiological, and morphological properties are consistent with size-dependent natural selection, such as stronger selection for neurolocomotor performance and growth rate in smaller animals and stronger selection for safety and longevity in larger animals. Hypometric scaling of MR very likely arises from different mechanisms in different taxa and conditions, consistent with the diversity of scaling slopes for MR.

Myocardial metabolism and coronary flow: effects of endotoxemia

1988 ◽  
Vol 255 (6) ◽  
pp. H1295-H1304 ◽  
Author(s):  
W. L. Rumsey ◽  
L. Kilpatrick ◽  
D. F. Wilson ◽  
M. Erecinska
Keyword(s):  
Metabolic Rate ◽  
Coronary Flow ◽  
Myocardial Metabolism ◽  
Active Form ◽  
Systolic Pressure ◽  
Cardiac Metabolism ◽  
Mechanical Activity ◽  
Sprague Dawley ◽  
Perfused Heart ◽  
Colonic Temperature

The effects of sublethal endotoxemia on the regulation of coronary flow by myocardial metabolism were examined in the isolated perfused heart preparation. Fasted Sprague-Dawley rats were injected (ip) with either endotoxin (0.5 mg/kg of body wt) or 5% dextrose 12 h before heart perfusion. The efficacy of endotoxin treatment was determined by measurement of plasma [NH3] and [urea] and colonic temperature. During perfusion with buffer containing glucose-pyruvate, oxygen consumption and coronary flow were increased by 17 and 42%, respectively, in hearts from endotoxin-treated rats as compared with those from controls. In the hearts from endotoxemic animals, the mitochondrial [NAD+]/[NADH] was decreased by approximately 25%, and the active form of pyruvate dehydrogenase was increased by 36% as compared with control hearts. [ATP]f/[ADP]f[Pi] was unaltered. The enhanced metabolic rate was associated with comparable changes in peak systolic pressure development, maximal positive and negative dP/dt, and the tension-time index when measured in the isovolumetric preparation. In these hearts, stimulation of respiration by perfusion with an alternate source of fuel or inhibition by infusion of amytal elicited large, transient increases in the level of coronary flow that returned rapidly to prestimulus values. By contrast, in hearts from controls, the transient increase in flow was coupled to sustained vasodilation, i.e., approximately 30% rise in flow for either metabolic condition. In both groups, [ATP]f/[ADP]f[Pi] either increased or decreased with stimulation or inhibition of respiration, respectively. Adenosine (1.2 microM) produced a 35% increase in flow in the hearts from the control animals, whereas it was without significant effect in those from the endotoxin-treated animals. It is concluded that sublethal endotoxemia causes 1) an increased metabolic rate and enhanced mechanical activity in the heart and 2) an uncoupling of flow from regulation by cardiac metabolism.

scholarly journals The contribution of the mouse tail to thermoregulation is modest

2020 ◽  
Vol 319 (2) ◽  
pp. E438-E446
Author(s):  
Vojtěch Škop ◽  
Naili Liu ◽  
Juen Guo ◽  
Oksana Gavrilova ◽  
Marc L. Reitman
Keyword(s):  
Metabolic Rate ◽  
Heat Loss ◽  
Heat Dissipation ◽  
Whole Body ◽  
Total Heat Loss ◽  
Brown Adipose ◽  
Adrenergic Antagonist ◽  
Similar Body ◽  
And Control ◽  
Body Heat

Understanding mouse thermal physiology informs the usefulness of mice as models of human disease. It is widely assumed that the mouse tail contributes greatly to heat loss (as it does in rat), but this has not been quantitated. We studied C57BL/6J mice after tail amputation. Tailless mice housed at 22°C did not differ from littermate controls in body weight, lean or fat content, or energy expenditure. With acute changes in ambient temperature from 19 to 39°C, tailless and control mice demonstrated similar body temperatures (Tb), metabolic rates, and heat conductances and no difference in thermoneutral point. Treatment with prazosin, an α1-adrenergic antagonist and vasodilator, increased tail temperature in control mice by up to 4.8 ± 0.8°C. Comparing prazosin treatment in tailless and control mice suggested that the tail’s contribution to total heat loss was a nonsignificant 3.4%. Major heat stress produced by treatment at 30°C with CL316243, a β3-adrenergic agonist, increased metabolic rate and Tb and, at a matched increase in metabolic rate, the tailless mice showed a 0.72 ± 0.14°C greater Tb increase and 7.6% lower whole body heat conductance. Thus, the mouse tail is a useful biomarker of vasodilation and thermoregulation, but in our experiments contributes only 5–8% of whole body heat dissipation, less than the 17% reported for rat. Heat dissipation through the tail is important under extreme scenarios such as pharmacological activation of brown adipose tissue; however, non-tail contributions to heat loss may have been underestimated in the mouse.

scholarly journals Transient and cyclic effects on a PCM-cooled mobile device

2015 ◽  
Vol 19 (5) ◽  
pp. 1723-1731 ◽  
Author(s):  
C.P. Tso ◽  
F.L. Tan ◽  
J. Jony
Keyword(s):  
Heat Pipe ◽  
Heat Dissipation ◽  
Heat Storage ◽  
Power Level ◽  
Internal Heat ◽  
Transient Temperature ◽  
Storage Unit ◽  
Transient Temperature Distribution ◽  
The Individual ◽  
Change Material

A mock handset with heat storage unit (HSU) has been designed, fabricated, and experimented under various conditions to examine the effect of external heat sink on the handset?s transient temperature distribution, performance of the individual HSU under different power level and orientation, as well as under the more realistic cyclic heating. The cooling of the handset is through using a phase change material (PCM), n-eicosane, stored in the external HSU connected to the handset through a miniature heat pipe. The heat pipe channels the internal heat dissipation to the HSU where it is absorbed by the PCM. Results show that the temperature is significantly lowered with the PCM-based HSU.

scholarly journals Evaluation of Various Cooling Systems After Exercise-Induced Hyperthermia

2017 ◽  
Vol 52 (2) ◽  
pp. 108-116 ◽  
Author(s):  
Pearl M. S. Tan ◽  
Eunice Y. N. Teo ◽  
Noreffendy B. Ali ◽  
Bryan C. H. Ang ◽  
Iswady Iskandar ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Core Temperature ◽  
Cooling System ◽  
Rating Of Perceived Exertion ◽  
Body Core Temperature ◽  
Cooling Systems ◽  
Induced Hyperthermia ◽  
Objective Evidence ◽  
Body Core ◽  
Exercise Induced

Context: Rapid diagnosis and expeditious cooling of individuals with exertional heat stroke is paramount for survival. Objective: To evaluate the efficacy of various cooling systems after exercise-induced hyperthermia. Design: Crossover study. Setting: Laboratory. Patients or Other Participants: Twenty-two men (age = 24 ± 2 years, height = 1.76 ± 0.07 m, mass = 70.7 ± 9.5 kg) participated. Intervention(s): Each participant completed a treadmill walk until body core temperature reached 39.50°C. The treadmill walk was performed at 5.3 km/h on an 8.5% incline for 50 minutes and then at 5.0 km/h until the end of exercise. Each participant experienced 4 cooling phases in a randomized, repeated-crossover design: (1) no cooling (CON), (2) body-cooling unit (BCU), (3) EMCOOLS Flex.Pad (EC), and (4) ThermoSuit (TS). Cooling continued for 30 minutes or until body core temperature reached 38.00°C, whichever occurred earlier. Main Outcome Measure(s): Body core temperature (obtained via an ingestible telemetric temperature sensor) and heart rate were measured continuously during the exercise and cooling phases. Rating of perceived exertion was monitored every 5 minutes during the exercise phase and thermal sensation every minute during the cooling phase. Results: The absolute cooling rate was greatest with TS (0.16°C/min ± 0.06°C/min) followed by EC (0.12°C/min ± 0.04°C/min), BCU (0.09°C/min ± 0.06°C/min), and CON (0.06°C/min ± 0.02°C/min; P &lt; .001). The TS offered a greater cooling rate than all other cooling modalities in this study, whereas EC offered a greater cooling rate than both CON and BCU (P &lt; .0083 for all). Effect-size calculations, however, showed that EC and BCU were not clinically different. Conclusion: These findings provide objective evidence for selecting the most effective cooling system of those we evaluated for cooling individuals with exercise-induced hyperthermia. Nevertheless, factors other than cooling efficacy need to be considered when selecting an appropriate cooling system.

Heat sensitive persons with multiple sclerosis are more tolerant to resistance exercise than to endurance exercise

2012 ◽  
Vol 19 (7) ◽  
pp. 932-940 ◽  
Author(s):  
Anders G Skjerbæk ◽  
Andreas B Møller ◽  
Ellen Jensen ◽  
Kristian Vissing ◽  
Henrik Sørensen ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Resistance Exercise ◽  
Core Temperature ◽  
Endurance Exercise ◽  
Subjective Symptom ◽  
Body Sway ◽  
Heat Sensitivity ◽  
Exercise Participation ◽  
Symptom Intensity ◽  
Exercise Induced

Background: Heat sensitivity (HS) is reported by 58% of all persons with multiple sclerosis (MS), causing symptom exacerbation possibly limiting exercise participation. Objective: The purpose of this study was to test the hypotheses that (a) a relationship between exercise-induced changes in core–temperature (Ctemp) and changes in symptom intensity exists, and (b) that resistance exercise (RE), as a consequence of a minor increase in core temperature, will induce a lesser worsening of symptoms than endurance exercise (EE) in HS persons with MS. Methods: On two separate days, 16 HS persons with MS randomly completed a session of RE and EE, or EE and RE, respectively. Testing was conducted pre, post and one hour after exercise and consisted of Visual Analogue Scale (VAS) scoring (fatigue, spasticity, pain, strength, walking and balance), the 5-time sit-to-stand (5STS), the Multiple Sclerosis Functional Composite (MSFC) and Body Sway. Composite scores describing average subjective symptom intensity (SI) and total number of symptoms (SN) were calculated from VAS scores. Results: Ctemp (0.9±0.4°C vs 0.3±0.1°C, p<0.001), SI (1.7±1.9 cm vs 0.6±1.5 cm, p<0.05) and SN (1.6±1.9 vs 0.6±2.1, p<0.05) increased significantly more during EE than RE. Changes in Ctemp correlated to changes in SI ( r=0.50, p<0.01). No differences were observed in 5STS, MSFC and Body Sway scores after EE when compared to RE. Conclusion: An exercise-induced increase in Ctemp is associated with increased number and severity of perceived symptoms in HS persons with MS. Based on these findings it is expected that HS persons with MS do tolerate RE better than EE.

The effectiveness of hand cooling at reducing exercise-induced hyperthermia and improving distance-race performance in wheelchair and able-bodied athletes

2008 ◽  
Vol 105 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Victoria Goosey-Tolfrey ◽  
Michelle Swainson ◽  
Craig Boyd ◽  
Greg Atkinson ◽  
Keith Tolfrey
Keyword(s):  
Relative Humidity ◽  
Core Temperature ◽  
Recovery Period ◽  
Exercise Protocol ◽  
Detailed Measurement ◽  
Exercise Induced ◽  
Performance Times ◽  
Induced Changes ◽  
Race Performance ◽  
Performance Trial

The purpose of this study was to examine the effectiveness of reducing core temperature in postexercise hyperthermic subjects and to assess if hand cooling (HC) improves subsequent timed distance performance. Following a detailed measurement check on the use of insulated auditory canal temperature (Tac), eight wheelchair (WA) athletes and seven male able-bodied (AB) athletes performed two testing sessions, comprising a 60-min exercise protocol and 10-min recovery period, followed by a performance trial (1 km and 3 km for WA and AB, respectively) at 30.8°C (SD 0.2) and 60.6% (SD 0.2) relative humidity. In a counterbalanced order, HC and a no-cooling condition was administered during the 10-min recovery period before the performance trial. Nonsignificant condition × time interactions for both WA ( F15,75 = 1.5, P = 0.14) and AB ( F15,90 = 1.2, P = 0.32) confirmed that the exercise-induced changes (Δ) in Tac were similar before each intervention. However, the exercise-induced increase was evidently greater in AB compared with WA (2.0 vs. 1.3°C change, respectively). HC produced ΔTac of −0.4°C (SD 0.4) and −1.2°C (SD 0.2) in comparison (WA and AB, respectively), and simple-effects analyses suggested that the reductions in Tac were noteworthy after 4 min of HC. HC had an impact on improving AB performances by −4.0 s (SD 11.5) ( P < 0.05) and WA by −20.5 s (SD 24.2) ( P > 0.05). In conclusion, extraction of heat through the hands was effective in lowering Tac in both groups and improving 3-km performance in the AB athletes and trends toward positive gains for the 1-km performance times of the WA group.

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