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Kuzmenko NV, Shcherbak NS, Pliss MG, Tsyrlin VA, Galagudza MM. A Meta-Analysis of Cardiovascular Adaptive Responses to Temperature Variations in Normotensive Rats. Biophysics (Nagoya-shi) 2021. [DOI: 10.1134/s0006350921060099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Gender differences in brown adipose tissue-related brain functional networks: an 18F-FDG-PET study. Nucl Med Commun 2021; 41:526-532. [PMID: 32282630 DOI: 10.1097/mnm.0000000000001190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE Thermogenesis of brown adipose tissue (BAT) is controlled by central modulating mechanisms, although changes in brain metabolism of BAT-positive subjects with different genders are still unclear. We hypothesized that changes in regional cerebral glucose metabolic activity were associated with BAT activities, and this association differed in different genders. METHODS Brain glucose metabolism of 26 BAT-positive and 26 BAT-negative healthy subjects was compared using a brain fluorodeoxyglucose (FDG)-PET scan, and gender differences in BAT-related brain functional networks and effect of sex hormones were assessed by comparing the brain PET images of BAT-positive and BAT-negative subjects of different genders and postmenopausal female subjects. RESULTS Compared with controls, BAT-positive male subjects had a significant hypermetabolic area in the right extranuclear and significant hypometabolic areas in the right inferior parietal lobule and right inferior frontal gyrus; while at the same threshold, BAT-positive female subjects had richer hypermetabolic regions, including bilateral limbic lobes, bilateral frontal lobes, right cerebellum, left sublobar, and right parietal lobe. However, BAT-positive postmenopause female subjects only showed significant hypometabolic regions in left lingual gyrus. CONCLUSIONS BAT-related brain functional networks are different between male and female subjects. Female networks are more significant and more concentrated while male networks are smaller and more dispersed, and these gender differences may be related to sex hormones.
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Ono-Moore KD, Rutkowsky JM, Pearson NA, Williams DK, Grobe JL, Tolentino T, Lloyd KCK, Adams SH. Coupling of energy intake and energy expenditure across a temperature spectrum: impact of diet-induced obesity in mice. Am J Physiol Endocrinol Metab 2020; 319:E472-E484. [PMID: 32691631 PMCID: PMC7509245 DOI: 10.1152/ajpendo.00041.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Obesity and its metabolic sequelae are implicated in dysfunction of the somatosensory, sympathetic, and hypothalamic systems. Because these systems contribute to integrative regulation of energy expenditure (EE) and energy intake (EI) in response to ambient temperature (Ta) changes, we hypothesized that diet-induced obesity (DIO) disrupts Ta-associated EE-EI coupling. C57BL/6N male mice were fed a high-fat diet (HFD; 45% kcal) or low-fat diet (LFD; 10% kcal) for ∼9.5 wk; HFD mice were then split into body weight (BWT) quartiles (n = 8 each) to study DIO-low gainers (Q1) versus -high gainers (Q4). EI and indirect calorimetry (IC) were measured over 3 days each at 10°C, 20°C, and 30°C. Responses did not differ between LFD, Q1, and Q4; EI and BWT-adjusted EE increased rapidly when transitioning toward 20°C and 10°C. In all groups, EI at 30°C was not reduced despite lower EE, resulting in positive energy balance and respiratory exchange ratios consistent with increased de novo lipogenesis, energy storage, and relative hyperphagia. We conclude that 1) systems controlling Ta-dependent acute EI/EE coupling remained intact in obese mice and 2) rapid coupling of EI/EE at cooler temperatures is an important adaptation to maintain energy stores and defend body temperature, but less critical at thermoneutrality. A post hoc analysis using digestible EI plus IC-calculated EE suggests that standard IC assumptions for EE calculation require further validation in the setting of DIO. The experimental paradigm provides a platform to query the hypothalamic, somatosensory, and sympathetic mechanisms that drive Ta-associated EI/EE coupling.
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Affiliation(s)
| | - Jennifer M Rutkowsky
- Department of Molecular Biosciences, UC Davis School of Veterinary Medicine, University of California, Davis, California
- Mouse Metabolic Phenotyping Center, University of California, Davis, California
| | - Nicole A Pearson
- Department of Pharmacology, University of Iowa, Carver College of Medicine, Iowa City, Iowa
| | - D Keith Williams
- Arkansas Children's Nutrition Center, Little Rock, Arkansas
- Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Justin L Grobe
- Department of Physiology and Biomedical Engineering, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Todd Tolentino
- Mouse Metabolic Phenotyping Center, University of California, Davis, California
| | - K C Kent Lloyd
- Mouse Metabolic Phenotyping Center, University of California, Davis, California
- Department of Surgery, School of Medicine, University of California, Davis, California
| | - Sean H Adams
- Arkansas Children's Nutrition Center, Little Rock, Arkansas
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
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Gholampour R, Darand M, Halabian AH. Impacts of cold and hot temperatures on mortality rate in Isfahan, Iran. J Therm Biol 2019; 86:102453. [DOI: 10.1016/j.jtherbio.2019.102453] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 10/23/2019] [Accepted: 10/31/2019] [Indexed: 12/16/2022]
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Dzenda T, Ayo JO, Sinkalu VO, Yaqub LS. Diurnal, seasonal, and sex patterns of heart rate in grip-restrained African giant rats (Cricetomys gambianus, Waterhouse). Physiol Rep 2015; 3:e12581. [PMID: 26471756 PMCID: PMC4632951 DOI: 10.14814/phy2.12581] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 09/09/2015] [Accepted: 09/12/2015] [Indexed: 11/24/2022] Open
Abstract
This study was carried out to determine heart rate (HR) values, including diurnal, seasonal, and sex patterns, in the African giant rat (Cricetomys gambianus, Waterhouse). HR was measured using stethoscope in grip-restrained African giant rats of either sex (103 bucks and 98 does), live-trapped from a tropical Savannah, and caged individually in the laboratory during the harmattan (cold-dry), hot-dry, and rainy seasons over a 3-year period. The HR fluctuated between 90 and 210 beats per minute (bpm) throughout the study period. Diurnal changes in HR (mean ± SEM) during the hot-dry and rainy seasons were nonsignificant (P > 0.05), but the morning and afternoon values differed (P < 0.01) during the cold-dry season. The HR varied (P < 0.05) among seasons, with peak, nadir, and moderate values recorded during the cold-dry (165.8 ± 0.51 bpm), hot-dry (153.1 ± 0.74 bpm), and rainy (163.4 ± 0.70 bpm) seasons, respectively. Mean HR of bucks was lower than that of does during the cold-dry (P < 0.0001) and hot-dry (P < 0.01) seasons, but sex difference during the rainy season was insignificant (P > 0.05). Overall, mean HR was lower (P < 0.0001) in bucks (158.8 ± 0.53 bpm) than in does (164.8 ± 0.53 bpm). In conclusion, values of HR in African giant rats are shown for the first time. Season, sex, and daytime influenced the HR, and should be considered during clinical evaluations of the rats.
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Affiliation(s)
- Tavershima Dzenda
- Department of Veterinary Physiology, Ahmadu Bello University, Zaria, Nigeria
| | - Joseph O Ayo
- Department of Veterinary Physiology, Ahmadu Bello University, Zaria, Nigeria
| | - Victor O Sinkalu
- Department of Veterinary Physiology, Ahmadu Bello University, Zaria, Nigeria
| | - Lukuman S Yaqub
- Department of Veterinary Physiology, Ahmadu Bello University, Zaria, Nigeria
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Contreras C, Gonzalez F, Fernø J, Diéguez C, Rahmouni K, Nogueiras R, López M. The brain and brown fat. Ann Med 2015; 47:150-68. [PMID: 24915455 PMCID: PMC4438385 DOI: 10.3109/07853890.2014.919727] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2013] [Accepted: 04/25/2014] [Indexed: 02/06/2023] Open
Abstract
Brown adipose tissue (BAT) is a specialized organ responsible for thermogenesis, a process required for maintaining body temperature. BAT is regulated by the sympathetic nervous system (SNS), which activates lipolysis and mitochondrial uncoupling in brown adipocytes. For many years, BAT was considered to be important only in small mammals and newborn humans, but recent data have shown that BAT is also functional in adult humans. On the basis of this evidence, extensive research has been focused on BAT function, where new molecules, such as irisin and bone morphogenetic proteins, particularly BMP7 and BMP8B, as well as novel central factors and new regulatory mechanisms, such as orexins and the canonical ventomedial nucleus of the hypothalamus (VMH) AMP- activated protein kinase (AMPK)-SNS-BAT axis, have been discovered and emerged as potential drug targets to combat obesity. In this review we provide an overview of the complex central regulation of BAT and how different neuronal cell populations co-ordinately work to maintain energy homeostasis.
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Affiliation(s)
- Cristina Contreras
- Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria , Santiago de Compostela, 15782 , Spain
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Valve disease and hypotension hospital admissions peaked at physiologically equivalent temperature 0-5 °C in Germany in 2009-2011. Int J Cardiol 2014; 177:169-70. [PMID: 25499370 DOI: 10.1016/j.ijcard.2014.09.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Accepted: 09/16/2014] [Indexed: 11/22/2022]
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Luo B, Zhang S, Ma S, Zhou J, Wang B. Effects of different cold-air exposure intensities on the risk of cardiovascular disease in healthy and hypertensive rats. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2014; 58:185-194. [PMID: 23435512 DOI: 10.1007/s00484-013-0641-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 01/17/2013] [Accepted: 01/31/2013] [Indexed: 06/01/2023]
Abstract
Ten-week-old male Wistar rats (systolic blood pressure, 106-116 mmHg; body weight, 300-320 g) and spontaneously hypertensive rats (systolic blood pressure, 160-176 mmHg; body weight, 210.9-244.9 g) were used as healthy and hypertensive subjects to determine the effects of varying degrees of cold-air exposure in a climate chamber box. The three cold-air ranks were cold air I [minimum temperature (TMIN) 6.4 °C, ↓∆T48 8.6 °C], cold air II (TMIN 3.8 °C, ↓∆T48 11.2 °C), and cold air III (TMIN -0.3 °C, ↓∆T48 15.3 °C), as established from the cold-air data of Zhangye City, China. Each cold-air rank consisted of a temperature drop and a temperature increase with the same initial and terminal temperatures (15 °C). After cold-air exposure, the risk factors for cardiovascular disease (CVD) such as systolic blood pressure, whole blood viscosity (10/s and 150/s), plasma fibrinogen, and blood lipids of the rats were determined. The results indicated that the CVD risk factors of the healthy and hypertensive rats increased significantly with cold-air exposure intensities. The increase in systolic blood pressure was greater during temperature drops, whereas the increases in whole blood viscosity and plasma fibrinogen were greater after cold-air exposure. The effects of cold-air exposure on the CVD risk factors of healthy rats, particularly the systolic blood pressure, whole blood viscosity (150/s), and LDL/HDL, were greater than those in hypertensive rats. In conclusion, CVD risk may increase with cold-air ranks. Blood pressure-induced CVD risk may be greater during cold-air temperature drop, whereas atherosclerosis-induced CVD risk may be greater after cold-air exposure. The effect of cold air on the CVD risk factors in healthy subjects may be more significant than those in hypertensive subjects.
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Affiliation(s)
- Bin Luo
- School of Applied Meteorology, Nanjing University of Information Science and Technology, 219 Ningliulu, Nanjing, China
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Jackson KL, Nguyen-Huu TP, Davern PJ, Head GA. Energy metabolism in BPH/2J genetically hypertensive mice. Hypertens Res 2013; 37:413-21. [DOI: 10.1038/hr.2013.156] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Revised: 10/21/2013] [Accepted: 10/29/2013] [Indexed: 11/09/2022]
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Jeong TS, Park CW, Yoo CJ, Kim EY, Kim YB, Kim WK. Association between the daily temperature range and occurrence of spontaneous intracerebral hemorrhage. J Cerebrovasc Endovasc Neurosurg 2013; 15:152-7. [PMID: 24167793 PMCID: PMC3804651 DOI: 10.7461/jcen.2013.15.3.152] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 07/01/2013] [Accepted: 08/07/2013] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVE We have observed, anecdotally, that the incidence of primary spontaneous intracerebral hemorrhage (sICH), as well as spontaneous subarachnoid hemorrhage, varies in accordance with seasonality and meteorological conditions. This retrospective single-hospital-based study aimed to determine the seasonality of sICH and the associations, if any, between the occurrence of sICH and meteorological parameters in Incheon city, which is a northwestern area of South Korea. METHODS Electronic hospital data on 708 consecutive patients admitted with primary sICH from January 2008 to December 2010 was reviewed. Traumatic and various secondary forms of ICHs were excluded. Average monthly admission numbers of sICH were analyzed, in relation with the local temperature, atmospheric pressure, humidity, and daily temperature range data. The relationships between the daily values of each parameter and daily admission numbers of sICH were investigated using a combination of correlation and time-series analyses. RESULTS No seasonal trend was observed in sICH-related admissions during the study period. Furthermore, no statistically significant correlation was detected between the daily sICH admission numbers and the meteorological parameters of temperature, atmospheric pressure and humidity. The daily temperature range tended to correlate with the number of daily sICH-related admissions (p = 0.097). CONCLUSION This study represents a comprehensive investigation of the association between various meteorological parameters and occurrence of spontaneous ICH. The results suggest that the daily temperature range may influence the risk of sICH.
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Affiliation(s)
- Tae Seok Jeong
- Department of Neurosurgery, Gil Medical Center, Gachon University, Incheon, Korea
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Gill RS, Hambridge HL, Schneider EB, Hanff T, Tamargo RJ, Nyquist P. Falling temperature and colder weather are associated with an increased risk of aneurysmal subarachnoid hemorrhage. World Neurosurg 2012; 79:136-42. [PMID: 22732514 DOI: 10.1016/j.wneu.2012.06.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 04/07/2012] [Accepted: 06/13/2012] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To use weather data to predict increased incidence of aneurysmal subarachnoid hemorrhage (aSAH) at a large institution with an extensive referral network in response to falling temperatures. METHODS In a retrospective study, 1175 prospectively collected aSAH cases accrued over 18 years from one hospital were reviewed to determine if season, maximum ambient temperature (MAT), average relative humidity, and atmospheric pressure were related to incidence of aSAH at that institution on a given day. A Poisson regression model was used to assess daily risk of incident aSAH based on daily MAT and 1-day change in MAT. RESULTS A MAT decrease of 1°F from one day to the next was associated with a 0.6% increase in risk of aSAH (relative risk [RR]=1.006, P=0.016). The increased risk associated with MAT decrease from the previous day was especially strong for female patients (RR=1.008/°F, P=0.007) and drove the overall model, representing 72% of cases. In addition, warmer temperatures were associated with a decreased risk of aSAH; each 1°F increase in temperature compared with the previous day was associated with a 0.3% decrease in risk of aSAH (RR=0.997; P<0.001). CONCLUSIONS A 1-day decrease in temperature and colder daily temperatures were associated with an increased risk of incident aSAH at a single institution with a large referral network. These variables appeared to act synergistically and independently of season. These relationships were particularly predominant in the fall when the transition from warmer to colder temperatures occurred.
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Affiliation(s)
- Randeep S Gill
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Hauton D, May S, Sabharwal R, Deveci D, Egginton S. Cold-impaired cardiac performance in rats is only partially overcome by cold acclimation. J Exp Biol 2011; 214:3021-31. [DOI: 10.1242/jeb.053587] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
SUMMARY
The consequences of acute hypothermia include impaired cardiovascular performance, ultimately leading to circulatory collapse. We examined the extent to which this results from intrinsic limitations to cardiac performance or physiological dysregulation/autonomic imbalance, and whether chronic cold exposure could ameliorate the impaired function. Wistar rats were held at a 12 h:12 h light:dark (L:D) photoperiod and room temperature (21°C; euthermic controls), or exposed to a simulated onset of winter in an environmental chamber by progressive acclimation to 1 h:23 h L:D and 4°C over 4 weeks. In vivo, acute cold exposure (core temperature, Tb=25°C) resulted in hypotension (approximately –20%) due to low cardiac output (approximately –30%) accompanying a bradycardia (approximately –50%). Cold acclimation (CA) induced only partial compensation for this challenge, including increased coronary flow at Tb=37°C (but not at Tb=25°C), maintenance of ventricular capillarity and altered sympathovagal balance (increased low:high frequency in power spectral analysis, PSA), suggesting physiological responses alone were insufficient to maintain cardiovascular performance. However, PSA showed maintenance of cardiorespiratory coupling on acute cold exposure in both groups. Ex vivo cardiac performance revealed no change in intrinsic heart rate, but a mechanical impairment of cardiac function at low temperatures following CA. While CA involved an increased capacity for β-oxidation, there was a paradoxical reduction in developed pressure as a result of adrenergic down-regulation. These data suggest that integrated plasticity is the key to cardiovascular accommodation of chronic exposure to a cold environment, but with the potential for improvement by intervention, for example with agents such as non-catecholamine inotropes.
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Affiliation(s)
- David Hauton
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
| | - Shaun May
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
| | - Rasna Sabharwal
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
| | - Durmus Deveci
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
| | - Stuart Egginton
- Centre for Cardiovascular Sciences, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, UK
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Jaehne EJ, Majumder I, Salem A, Irvine RJ. Increased effects of 3,4-methylenedioxymethamphetamine (ecstasy) in a rat model of depression. Addict Biol 2011; 16:7-19. [PMID: 20192951 DOI: 10.1111/j.1369-1600.2009.00196.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is associated with increases in core body temperature (T(C)) and depressive mood states in users. Flinders Sensitive Line (FSL) rats represent a rat model of depression originally bred from Sprague-Dawley (SD) rats. They are more sensitive to both muscarinic and serotonergic agonists and have altered thermoregulatory responses to various drugs. To examine the link between MDMA and depression, eight FSL and eight SD rats were administered saline and 5 and 7.5 mg/kg MDMA. Immediately following administration, rats were confined to an area with an ambient temperature (T(A)) of 30 ± 1°C for 30 minutes before being allowed access to a thermal gradient for four hours. The brains were removed one week after final dose of MDMA and concentrations of serotonin and dopamine were measured. Treatment with MDMA at both doses led to a higher T(C) in the FSL rats than the SD rats at high T(A) (P < 0.01). Fatalities due to hyperthermia occurred in the FSL rats after both doses, whereas all but one of the SD rats recovered well. Heart rate was also much higher after MDMA in the FSL rats throughout the experiments. The FSL rats showed significant decreases in all transmitters measured (P < 0.05). These differences between strains were not accounted for by altered blood or brain concentrations of MDMA. The results indicate that the FSL rats may be more susceptible to developing MDMA-induced hyperthermia and possible damage to the brain. These findings may be of importance to human users of MDMA who also have depression.
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Bauchinger U, Keil J, McKinney RA, Starck JM, McWilliams SR. Exposure to cold but not exercise increases carbon turnover rates in specific tissues of a passerine. J Exp Biol 2010; 213:526-34. [DOI: 10.1242/jeb.037408] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Carbon turnover differs between tissues within an animal, but the extent to which ecologically relevant increases in metabolism affect carbon turnover rates is largely unknown. We tested the energy expenditure and protein turnover hypotheses that predict increased carbon turnover, either in association with increased daily energy expenditure, or in concert with tissue-specific increased protein metabolism. We used stable-isotope-labeled diets to quantify the rate of carbon turnover in 12 different tissues for three groups of zebra finches (Taeniopygia guttata): cold-exposed birds kept at ambient temperatures below their thermoneutral zone, exercised birds that were flown for 2 h per day in a flight arena, and control birds that were kept at ambient temperatures within their thermoneutral zone and that were not exercised. We found that increases in metabolism associated with cold-exposure but not exercise produced measurable increases in carbon turnover rate of, on average, 2.4±0.3 days for pectoral muscle, gizzard, pancreas and heart, even though daily energy intake was similar for exercised and cold-exposed birds. This evidence does not support the energy expenditure hypothesis, and we invoke two physiological processes related to protein metabolism that can explain these treatment effects: organ mass increase and tissue-specific increase in activity. Such changes in carbon turnover rate associated with cold temperatures translate into substantial variation in the estimated time window for which resource use is estimated and this has important ecological relevance.
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Affiliation(s)
- U. Bauchinger
- Department Biology II, University of Munich (LMU), Großhaderner Straße 2, 82152 Planegg-Martinsried, Germany
- University of Rhode Island (URI), Kingston, RI 02881, USA
| | - J. Keil
- Department Biology II, University of Munich (LMU), Großhaderner Straße 2, 82152 Planegg-Martinsried, Germany
| | - R. A. McKinney
- US Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Lab, Atlantic Ecology Division, Narragansett, RI 02882, USA
| | - J. M. Starck
- Department Biology II, University of Munich (LMU), Großhaderner Straße 2, 82152 Planegg-Martinsried, Germany
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Effects of Taurine on Cardiovascular and Autonomic Nervous Functions in Cold Exposed rats. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 643:533-40. [DOI: 10.1007/978-0-387-75681-3_55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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The effect of long-term repeated exposure to 3,4-methylenedioxymethamphetamine on cardiovascular and thermoregulatory changes. Psychopharmacology (Berl) 2008; 201:161-70. [PMID: 18679656 DOI: 10.1007/s00213-008-1258-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Accepted: 07/08/2008] [Indexed: 10/21/2022]
Abstract
RATIONALE 3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") disrupts thermoregulation in rats and can lead to life-threatening hyperthermia in humans. MDMA administration can also lead to long-term neurotoxicity in animals and possibly humans. OBJECTIVES The purpose of the current study was to extend previous results on the acute effects of MDMA on behavioral thermoregulation to a repeated dosing regime, simulating regular weekend use of ecstasy, on measures of thermoregulation and heart rate (HR). MATERIALS AND METHODS Sprague-Dawley rats with telemetry implants were administered 40 micromol/kg MDMA on three consecutive days each week for 1 or 6 weeks before being confined to an elevated ambient temperature (TA) (HOT; 30+/-1 degrees C) or an area at room temperature (ROOM; 21.5+/-1.5 degrees C) for 30 min. After the final drug administration, rats were placed in a thermal gradient for 4 h to allow behavioral thermoregulation. RESULTS HOT rats showed higher core temperature (TC), HR, and locomotor activity than ROOM rats during confinement to a set TA (P<0.001). HR responses to MDMA over 6 weeks at both TAs progressively decreased with repeated dosing (P<0.05). TC was significantly higher in both 6-week groups compared to the 1-week groups (P<0.05) at the end of time in the gradient. Cortical concentrations of dihydroxyphenylacetic acid (DOPAC; P<0.05) and 5-hydroxyindole acetic acid (5-HIAA; P<0.001) decreased significantly irrespective of TA, while concentrations of dopamine and 5-HT did not change. CONCLUSION Long-term treatment with MDMA resulted in apparent tolerance to the effects of the drug on HR, dysregulation of TC in thermal gradient, and depletion of cortical DOPAC and 5-HIAA.
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Cheng Y, Hauton D. Cold acclimation induces physiological cardiac hypertrophy and increases assimilation of triacylglycerol metabolism through lipoprotein lipase. Biochim Biophys Acta Mol Cell Biol Lipids 2008; 1781:618-26. [PMID: 18722549 PMCID: PMC2568868 DOI: 10.1016/j.bbalip.2008.07.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 07/15/2008] [Accepted: 07/15/2008] [Indexed: 12/24/2022]
Abstract
The contribution of triacylglycerol to energy provision in the hypertrophied heart, mediated through lipoprotein lipase (LPL) is largely unknown and the contribution of very-low-density lipoprotein (VLDL) receptor to control of LPL presentation at the endothelium is unclear. For isolated perfused rat hearts, cold acclimation (CA) induced volume-overload hypertrophy, with decreased developed pressure (P < 0.01), increased end-diastolic volume of the left ventricle (P < 0.001) and a loss of contractile reserve in response to dobutamine challenge (P < 0.01). Oleate utilisation by perfused hearts was unchanged by CA, however uptake of intralipid emulsion increased 3-fold (P < 0.01). CA increased the proportion of lipid deposited in tissue lipids from 10% in euthermic controls to 40% (P < 0.01) although the overall contribution of individual lipid classes was unaffected. Cold acclimation significantly increased heparin-releasable LPL (P < 0.05) and tissue residual LPL (P < 0.01). Western blot analysis indicated preserved expression of proteins coding for SERCA2, muscle-CPT1 and VLDL-receptor following CA, while AMPKα2 and phospho-AMPKα2 were unaffected. These observations indicate that for physiological hypertrophy AMPK phosphorylation does not mediate the enhanced translocation of LPL to cardiac endothelium.
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Affiliation(s)
- Y Cheng
- Department of Physiology, Division of Medical Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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Abe T, Ohde S, Ishimatsu S, Ogata H, Hasegawa T, Nakamura T, Tokuda Y. Effects of meteorological factors on the onset of subarachnoid hemorrhage: a time-series analysis. J Clin Neurosci 2008; 15:1005-10. [PMID: 18617401 DOI: 10.1016/j.jocn.2007.07.081] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Revised: 07/17/2007] [Accepted: 07/20/2007] [Indexed: 10/21/2022]
Abstract
Previous studies have suggested a possible association between meteorological factors and the onset of subarachnoid hemorrhage (SAH). We aimed to investigate the relationship between the onset of SAH and meteorological factors based on an hourly time-series analysis. We collected hourly data on transportation of patients with SAH using the ambulance records of the Tokyo Fire Department from January 1 to December 31, 2005. We also collected hourly meteorological data for Tokyo from the Japan Meteorological Agency during the same period. We performed a time-series analysis using the autoregressive integrated moving average (ARIMA) model to control for autocorrelations in the time-series data. There were 1729 patients with SAH (mean age 63.3 years; 60.2% women). We identified two circadian patterns in the onset of SAH: a daily peak at 10 am (p<0.001) and a seasonal peak in February (p<0.001). Based on the ARIMA time-series analysis, significant risk factors associated with the onset of SAH included: low temperature on the previous day (lag time 17h; p=0.005) and on the onset day (lag time 0h; p<0.001); high barometric pressure on the onset day (lag time 0h; p=0.001). Humidity was not associated with the onset of SAH. Among meteorological factors, low temperature and high barometric pressure may be risk factors for the onset of SAH.
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Affiliation(s)
- Toshikazu Abe
- Department of Emergency and Critical Care Medicine, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo City, Tokyo 104-8560, Japan.
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Saito T, Ishiwata T, Hasegawa H, Nomoto S, Kotani Y, Otokawa M, Aihara Y. Effect of chronic cold exposure on noradrenergic modulation in the preoptic area of thermoregulation in freely moving rats. Life Sci 2008; 83:79-84. [PMID: 18571204 DOI: 10.1016/j.lfs.2008.05.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 04/17/2008] [Accepted: 05/15/2008] [Indexed: 01/22/2023]
Abstract
For this study, we compared the thermoregulatory involvement of noradrenaline (NA) in the medial preoptic area (mPOA) of non-cold acclimated rats to that of cold-acclimated rats. We quantified the release of NA in the mPOA during 3 h cold (5 degrees C) exposure in room-temperature-acclimated rats (RA group, kept at 23 degrees C for 2 weeks) and cold-acclimated rats (CA group, kept at 5 degrees C for 2 weeks). We concurrently monitored the core body temperature (Tc), heart rate (HR), and tail skin temperature (Tt). Cold exposure significantly increased Tc and HR, and decreased Tt in both groups. However, the cold-induced increase of the extracellular NA levels in mPOA was observed only in the RA group: not in the CA group. To elucidate these different results in NA levels further, and to evaluate participation of the mPOA in thermoregulation in the cold, we measured Tc, HR, and Tt during perfusion of alpha-adrenoceptor antagonist phenoxybenzamine during cold exposure (5 degrees C). This pharmacological procedure induced marked hypothermia, with decreases in HR only in the RA group; no changes were observed in Tc or any thermoregulatory parameter in the CA group. These results suggest that NA in the mPOA modulates heat production in response to acute cold stress in the RA group. However, this thermoregulatory action of NA in the mPOA was attenuated in the CA group.
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Affiliation(s)
- Takehito Saito
- Department of Kinesiology, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan.
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Jaehne EJ, Salem A, Irvine RJ. Pharmacological and behavioral determinants of cocaine, methamphetamine, 3,4-methylenedioxymethamphetamine, and para-methoxyamphetamine-induced hyperthermia. Psychopharmacology (Berl) 2007; 194:41-52. [PMID: 17530474 DOI: 10.1007/s00213-007-0825-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Accepted: 05/06/2007] [Indexed: 11/25/2022]
Abstract
RATIONALE Cocaine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA, ecstasy), and para-methoxyamphetamine (PMA) disrupt normal thermoregulation in humans, with PMA being associated with more severe cases of hyperthermia. Harm minimization advice on how to prevent overheating depends on appropriate thermoregulatory behavior by drug users. OBJECTIVES The purpose of the current study was to establish dose-response relationships for the effects of a number of commonly used illicit stimulants and investigate the behavioral response to increased core temperature. MATERIALS AND METHODS Sprague-Dawley rats with telemetry implants were administered either saline or 4, 12, 26, 40 or 80 micromol/kg of cocaine, methamphetamine, MDMA, or PMA and confined to an ambient temperature of 30 degrees C for 30 min, before being able to choose their preferred temperature on a thermally graded runway (11-41 degrees C). RESULTS The increased core temperature caused by administration of cocaine, methamphetamine, and MDMA treatment led to the animals seeking the cool end of the runway to correct their core temperature, although this did not occur in PMA-treated rats. The order of potency for increasing core temperature was methamphetamine >PMA = MDMA>cocaine. This differed to the slopes of the dose-response curves where MDMA and PMA showed the steepest slope for the doses used followed by methamphetamine then cocaine. CONCLUSIONS These results suggest that behavioral aspects of thermoregulation are important in assessing the potential of individual drugs to cause harmful increases in core temperature.
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Affiliation(s)
- Emily Joy Jaehne
- Discipline of Pharmacology, School of Medical Sciences, University of Adelaide, Level 5 Medical School North, Adelaide, South Australia 5005, Australia.
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Dimicco JA, Zaretsky DV. The dorsomedial hypothalamus: a new player in thermoregulation. Am J Physiol Regul Integr Comp Physiol 2007; 292:R47-63. [PMID: 16959861 DOI: 10.1152/ajpregu.00498.2006] [Citation(s) in RCA: 217] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurons in the dorsomedial hypothalamus (DMH) play key roles in physiological responses to exteroceptive (“emotional”) stress in rats, including tachycardia. Tachycardia evoked from the DMH or seen in experimental stress in rats is blocked by microinjection of the GABAA receptor agonist muscimol into the rostral raphe pallidus (rRP), an important thermoregulatory site in the brain stem, where disinhibition elicits sympathetically mediated activation of brown adipose tissue (BAT) and cutaneous vasoconstriction in the tail. Disinhibition of neurons in the DMH also elevates core temperature in conscious rats and sympathetic activity to least significant difference interscapular BAT (IBAT) and IBAT temperature in anesthetized preparations. The latter effects are blocked by microinjection of muscimol into the rRP, while microinjection of muscimol into either the rRP or DMH suppresses increases in sympathetic nerve activity to IBAT, IBAT temperature, and core body temperature elicited either by microinjection of PGE2 into the preoptic area (an experimental model for fever), or central administration of fentanyl. Neurons concentrated in the dorsal region of the DMH project directly to the rRP, a location corresponding to that of neurons transsynaptically labeled from IBAT. Thus these neurons control nonshivering thermogenesis in rats, and their activation signals its recruitment in diverse experimental paradigms. Evidence also points to a role for neurons in the DMH in thermoregulatory cutaneous vasoconstriction, shivering, and endocrine adjustments. These directions provide intriguing avenues for future exploration that may expand our understanding of the DMH as an important hypothalamic site for the integration of autonomic, endocrine, and behavioral responses to diverse challenges.
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Affiliation(s)
- Joseph A Dimicco
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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Perez-Lloret S, Toblli JE, Vigo DE, Cardinali DP, Milei J. Infradian awake and asleep systolic and diastolic blood pressure rhythms in humans. J Hypertens 2006; 24:1273-9. [PMID: 16794475 DOI: 10.1097/01.hjh.0000234106.00745.50] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Blood pressure shows 24-h rhythms with a significant seasonal fluctuation. OBJECTIVES To characterize 2-month to 12-month infradian rhythms in the mean awake and asleep systolic blood pressure (SBP) and diastolic blood pressure (DBP) in humans. METHODS A total of 1689 participants underwent 24-h ambulatory blood pressure monitoring during different periods of the year. The mean daily temperature, humidity, barometric pressure and wind velocity values for the same time span and geographical location were obtained. Fourier analysis was used to fit 12-month, 6-month, 4-month, 3-month and 2-month rhythms to the mean awake and asleep SBP and DBP and to metereological variables. RESULTS The awake mean SBP and DBP values showed significant 12-month and 3-month rhythms (respectively, R2 = 55%, P < 0.001 and R2 = 45% P < 0.001), with a peak in July (winter) and a trough-peak difference of 6.2 +/- 1.6 mmHg (P < 0.001, SBP) and 4.2 +/- 1.5 mmHg (P < 0.001, DBP). In contrast, asleep blood pressure means showed mainly 3-month rhythms (SBP, R2 = 19%, P < 0.02; DBP, R2 = 43% P < 0.02). Mean daily temperature and humidity showed at 12-month, 6-month, 4-month, 3-month and 2-month rhythms, barometric pressure showed 12-month and 6-month rhythms, and wind velocity showed 12-month and 3-month rhythms. Minimal temperature values and maximal humidity values coincided with elevated blood pressure values. CONCLUSION Awake blood pressure means exhibited mainly circannual fluctuations while asleep blood pressure means showed principally 3-month rhythms. Infradian blood pressure variations correlated with some meteorological variables.
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Affiliation(s)
- Santiago Perez-Lloret
- Instituto de Investigaciones Cardiologicas, Prof. Dr. Alberto C. Taquini, Facultad de Medicina, Universidad de Buenos Aires, Argentina
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Hasegawa H, Ishiwata T, Saito T, Yazawa T, Aihara Y, Meeusen R. Inhibition of the preoptic area and anterior hypothalamus by tetrodotoxin alters thermoregulatory functions in exercising rats. J Appl Physiol (1985) 2005; 98:1458-62. [PMID: 15618320 DOI: 10.1152/japplphysiol.00916.2004] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have previously demonstrated a functional role of the preoptic area and anterior hypothalamus (PO/AH) in thermoregulation in freely moving rats at various temperature conditions by using microdialysis and biotelemetry methods. In the present study, we perfused tetrodotoxin (TTX) solution into the PO/AH to investigate whether this manipulation can modify thermoregulation in exercising rats. Male Wistar rats were trained for 3 wk by treadmill running. Body core temperature (Tb), heart rate (HR), and tail skin temperature (Ttail) were measured. Rats ran for 120 min at speed of 10 m/min, with TTX (5 μM) perfused into the left PO/AH during the last 60 min of exercise through a microdialysis probe (control, n = 12; TTX, n = 12). Tb, HR, and Ttail increased during the first 20 min of exercise. Thereafter, Tb, HR, and Ttail were stable in both groups. Perfusion of TTX into the PO/AH evoked an additional rise in Tb (control: 38.2 ± 0.1°C, TTX: 39.3 ± 0.2°C; P < 0.001) with a significant decrease in Ttail (control: 31.2 ± 0.5°C, TTX: 28.3 ± 0.7°C; P < 0.01) and a significant increase in HR (control: 425.2 ± 12 beats/min, TTX: 502.1 ± 13 beats/min; P < 0.01). These results suggest that the TTX-induced hyperthermia was the result of both an impairment of heat loss and an elevation of heat production during exercise. We therefore propose the PO/AH as an important thermoregulatory site in the brain during exercise.
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Affiliation(s)
- Hiroshi Hasegawa
- Dept. of Human Physiology and Sportsmedicine, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
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Kurtz TW, Griffin KA, Bidani AK, Davisson RL, Hall JE. Recommendations for Blood Pressure Measurement in Humans and Experimental Animals. Arterioscler Thromb Vasc Biol 2005; 25:e22-33. [PMID: 15731483 DOI: 10.1161/01.atv.0000158419.98675.d7] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In experimental animals, as in humans, techniques for measuring blood pressure (BP) have improved considerably over the past decade. In this document, we present recommendations for measuring BP in experimental animals with the goal of helping investigators select optimal methods for BP monitoring in the research laboratory. The advantages and disadvantages of various BP measurement methods are discussed and specific recommendations are provided for selecting the optimal technique depending on the study objective. Although indirect techniques that permit only sporadic measurements of BP may be suitable for some purposes, methods for directly measuring BP are generally preferred because of their ability to monitor the highly dynamic nature of BP in a comprehensive fashion. Selection of the methods to be used should ultimately be guided by the study objectives to insure that the techniques chosen are appropriate for the experimental questions being explored.
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Kurtz TW, Griffin KA, Bidani AK, Davisson RL, Hall JE. Recommendations for Blood Pressure Measurement in Humans and Experimental Animals. Hypertension 2005; 45:299-310. [PMID: 15611363 DOI: 10.1161/01.hyp.0000150857.39919.cb] [Citation(s) in RCA: 225] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In experimental animals, as in humans, techniques for measuring blood pressure (BP) have improved considerably over the past decade. In this document, we present recommendations for measuring BP in experimental animals with the goal of helping investigators select optimal methods for BP monitoring in the research laboratory. The advantages and disadvantages of various BP measurement methods are discussed and specific recommendations are provided for selecting the optimal technique depending on the study objective. Although indirect techniques that permit only sporadic measurements of BP may be suitable for some purposes, methods for directly measuring BP are generally preferred because of their ability to monitor the highly dynamic nature of BP in a comprehensive fashion. Selection of the methods to be used should ultimately be guided by the study objectives to insure that the techniques chosen are appropriate for the experimental questions being explored.
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Swoap SJ, Overton JM, Garber G. Effect of ambient temperature on cardiovascular parameters in rats and mice: a comparative approach. Am J Physiol Regul Integr Comp Physiol 2004; 287:R391-6. [PMID: 15087284 DOI: 10.1152/ajpregu.00731.2003] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ambient air temperatures (T(a)) of <6 degrees C or >29 degrees C have been shown to induce large changes in arterial blood pressure and heart rate in homeotherms. The present study was designed to investigate whether small incremental changes in T(a), such as those found in typical laboratory settings, would have an impact on blood pressure and other cardiovascular parameters in mice and rats. We predicted that small decreases in T(a) would impact the cardiovascular parameters of mice more than rats due to the increased thermogenic demands resulting from a greater surface area-to-volume ratio in mice relative to rats. Cardiovascular parameters were measured with radiotelemetry in mice and rats that were housed in temperature-controlled environments. The animals were exposed to different T(a) every 72 h, beginning at 30 degrees C and incrementally decreasing by 4 degrees C at each time interval to 18 degrees C and then incrementally increasing back up to 30 degrees C. As T(a) decreased, mean blood pressure, heart rate, and pulse pressure increased significantly for both mice (1.6 mmHg/ degrees C, 14.4 beats.min(-1). degrees C(-1), and 0.8 mmHg/ degrees C, respectively) and rats (1.2 mmHg/ degrees C, 8.1 beats.min(-1). degrees C(-1), and 0.8 mmHg/ degrees C, respectively). Thus small changes in T(a) significantly impact the cardiovascular parameters of both rats and mice, with mice demonstrating a greater sensitivity to these T(a) changes.
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Affiliation(s)
- Steven J Swoap
- Department of Biology, Williams College, Williamstown, MA 01267, USA.
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Williams TD, Chambers JB, Henderson RP, Rashotte ME, Overton JM. Cardiovascular responses to caloric restriction and thermoneutrality in C57BL/6J mice. Am J Physiol Regul Integr Comp Physiol 2002; 282:R1459-67. [PMID: 11959690 DOI: 10.1152/ajpregu.00612.2001] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We utilized variations in caloric availability and ambient temperature (T(a)) to examine interrelationships between energy expenditure and cardiovascular function in mice. Male C57BL/6J mice (n = 6) were implanted with telemetry devices and housed in metabolic chambers for measurement of mean arterial pressure (MAP), heart rate (HR), O(2) consumption (VO(2)), and locomotor activity. Fasting (T(a) = 23 degrees C), initiated at the onset of the dark phase, resulted in large and transient depressions in MAP, HR, VO(2), and locomotor activity that occurred during hours 6-17, which suggests torporlike episodes. Food restriction (14 days, 60% of baseline intake) at T(a) = 23 degrees C resulted in progressive reductions in MAP and HR across days that were coupled with an increasing occurrence of episodic torporlike reductions in HR (<300 beats/min) and VO(2) (<1.0 ml/min). Exposure to thermoneutrality (T(a) = 30 degrees C, n = 6) reduced baseline light-period MAP (-14 +/- 2 mmHg) and HR (-184 +/- 12 beats/min). Caloric restriction at thermoneutrality produced further reductions in MAP and HR, but indications of torporlike episodes were absent. The results reveal that mice exhibit robust cardiovascular responses to both acute and chronic negative energy balance. Furthermore, we conclude that T(a) is a very important consideration when assessing cardiovascular function in mice.
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Affiliation(s)
- T D Williams
- Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, Florida 32306-4340, USA
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Overton JM, Williams TD, Chambers JB, Rashotte ME. Cardiovascular and metabolic responses to fasting and thermoneutrality are conserved in obese Zucker rats. Am J Physiol Regul Integr Comp Physiol 2001; 280:R1007-15. [PMID: 11247821 DOI: 10.1152/ajpregu.2001.280.4.r1007] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The primary purpose of the study was to test the hypothesis that reduced leptin signaling is necessary to elicit the cardiovascular and metabolic responses to fasting. Lean (Fa/?; normal leptin receptor; n = 7) and obese (fa/fa; mutated leptin receptor; n = 8) Zucker rats were instrumented with telemetry transmitters and housed in metabolic chambers at 23 degrees C (12:12-h light-dark cycle) for continuous (24 h) measurement of metabolic and cardiovascular variables. Before fasting, mean arterial pressure (MAP) was higher (MAP: obese = 103 +/- 3; lean = 94 +/- 1 mmHg), whereas oxygen consumption (VO(2): obese = 16.5 +/- 0.3; lean = 18.6 +/- 0.2 ml. min(-1). kg(-0.75)) was lower in obese Zucker rats compared with their lean controls. Two days of fasting had no effect on MAP in either lean or obese Zucker rats, whereas VO(2) (obese = -3.1 +/- 0.3; lean = -2.9 +/- 0.1 ml. min(-1). kg(-0.75)) and heart rate (HR: obese = -56 +/- 4; lean = -42 +/- 4 beats/min) were decreased markedly in both groups. Fasting increased HR variability both in lean (+1.8 +/- 0.4 ms) and obese (+2.6 +/- 0.3 ms) Zucker rats. After a 6-day period of ad libitum refeeding, when all parameters had returned to near baseline levels, the cardiovascular and metabolic responses to 2 days of thermoneutrality (ambient temperature 29 degrees C) were determined. Thermoneutrality reduced VO(2) (obese = -2.4 +/- 0.2; lean = -3.3 +/- 0.2 ml. min(-1). kg(-0.75)), HR (obese = -46 +/- 5; lean = -55 +/- 4 beats/min), and MAP (obese = -13 +/- 6; lean = -10 +/- 1 mmHg) similarly in lean and obese Zucker rats. The results indicate that the cardiovascular and metabolic responses to fasting and thermoneutrality are conserved in Zucker rats and suggest that intact leptin signaling may not be requisite for the metabolic and cardiovascular responses to reduced energy intake.
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Affiliation(s)
- J M Overton
- Departments of Nutrition, Food and Exercise Sciences and Program in Neuroscience, 236 Biomedical Research Facility, Florida State University, Tallahassee, FL 32306-4340, USA.
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