Ventilatory and metabolic responses to cold and CO2 in intact and carotid body-denervated awake rats

1993 ◽  
Vol 75 (6) ◽  
pp. 2570-2579 ◽  
Author(s):  
H. Gautier ◽  
M. Bonora ◽  
H. C. Trinh
Keyword(s):  
Carotid Body ◽  
System Level ◽  
Nonshivering Thermogenesis ◽  
Ventilatory Control ◽  
Pco2 Level ◽  
Ambient Temperatures ◽  
The Central Nervous System ◽  
Central Actions ◽  
Colonic Temperature ◽  
Different Sources

We investigated in conscious rats the characteristics and modes of action of CO2 on thermoregulation and ventilatory control during cold stress. In a group of 10 rats studied intact and after carotid body denervation, measurements of metabolic rate (VO2), ventilation (V), shivering, and colonic temperature (Tc) were made at controlled ambient temperatures (Ta) of 25, 20, 15, 10, and 5 degrees C. Animals were exposed on different days to 1) normoxia, 2) normoxia and 4% CO2, 3) 12% hypoxia, or 4) 10.8% hypoxia and 4% CO2. The following results were obtained. 1) During CO2 exposure in normoxia or hypoxia, VO2 is increased at Ta of 25 degrees C and decreased for lower Ta. These effects are partly mediated by carotid body afferents. 2) Shivering and nonshivering thermogenesis and therefore Tc regulation are affected by CO2 exposure as shown by relationships between VO2-Tc and VO2-shivering intensity. 3) V is controlled by PO2 and PCO2 directly through their peripheral and central actions but also indirectly through their effects on VO2. Our conclusions are as follows. 1) Control of Tc is markedly dependent on PCO2 level. Carotid body afferents play a role, but direct central effects acting on the different sources of thermogenesis and possibly on thermolysis are most prominent. 2) As far as control of V is concerned, during hypercapnia in normoxia or hypoxia, several analogies may be formed between exposure to cold and muscular exercise, both of which increase VO2 and V, suggesting common integrative mechanisms at the central nervous system level.

Ventilatory and metabolic responses to cold and hypoxia in intact and carotid body-denervated rats

1992 ◽  
Vol 73 (3) ◽  
pp. 847-854 ◽  
Author(s):  
H. Gautier ◽  
M. Bonora
Keyword(s):  
Metabolic Rate ◽  
Cold Exposure ◽  
Carotid Body ◽  
Metabolic Responses ◽  
Nonshivering Thermogenesis ◽  
Ventilatory Control ◽  
Before And After ◽  
Colonic Temperature ◽  
Shivering Thermogenesis ◽  
Made In

The effects of hypoxia on thermoregulation and ventilatory control were studied in conscious rats before and after carotid denervation (CD). Measurements of metabolic rate (VO2), ventilation (V), shivering intensity (SI), and colonic temperature (Tc) were made in groups of eight rats subjected to three protocols. In protocols 1 and 2, at ambient temperature (Ta) of 25 and 5 degrees C, respectively, rats were exposed to normoxia and hypoxia [inspired O2 fraction (FIO2) 0.13–0.11]. In protocol 3, Ta was decreased from 25 to 5 degrees C in 30-min steps of 5 degrees C. Recordings were made in normoxia and hypoxia (FIO2 0.12). The results show that in both intact and CD rats 1) in normoxia, cold exposure increased VO2, V, and SI, and these increases were proportional to the decrease in Ta; 2) hypoxia induced only a transient decrease in SI, and, for a given Ta, VO2 was reduced whereas V and SI were increased; and 3) in CD rats, V increased less during cold exposure in both normoxia and hypoxia; VO2 and Tc were more depressed during hypoxia. It is concluded that 1) the interaction between Ta and FIO2 in the control of V is partly dependent on the carotid body afferents, 2) shivering thermogenesis may be transiently affected by hypoxia independently of the carotid body afferents, and 3) nonshivering thermogenesis may be directly inhibited by hypoxia, especially during cold exposure.

Adaptation to extreme ambient temperatures in cold-acclimated gerbils and mice

1987 ◽  
Vol 253 (1) ◽  
pp. R39-R45 ◽  
Author(s):  
S. Oufara ◽  
H. Barre ◽  
J. L. Rouanet ◽  
J. Chatonnet
Keyword(s):  
Evaporative Heat Loss ◽  
Electromyographic Activity ◽  
Arid Environments ◽  
Nonshivering Thermogenesis ◽  
Cold Night ◽  
Ambient Temperatures ◽  
In The Wild ◽  
Colonic Temperature ◽  
And Control ◽  
Thermoregulatory Reactions

To explain tolerance of heat and cold in gerbils (Gerbillus campestris) in their natural environment, a comparative study was made of thermoregulatory reactions in these animals and white mice (Mus musculus) of the same body mass exposed for 2-3 h to ambient temperatures (Ta) ranging from -23 to 40 degrees C. Metabolic rate (MR), evaporative heat loss (EHL), colonic temperature (Tb), and electromyographic activity (EMG) were measured. Nonshivering thermogenesis (NST) was also evaluated from the increase in MR after norepinephrine injection. In gerbils, tolerance of cold was higher than in mice; there was no fall in Tb in cold-acclimated (CA) and control (TN) gerbils after 3 h of exposure at -20 and -10 degrees C Ta, respectively; peak MR (PMR) reached five to six times resting MR (RMR) in gerbils and four to five times in mice. In gerbils, RMR was 35% below that of mice. In TN gerbils, EHL did not increase before 38 degrees C Ta; EHL increased at 26 degrees C in mice. In both animals, cold acclimation increased cold tolerance, PMR, RMR, and NST. Low RMR, high Tb, and mainly burrowing habits preserve gerbils from overheating and save water in hot and arid environments, and a conspicuous tolerance of cold allows them to live and forage in the wild during the cold night.

Ventilatory and metabolic responses to ambient hypoxia or hypercapnia in rats exposed to CO hypoxia

1997 ◽  
Vol 83 (1) ◽  
pp. 253-261 ◽  
Author(s):  
Henry Gautier ◽  
Cristina Murariu ◽  
Monique Bonora
Keyword(s):  
Carotid Body ◽  
Respiratory Activity ◽  
Metabolic Responses ◽  
Additive Effects ◽  
Ambient Temperatures ◽  
Conscious Rats ◽  
Ventilatory Responses ◽  
Before And After ◽  
Colonic Temperature ◽  
Ambient Hypoxia

Gautier, Henry, Cristina Murariu, and Monique Bonora.Ventilatory and metabolic responses to ambient hypoxia or hypercapnia in rats exposed to CO hypoxia. J. Appl. Physiol.83(1): 253–261, 1997.—We have investigated at ambient temperatures (Tam) of 25 and 5°C the effects of ambient hypoxia (Hxam; fractional inspired O2 = 0.14) and hypercapnia (fractional inspired CO2 = 0.04) on ventilation (V˙), O2 uptake (V˙o 2), and colonic temperature (Tc) in 12 conscious rats before and after carotid body denervation (CBD). The rats were concomitantly exposed to CO hypoxia (HxCO; fractional inspired CO = 0.03–0.05%), which decreases arterial O2 saturation by ∼25–40%. The results demonstrate the following. 1) At Tam of 5°C, in both intact and CBD rats,V˙/V˙o 2 is larger when Hxam or CO2 is associated with HxCO than with normoxia. At Tam of 25°C, this is also the case except for CO2 in CBD rats. 2) At Tam of 5°C, the changes inV˙o 2 and Tc seem to result from additive effects of the separate changes induced by Hxam, CO2, and HxCO. It is concluded that, in conscious rats, central hypoxia does not depress respiratory activity. On the contrary, particularly whenV˙o 2 is augmented during a cold stress, bothV˙/V˙o 2during HxCO and the ventilatory responses to Hxam and CO2 are increased. The mechanisms involved in this relative hyperventilation are likely to involve diencephalic integrative structures.

Effect of Bilateral Carotid-Body Resection on Ventilatory Control at Rest and during Exercise in Man

1971 ◽  
Vol 285 (20) ◽  
pp. 1105-1111 ◽  
Author(s):  
Robert Lugliani ◽  
Brian J. Whipp ◽  
Charles Seard ◽  
Karlman Wasserman
Keyword(s):  
Carotid Body ◽  
Ventilatory Control ◽  
Bilateral Carotid

Critical thermal maximum in mice

1976 ◽  
Vol 40 (5) ◽  
pp. 683-687 ◽  
Author(s):  
G. L. Wright
Keyword(s):  
Heat Stress ◽  
Cooling Capacity ◽  
Heating Time ◽  
Critical Thermal Maximum ◽  
Thermal Limit ◽  
Ambient Temperatures ◽  
Thermal Maximum ◽  
Righting Reflex ◽  
Colonic Temperature ◽  
Extended Exposure

The critical thermal maximum (the colonic temperature of heat-induced convulsion and righting reflex loss) and thermoregulatory response of male mice were examined following I, exposure to colonic temperature (Tco) 42 degrees C; II, a single exposure to the critical thermal maximum (Tco 44 degrees C); AND III, acclimation at ambient temperatures of 15 or 30 degrees C for 14 days. The critical thermal maximum (CTM) was greater in 30 degrees C acclimated mice than 15 degrees C acclimated mice but was unchanged in mice surviving exposure to Tco 42 degrees C or the CTM. The heating time to apparent breakdown of thermoregulation coincident with an explosive rise in the Tco during exposure to ambient temperature 40.8 degrees C was increased (100%) during the 48-h period following exposure to Tco 42 degrees. It appeared that mice exposed to severe, short-term heat stress (Tco 42 degrees) undergo a compensatory increase in their thermoregulatory cooling capacity with little or no change in the upper temperature tolerated. The animals did, however, exhibit the capability for adaptive adjustments of the upper thermal limit during extended exposure to the more prolonged and less severe environmental heat stress of acclimation at 30 degrees C.

Predominant role of peripheral chemoreceptors in the termination of apnea in maturing newborn lambs

1996 ◽  
Vol 80 (3) ◽  
pp. 892-898 ◽  
Author(s):  
C. Delacourt ◽  
E. Canet ◽  
M. A. Bureau
Keyword(s):  
Carotid Body ◽  
Pco2 Level ◽  
Peripheral Chemoreceptor ◽  
Arterial Pco2 ◽  
Postnatal Maturation ◽  
Body Function ◽  
Life Threatening ◽  
Prolonged Apnea ◽  
Arterial Po2

Apneas are very common and normal in newborns but may become life threatening if they are not terminated appropriately. The aim of this study in newborn lambs was to investigate the influence on apnea termination of postnatal maturation, peripheral chemoreceptor function, and hypoxia. Apneas were induced by passive hyperventilation at varying inspired O2 fraction levels. The apnea termination threshold PCO2 (PATTCO2) was defined as the arterial PCO2 value at the first breath after the apnea. Three groups of awake intubated lambs were studied: 1) intact lambs tested at both 1 and 15 days of life, 2) intact 1-day-old lambs with central tissue hypoxia induced by CO inhalation, and 3) 1-day-old lambs with carotid body denervation (CBD). In individual lambs and regardless of age and carotid body function, there was a PO2-PCO2 response curve that was a determinant for the termination of an apnea. PATTCO2 invariably increased when arterial PO2 increased, regardless of age. During hypoxia and normoxia, PATTCO2 was significantly lower in 15-day-old lambs compared with 1-day-old lambs. No difference was seen during hyperoxia. PATTCO2 values were shifted to higher levels after carotid body removal. Finally, hypoxia induced by either a low inspired O2 fraction or CO inhalation consistently failed to induce a depressive effect on the PATTCO2 even in CBD lambs. In conclusion, in awake newborn lambs, the PCO2 level for apnea termination changed with postnatal age, and carotid body function was essential in lowering PATTCO2, thus protecting the lambs against prolonged apnea. Furthermore, hypoxia consistently failed to depress the reinitiation of breathing after apnea, even in CBD lambs.

Inhibition of central actions of cytokines on fever and thermogenesis by lipocortin-1 involves CRF

1992 ◽  
Vol 263 (4) ◽  
pp. E632-E636 ◽  
Author(s):  
P. J. Strijbos ◽  
A. J. Hardwick ◽  
J. K. Relton ◽  
F. Carey ◽  
N. J. Rothwell
Keyword(s):  
Tumor Necrosis ◽  
Corticotropin Releasing Factor ◽  
Tnf Alpha ◽  
Eicosanoid Synthesis ◽  
Necrosis Factor Alpha ◽  
Recombinant Fragment ◽  
Factor Alpha ◽  
Central Actions ◽  
Colonic Temperature ◽  
Necrosis Factor

In the present studies, the mechanisms underlying the inhibitory actions of lipocortin-1 on the pyrogenic and thermogenic properties of cytokines were investigated. Central (icv) injection of corticotropin-releasing factor (CRF, 4.7 micrograms) or the recombinant cytokines interleukin (IL)-1 alpha (50 ng), IL-1 beta (5 ng), IL-6 (20 ng), IL-8 (20 ng), or tumor necrosis factor-alpha (TNF-alpha, 1 microgram) in conscious rats produced significant increases in resting oxygen consumption (VO2, 13-26%) and colonic temperature (0.7-1.6 degrees C) within 2 h postinjection. Administration (icv) of a recombinant fragment (NH2-terminus, 1-188 amino acids) of human lipocortin-1 (1.2 micrograms) produced small increases in VO2 (< 5%) and body temperature (< 0.3 degrees C). Pretreatment (-5 min) with lipocortin-1 significantly attenuated the thermogenic and pyrogenic effects of centrally injected IL-1 beta (80% inhibition), IL-6 (60%), IL-8 (80%), or CRF (60%). However, pretreatment with lipocortin-1 failed to modify the actions of IL-1 alpha or TNF-alpha. We have previously demonstrated that the pyrogenic and thermogenic effects of IL-1 beta, IL-6, and IL-8 are dependent on the central actions of CRF, whereas IL-1 alpha and TNF-alpha act independently of CRF. Fever and thermogenesis induced by all of these cytokines (with the exception of IL-8) can also be prevented by administration of a cyclooxygenase inhibitor. The data presented here suggest that the potent antipyretic effects of lipocortin-1 may result from inhibition of the release or actions of CRF rather than modulation of eicosanoid synthesis.

The Study of Comparative Characterization between SiC MOSFET and Si- IGBT for Power Module and Three-Phase SPWM Inverter

2020 ◽  
Vol 1004 ◽  
pp. 1045-1053
Author(s):  
Heng Lee ◽  
Chun Kai Liu ◽  
Tao Chih Chang
Keyword(s):  
Ambient Temperature ◽  
Junction Temperature ◽  
System Level ◽  
Switching Frequency ◽  
Power Module ◽  
Ambient Temperatures ◽  
Three Phase ◽  
Type Power ◽  
Three Phase Inverter ◽  
Better Than

This paper focuses on how to define and integrate the system level and power module level with optimal conditions in SiC and Si-IGBT. To investigate the above situation, we compare the performance of SiC and Si-IGBT in power module and system level at different ambient temperatures. At the same maximum junction temperature 150°C and ambient temperature at 25°C and 80°C, it found that SiC type electrical resistance, maximum endurable current, and voltage could be better than the IGBT type power module above 20%. On the other hand, the simulation of three-phase inverter at different switching frequency such as 10kHz, 15kHz, 20kHz, 30kHz and it had been observed that the power loss of SiC inverter are 78% less for 10kHz switching frequency; 82% less for switching frequency at 15kHz; 85% less for 20kHz of switching frequency; 89% less for switching frequency at 30kHz in the Si-IGBT three-phase SPWM inverter at ambient temperature 80°C.

scholarly journals EFFECT OF AMBIENT TEMPERATURE ON THERMAL RESPONSES TO DRUGS

1958 ◽  
Vol 36 (1) ◽  
pp. 1243-1249 ◽  
Author(s):  
Irving Shemano ◽  
Mark Nickerson
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Ambient Temperature ◽  
Ambient Temperatures ◽  
The Central Nervous System ◽  
Critical Ambient Temperature

Thermal responses to a variety of drugs have been investigated at various ambient temperatures, using unanesthetized rats, either lightly restrained or paralyzed with tubocurarine. The results indicate that ambient temperature is a major factor determining thermal responses to many drugs. Experiments on lightly restrained rats demonstrated that the critical ambient temperature, the temperature above which hyperthermia is evoked and below which hypothermia is produced, is about 30 °C (in the thermoneutral range) for Hydergine, ergotamine, LSD-25, and serotonin. The critical ambient temperature for chlorpromazine is approximately 36 °C, and that for 2,4-dinitrophenol, 20 °C. Reserpine produced a consistent hypothermia at 23 °C, but somewhat inconsistent effects at ambient temperatures above this up to 39 °C. Complete curarization abolished the hypothermic effects of all the above agents except chlorpromazine. The production of both hyperthermia and hypothermia by most of the drugs studied suggests that they influence temperature-regulating centers of the central nervous system.

The potentials of umbilical cord-derived mesenchymal stem cells in the treatment of multiple sclerosis

2019 ◽  
Vol 30 (8) ◽  
pp. 857-868 ◽  
Author(s):  
Ahmad Mehdipour ◽  
Ayyub Ebrahimi ◽  
Mohammad-Reza Shiri-Shahsavar ◽  
Jafar Soleimani-Rad ◽  
Leila Roshangar ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Cell Therapy ◽  
Umbilical Cord ◽  
Treatment Option ◽  
Adult Mesenchymal Stem Cells ◽  
The Central Nervous System ◽  
Promising Treatment ◽  
Different Sources

AbstractStem cell therapy has indicated a promising treatment capacity for tissue regeneration. Multiple sclerosis is an autoimmune-based chronic disease, in which the myelin sheath of the central nervous system is destructed. Scientists have not discovered any cure for multiple sclerosis, and most of the treatments are rather palliative. The pursuit of a versatile treatment option, therefore, seems essential. The immunoregulatory and non-chronic rejection characteristics of mesenchymal stem cells, as well as their homing properties, recommend them as a prospective treatment option for multiple sclerosis. Different sources of mesenchymal stem cells have distinct characteristics and functional properties; in this regard, choosing the most suitable cell therapy approach seems to be challenging. In this review, we will discuss umbilical cord/blood-derived mesenchymal stem cells, their identified exclusive properties compared to another adult mesenchymal stem cells, and the expectations of their potential roles in the treatment of multiple sclerosis.

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