Changes in body temperature of rats acclimated to heat with different acclimation schedules

1989 ◽  
Vol 67 (5) ◽  
pp. 2154-2157 ◽  
Author(s):  
O. Shido ◽  
Y. Yoneda ◽  
T. Nagasaka
Keyword(s):  
Wistar Rats ◽  
Heat Exposure ◽  
Heat Acclimation ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Hypothalamic Temperature ◽  
Male Wistar Rats ◽  
The Mean ◽  
Low Levels

Male Wistar rats, initially maintained at an ambient temperature (Ta) of 23.8 degrees C, were subjected to one of seven different heat acclimation schedules under a 12:12-h light-dark cycle (lights on at 0600 h). Two groups of rats were exposed to Ta of 32.4 degrees C all day for 5 (HC5) or 10 (HC10) days. The other four groups were exposed to Ta of 32.8 degrees C for 5 h/day during the last half of the dark phase for 5 (NI5) or 10 (NI10) consecutive days or during the last half of the light phase for 5 (DI5) or 10 (DI10) consecutive days. Control rats (C) were kept at 23.8 degrees C throughout the experiment. Hypothalamic temperature (Thy) was measured every 5 min with a chronically implanted thermocouple from 1 day before the beginning to 2 days after the end of the heat acclimation periods. During the heat acclimation periods, daily mean Thy rose significantly in HC5 and HC10 rats but decreased significantly in NI5 and NI10 rats. Daily mean Thy did not change in C, DI5, and DI10 rats. Thy in HC10 rats sharply decreased at the end of the heat acclimation periods and remained at low levels for approximately 3 h. On the 2nd postacclimation day, however, mean Thy returned and remained at a significantly higher level. In NI10 rats, the mean Thy in the postacclimation period was significantly lower than the preacclimation values. No such changes in mean Thy were observed in DI10 rats. Five-days of heat exposure had little effect on the postacclimation Thy.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Central Relaxin-3 Administration Causes Hyperphagia in Male Wistar Rats

Endocrinology ◽  
2005 ◽  
Vol 146 (8) ◽  
pp. 3295-3300 ◽  
Author(s):  
B. M. C. McGowan ◽  
S. A. Stanley ◽  
K. L. Smith ◽  
N. E. White ◽  
M. M. Connolly ◽  
...  
Keyword(s):  
Food Intake ◽  
Wistar Rats ◽  
Dark Phase ◽  
Central Administration ◽  
Light Phase ◽  
Male Wistar Rats ◽  
The Central Nervous System ◽  
Intracerebroventricular Injections ◽  
Relaxin 2 ◽  
G Protein Coupled

Abstract Relaxin-3 (INSL-7) is a recently discovered member of the insulin superfamily. Relaxin-3 mRNA is expressed in the nucleus incertus of the brainstem, which has projections to the hypothalamus. Relaxin-3 binds with high affinity to the LGR7 receptor and to the previously orphan G protein-coupled receptor GPCR135. GPCR135 mRNA is expressed predominantly in the central nervous system, particularly in the paraventricular nucleus (PVN). The presence of relaxin-3 and these receptors in the PVN led us to investigate the effect of central administration of relaxin-3 on food intake in male Wistar rats. The receptor involved in mediating these effects was also investigated. Intracerebroventricular injections of human relaxin-3 (H3) to satiated rats significantly increased food intake 1 h post administration in the early light phase [0.96 ± 0.16 g (vehicle) vs. 1.81 ± 0.21 g (180 pmol H3), P < 0.05] and the early dark phase [2.95 ± 0.45 g (vehicle) vs. 4.39 ± 0.39 g (180 pmol H3), P < 0.05]. Intra-PVN H3 administration significantly increased 1-h food intake in satiated rats in the early light phase [0.34 ± 0.16 g (vehicle) vs. 1.23 ± 0.30 g (18 pmol H3), P < 0.05] and the early dark phase [4.43 ± 0.32 g (vehicle) vs. 6.57 ± 0.42 g (18 pmol H3), P < 0.05]. Feeding behavior increased after intra-PVN H3. Equimolar doses of human relaxin-2, which binds the LGR7 receptor but not GPCR135, did not increase feeding. Hypothalamic neuropeptide Y, proopiomelanocortin, or agouti-related peptide mRNA expression did not change after acute intracerebroventricular H3. These results suggest a novel role for relaxin-3 in appetite regulation.

scholarly journals Melatonin MT1 and MT2 Receptors Exhibit Distinct Effects in the Modulation of Body Temperature across the Light/Dark Cycle

2019 ◽  
Vol 20 (10) ◽  
pp. 2452 ◽  
Author(s):  
Martha López-Canul ◽  
Seung Hyun Min ◽  
Luca Posa ◽  
Danilo De Gregorio ◽  
Annalida Bedini ◽  
...  
Keyword(s):  
Body Temperature ◽  
Receptor Antagonist ◽  
Partial Agonist ◽  
Receptor Subtypes ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Simultaneous Activation ◽  
Type 3 ◽  
G Protein Coupled

Melatonin (MLT) is a neurohormone that regulates many physiological functions including sleep, pain, thermoregulation, and circadian rhythms. MLT acts mainly through two G-protein-coupled receptors named MT1 and MT2, but also through an MLT type-3 receptor (MT3). However, the role of MLT receptor subtypes in thermoregulation is still unknown. We have thus investigated the effects of selective and non-selective MLT receptor agonists/antagonists on body temperature (Tb) in rats across the 12/12-h light–dark cycle. Rectal temperature was measured every 15 min from 4:00 a.m. to 9:30 a.m. and from 4:00 p.m. to 9:30 p.m., following subcutaneous injection of each compound at either 5:00 a.m. or 5:00 p.m. MLT (40 mg/kg) had no effect when injected at 5 a.m., whereas it decreased Tb during the light phase only when injected at 5:00 p.m. This effect was blocked by the selective MT2 receptor antagonist 4P-PDOT and the non-selective MT1/MT2 receptor antagonist, luzindole, but not by the α1/MT3 receptors antagonist prazosin. However, unlike MLT, neither the selective MT1 receptor partial agonist UCM871 (14 mg/kg) nor the selective MT2 partial agonist UCM924 (40 mg/kg) altered Tb during the light phase. In contrast, UCM871 injected at 5:00 p.m. increased Tb at the beginning of the dark phase, whereas UCM924 injected at 5:00 a.m. decreased Tb at the end of the dark phase. These effects were blocked by luzindole and 4P-PDOT, respectively. The MT3 receptor agonist GR135531 (10 mg/kg) did not affect Tb. These data suggest that the simultaneous activation of both MT1 and MT2 receptors is necessary to regulate Tb during the light phase, whereas in a complex but yet unknown manner, they regulate Tb differently during the dark phase. Overall, MT1 and MT2 receptors display complementary but also distinct roles in modulating circadian fluctuations of Tb.

Adrenal corticoids in hamsters: role in circadian timing

1985 ◽  
Vol 248 (4) ◽  
pp. R434-R438 ◽  
Author(s):  
H. E. Albers ◽  
L. Yogev ◽  
R. B. Todd ◽  
B. D. Goldman
Keyword(s):  
Wheel Running ◽  
Sampling Period ◽  
Dark Phase ◽  
Cortisol Secretion ◽  
Experimental Protocol ◽  
Light Phase ◽  
Dark Cycle ◽  
Physiological Control ◽  
Circadian Organization

The 24-h patterns of circulating cortisol and corticosterone were determined in male hamsters housed under a 14:10 light-dark cycle. Corticoid levels varied significantly over the 24-h sampling period with peak levels of both hormones occurring near the onset of the daily dark phase. The ratio of cortisol to corticosterone changed dramatically during the day. Corticosterone levels were significantly higher than cortisol during the early part of the light phase; however, cortisol levels became significantly higher than corticosterone when both hormones began their daily rise. To examine whether the circadian rhythm of cortisol secretion could be involved in the physiological control of hamster circadian organization, cortisol was infused at approximately physiological levels into adrenalectomized hamsters either continuously or in a 24-h rhythm. No significant differences were observed in the timing of circadian wheel-running rhythms in hamsters housed in LD 16:8, LD 14:10, or LL when cortisol was infused continuously, in a 24-h rhythm that mimicked the cortisol rhythm of intact hamsters, or in a 24-h rhythm several hours out of phase with the rhythm of intact hamsters. Provision of cortisol in a 24-h rhythm appeared to promote the survival of adrenalectomized hamsters since hamsters receiving a 24-h pattern of cortisol survived the experimental protocol significantly longer than those receiving the same dose of cortisol continuously.

Seven days of hot water heat acclimation does not modulate the change in heart rate variability during passive heat exposure

2020 ◽  
Author(s):  
Philippe Gendron ◽  
Hugo Gravel ◽  
Hadiatou Barry ◽  
Daniel Gagnon
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
High Frequency ◽  
Water Immersion ◽  
Heat Exposure ◽  
Thermal Strain ◽  
Heat Acclimation ◽  
Hot Water ◽  
Frequency Range ◽  
The Mean

We examined if the change in heart rate variability (HRV) during passive heat exposure is modified by hot water heat acclimation (HA). Sixteen healthy adults (28 ± 5 years, 5 females/11 males) underwent heat exposure in a water-perfused suit, pre and post 7 days of HA (60 minutes at rectal temperature ≥38.6°C). During passive heat exposure, heart rate (HR), the standard deviation of NN intervals (SDNN), the square root of the mean squared differences of successive NN intervals (RMSSD) and the power in the high frequency range (HF) were measured. No difference in HR (P=0.22), SDNN (P=0.87), RMSSD (P=0.79) and HF (P=0.23) was observed at baseline. The increase in HR (pre-HA: 43 ± 10, post-HA: 42 ± 9 bpm, P=0.57) and the decrease of SDNN (pre-HA: -54.1 ± 41.0, post-HA: -52.2 ± 36.8 ms, P=0.85), RMSSD (pre-HA: -70.8 ± 49.5, post-HA: -72.7 ± 50.4 ms, P=0.91) and HF (pre-HA: -28.0 ± 14.5, post-HA: -23.2 ± 17.1%, P=0.27) were not different between experimental visits at fixed increases in esophageal temperature. These results suggest that 7 consecutive days of hot water HA does not modify the change in HRV indices during passive heat exposure. Novelty bullets: - It remains unclear if heat acclimation alters the change in heart rate variability that occurs during passive heat exposure. - At matched levels of thermal strain, 7 consecutive days of hot water immersion did not modulate the change in indices of heart rate variability during passive heat exposure.

Diurnal potassium excretory cycles in the rat

1986 ◽  
Vol 250 (5) ◽  
pp. F930-F941 ◽  
Author(s):  
L. Rabinowitz ◽  
C. J. Wydner ◽  
K. M. Smith ◽  
H. Yamauchi
Keyword(s):  
Extracellular Fluid ◽  
Potassium Content ◽  
Extracellular Potassium ◽  
Dark Phase ◽  
Adrenal Steroids ◽  
Light Phase ◽  
High Potassium ◽  
Potassium Intake ◽  
Low Levels ◽  
Adrenalectomized Rats

Diurnal potassium cycles (DPC) were measured in unanesthetized undisturbed rats fed a liquid diet and maintained in a 12-h light-dark environment. A fourfold step increase in diet potassium content increased DPC amplitude without altering phase. After presentation of the high-potassium diet, the initial adaptive increase in excretion occurred within 1.5 h (diet given during dark phase) and within 6 h (diet given during light phase). On a day when food was withheld (no potassium intake), DPC were present but with a lowered amplitude. The amount of potassium excreted on a fasting day exceeded gut and extracellular fluid potassium content and was only modestly increased when rats were previously fed a high-potassium diet. In adrenalectomized rats that received no steroid replacement or received constant infusions of low levels of aldosterone, dexamethasone, or aldosterone plus dexamethasone, potassium balance and DPC were normal. It is concluded that the amplitude of DPC in the rat is determined in part by the availability of potassium from both intracellular and extracellular potassium pools; mechanisms independent of potassium intake can generate the DPC; and the presence or the cyclic secretion of adrenal steroids is not necessary for the generation of DPC in the rat.

scholarly journals The effect of heat treatment and particle size of bran on mineral absorption in rats

1982 ◽  
Vol 48 (3) ◽  
pp. 467-475 ◽  
Author(s):  
Andrea Caprez ◽  
Susan J. Fairweather-Tait
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Isotope Dilution ◽  
Wistar Rats ◽  
Specific Radioactivity ◽  
Young Male ◽  
Breakfast Cereal ◽  
Synthetic Diet ◽  
Male Wistar Rats ◽  
The Mean

1. The effect of heat treatment of bran on true zinc absorption was measured using an isotope-dilution technique. A bran-based breakfast cereal (heated to 204° for 40 min during manufacture) was incorporated into a semi-synthetic diet at a level of 180 g/kg, A parallel diet was formulated containing an identical weight of untreated bran from the same source plus other ingredients used to make the cereal.2. Young male Wistar rats (mean weight 80 g) were injected intramuscularly with 65Zn to label body Zn. They were given the heat-treated- and untreated-bran diets for 9 d. During the last 6 d of this period Zn intakes and faecal and urinary Zn were measured in order to calculate apparent Zn retention. True Zn retention was measured by taking into account losses of Zn of endogenous origin (labelled with 65Zn), by measuring faecal and urinary 65Zn taking the mean specific radioactivity of Zn in kidneys and upper small intestine to represent specific radioactivity of endogenous origin.3. Heat treatment of bran removed approximately one-third of the phytate, but this was not enough to improve Zn absorption from the diet. True Zn retention measured by isotope dilution was significantly higher (P < 0.02) than apparent Zn retention measured bv the conventional balance technique.4. The hypothesis that a reduction in particle size of bran would improve mineral availability was tested by feeding coarse and milled bran (100 g/kg diet) in a semi-synthetic diet to rats and measuring true Fe and apparent Zn absorptions. The importance of phytate was also investigated by feedino a diet containing dephytinized bran.5. Male Wistar rats (mean weight 172 g) were given diets containing coarse, milled or dephytinized bran for 9 d. Fe and Zn intakes were measured and faeces and urine collected for Fe and Zn analysis.6. The mean (±SE) particle size of the bran was reduced on milling from 3.5 (± 1.8) to 0.2–0.5 mm. There were no differences in the fraction of Fe retained between the three groups. Particle size had a small effect on Zn retention which was marginally higher in rats on the milled-bran diet (0.126 (± 0.023)) than in those on the coarse-bran diet (0.087 (± 0.012)). Total removal of phytate had a greater effect and apparent Zn retention from the dephytinized-bran diet was significantly higher (0.182 (±0.027), P < 0.01).

scholarly journals A new experimental model of cigarette smoke-induced emphysema in Wistar rats

2014 ◽  
Vol 40 (1) ◽  
pp. 46-54 ◽  
Author(s):  
Rodrigo de las Heras Kozma ◽  
Edson Marcelino Alves ◽  
Valter Abraao Barbosa-de-Oliveira ◽  
Fernanda Degobbi Tenorio Quirino dos Santos Lopes ◽  
Renan Cenize Guardia ◽  
...  
Keyword(s):  
Lung Function ◽  
Cigarette Smoke ◽  
Murine Model ◽  
Wistar Rats ◽  
Control Group ◽  
Therapeutic Approaches ◽  
Viable Option ◽  
Male Wistar Rats ◽  
Mean Linear Intercept ◽  
The Mean

OBJECTIVE: To describe a new murine model of cigarette smoke-induced emphysema. METHODS: Twenty-four male Wistar rats were divided into two groups: the cigarette smoke group, comprising 12 rats exposed to smoke from 12 commercial filter cigarettes three times a day (a total of 36 cigarettes per day) every day for 30 weeks; and the control group, comprising 12 rats exposed to room air three times a day every day for 30 weeks. Lung function was assessed by mechanical ventilation, and emphysema was morphometrically assessed by measurement of the mean linear intercept (Lm). RESULTS: The mean weight gain was significantly (approximately ten times) lower in the cigarette smoke group than in the control group. The Lm was 25.0% higher in the cigarette smoke group. There was a trend toward worsening of lung function parameters in the cigarette smoke group. CONCLUSIONS: The new murine model of cigarette smoke-induced emphysema and the methodology employed in the present study are effective and reproducible, representing a promising and economically viable option for use in studies investigating the pathophysiology of and therapeutic approaches to COPD.

Zur Analyse des Zeitsinnes bei Periplaneta americana

1959 ◽  
Vol 14 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Erwin Bünning
Keyword(s):  
Diurnal Cycle ◽  
Low Temperatures ◽  
Periplaneta Americana ◽  
Internal Clock ◽  
The Other ◽  
Dark Phase ◽  
Half Cycle ◽  
Light Phase ◽  
Dark Cycle ◽  
Running Activity

The running activity was used as a measure of the course of the endogenous diurnal periodicity in Periplaneta americana. The influence of low temperatures (+5°, +3°, -2°), which acted on the diurnal cycle at different times was tested. In one of the two half cycles the delay of the internal clock due to the chilling was smaller or equal to the duration of the chilling. During this phase, at least at temperatures greater than zero, a minimum time of chilling was necessary in order to demonstrate the delay clearly. In the other half cycle the delay is greater than the duration of the chilling.It is concluded that oscillations of relaxation are the basis of these phenomena. The phase of tension requires a minimum temperature. Below this minimum a gradual relaxation occurs. The phase of relaxation continues at low temperatures, but after some time it is gradually delayed.The normal 24-hour light-dark cycle regulates these oscillations in such a way that the phase of tension begins in the second half of the light phase and it attains its maximum in the first part of the dark phase.

Pre-existing inflammatory state compromises heat tolerance in rats exposed to heat stress

2007 ◽  
Vol 292 (1) ◽  
pp. R186-R194 ◽  
Author(s):  
Chin Leong Lim ◽  
Gary Wilson ◽  
Lindsay Brown ◽  
Jeff S. Coombes ◽  
Laurel T. Mackinnon
Keyword(s):  
Heat Stress ◽  
Heat Tolerance ◽  
Tissue Damage ◽  
Wistar Rats ◽  
Heat Stroke ◽  
Heat Exposure ◽  
The Core ◽  
Male Wistar Rats ◽  
Inflammatory State ◽  
Severe Heat Stress

This study investigated the roles of endotoxemia and heat-induced tissue damage in the pathology of heat stroke. In groups of eight, male Wistar rats were treated with heat exposure only (HE), or heat exposure with turpentine (T+HE), dexamethasone (D+HE), and turpentine and dexamethasone combined (TD+HE). The rats remained sedated for 2 h after receiving the respective treatments, followed by heat exposure until the core temperature (Tc) was 42°C for 15 min; control rats received turpentine (T), dexamethasone (D), and turpentine and dexamethasone (TD) without heat stress. Blood samples were collected before treatment ( baseline I), after 2 h of passive rest ( baseline II), at Tc 40°C (T40), and 15 min after achieving Tc 42°C (T42). No rats died in the nonheat-stressed groups. Survival rate was lowest in the TD+HE rats (37.5%), followed by the HE (62.5%), T+HE (75%), and D+HE (100%) rats ( P < 0.05). The duration of survival at T42°C was shortest in the TD+HE rats (9.9 ± 6.2 min) ( P < 0.01), followed by the T+HE (11.3 ± 6.1 min) and the HE (12.2 ± 4 min) ( P < 0.05) rats. The increase in plasma IL-6 concentrations was highest in the T+HE (352%) and HE (178%) rats ( P < 0.05). D+HE treatment suppressed the increases in plasma aspartate transaminase, alanine aminotransferase, and IL-6 and LPS concentrations during severe heat stress. Heat stroke can be triggered by endotoxemia or heat-induced tissue damage, and preexisting inflammation compromises heat tolerance, whereas blocking endotoxemia increases heat tolerance.

scholarly journals THE EFFECT OF SEMBUNG LEAF EXTRACT (BLUMEA BALSAMIFERA) ON THE NUMBER AND DIAMETER OF RATS LEYDIG CELLS INDUCED BY HIGH-FAT DIET

2021 ◽  
Vol 21 (no 1) ◽  
Author(s):  
Gede Widhiantara ◽  
Anak Agung Ayu Putri Permatasari ◽  
Putu Angga Wiradana
Keyword(s):  
Treatment Group ◽  
Leydig Cells ◽  
Wistar Rats ◽  
Leaf Extract ◽  
Control Group ◽  
Control Group Design ◽  
Core Diameter ◽  
Post Test ◽  
Male Wistar Rats ◽  
The Mean

This study aims to determine the morphology of Leydig cells in hyperlipidemic wistar rats after having administered with sembung (Blumea balsamifera) extract orally. This study utilised a randomized post-test only control group design. The sample in this study were 16 adult male wistar rats (Rattus novergicus) aged 3-4 months with a body weight of 150-200 grams, which were equally and randomly divided into two groups, namely control group (hyperlipidaemia and sterile aquadest) and treatment group (hyperlipidaemia and sembung leaf extract). Hyperlipidaemia was induced with lard administration for 50 days. Data were analysed statistically using the Independent t-test. The results showed that the number of Leydig cells in the treatment group was higher than the control group with 68.13 ± 1.89 and 55.63 ± 1.92 cells respectively (P <0.05). In addition, the mean Leydig cell core diameter of the control group, 5.00 ± 0.34 µm, was smaller compared to the treatment group which was 5.80 ± 0.20 µm (P <0.05). It can be inferred that sembung leaf extract provides a protective effect against damage to Leydig cells due to hyperlipidaemia.

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