Brown fat thermogenesis and cardiac rate regulation during cold challenge in infant rats

1997 ◽  
Vol 272 (4) ◽  
pp. R1308-R1313 ◽  
Author(s):  
M. S. Blumberg ◽  
G. Sokoloff ◽  
R. F. Kirby
Keyword(s):  
Heat Production ◽  
Cardiac Rate ◽  
Rat Pups ◽  
Infant Rats ◽  
Air Temperatures ◽  
Brown Adipose ◽  
Cold Challenge ◽  
Extreme Cold ◽  
Relationship Of ◽  
The Relationship

Infants rats depend on heat production by brown adipose tissue (BAT) during cold challenge. Although it has been suggested that BAT thermogenesis protects the heart in the cold, the relationship of BAT activation to cardiac rate has not been examined directly. In the first experiment, the cardiac rate of 2- and 7- to 8-day-old rat pups was monitored during moderate and extreme cold challenge. Pups at both ages maintained cardiac rate during moderate cold challenge while BAT thermogenesis was increasing. In contrast, cooling to air temperatures at which BAT thermogenesis could increase no further resulted in pronounced bradycardia. In the second experiment, ganglionic blockade was used to eliminate BAT heat production and autonomic control of the heart in 7- to 8-day olds. Blockade suppressed BAT thermogenesis in the cold and led to pronounced decreases in interscapular temperature and cardiac rate. These data suggest that cardiac rate in infant rats is modulated both by the autonomic nervous system and BAT thermogenesis.

Energy expenditure during stress ulcer formation in vulnerable rats

1989 ◽  
Vol 256 (2) ◽  
pp. R403-R407
Author(s):  
D. Greenberg ◽  
S. H. Ackerman
Keyword(s):  
Food Deprivation ◽  
Heat Production ◽  
Oxidative Metabolism ◽  
Experimental Models ◽  
Gastric Erosion ◽  
Ulcer Formation ◽  
O2 Consumption ◽  
Stress Ulcers ◽  
Rat Pups ◽  
Brown Adipose

Rat pups separated early from their mothers at day 15 become vulnerable to hypothermia and gastric erosion formation when food deprived and physically restrained on postnatal day 30 (S.H. Ackerman, M. A. Hofer, and H. Weiner, Science Wash. DC. 201: 373-376, 1978, and Gastroenterology 75: 649-654, 1978). We tested the hypothesis that this hypothermia is associated with a decrease in oxidative metabolism. We measured O2 consumption of 30-day-old rat pups that had been previously separated at either day 15 (15w) or day 21 (21w). When food was available, 15w rats used as much O2 as 21w rats. When rats were food deprived or food deprived and restrained, 15w rats used significantly less O2 than 21w rats, implying less heat production. We hypothesized that this decrease in heat production during food deprivation and/or restraint was due to impaired thermogenesis resulting from inadequate release of endogenous norepinephrine (NE), which is a stimulant of brown adipose tissue- (BAT) mediated thermogenesis. To test this hypothesis we administered exogenous NE to 15w to 21w rats. Exogenous NE failed to increase O2 consumption in 21w or 15w rats when injected during either food deprivation or restraint. We concluded that 30-day-old 15w rats have decreased oxidative metabolism during food deprivation and restraint and therefore become hypothermic. This decreased oxidative metabolism does not appear to be attributable to insufficient endogenous NE, since it is not reversed by the addition of exogenous NE. We suggest that a decrease in oxidative metabolism may explain susceptibility to stress ulcers in a number of previously reported experimental models.

Further evidence that BAT thermogenesis modulates cardiac rate in infant rats

1998 ◽  
Vol 274 (6) ◽  
pp. R1712-R1717 ◽  
Author(s):  
Greta Sokoloff ◽  
Robert F. Kirby ◽  
Mark S. Blumberg
Keyword(s):  
Adipose Tissue ◽  
Protective Role ◽  
Cardiac Rate ◽  
Warm Environment ◽  
Infant Rats ◽  
Brown Adipose ◽  
Warm Blood ◽  
Old Rats ◽  
Focal Cooling ◽  
Interscapular Region

Previous research in infant rats suggested that brown adipose tissue (BAT), by providing warm blood to the heart during moderate cold exposure, protects cardiac rate. This protective role for BAT thermogenesis was examined further in the present study. In experiment 1, 1-wk-old rats in a warm environment were pretreated with saline or chlorisondamine (a ganglionic blocker), and then BAT thermogenesis was stimulated by injection with the β3-agonist CL-316243. In experiment 2, pups were pretreated with chlorisondamine and injected with CL-316243, and after BAT thermogenesis was stimulated the interscapular region of the pups was cooled externally with a thermode. In both experiments, cardiac rate, oxygen consumption, and physiological temperatures were monitored. Activation of BAT thermogenesis substantially increased cardiac rate in saline- and chlorisondamine-treated pups, and focal cooling of the interscapular region was sufficient to lower cardiac rate. The results of these studies support the hypothesis that BAT thermogenesis contributes directly to the modulation of cardiac rate.

The relationship of the subarachnoid injection of blood and blood fractions with cardiac rate change and arrhythmias

1994 ◽  
Vol 127 (2) ◽  
pp. 134-142 ◽  
Author(s):  
Nicholas Y. Lorenzo ◽  
Alvin M. Earle ◽  
Lisa L. Peterson ◽  
Gordon L. Todd ◽  
Lyal G. Leibrock
Keyword(s):  
Rate Change ◽  
Cardiac Rate ◽  
Subarachnoid Injection ◽  
Relationship Of ◽  
The Relationship

scholarly journals Characteristics of snow gliding on rock

1994 ◽  
Vol 19 ◽  
pp. 97-103 ◽  
Author(s):  
D.M Mcclung ◽  
Simon Walker ◽  
W. Gollen
Keyword(s):  
Constitutive Relations ◽  
Field Measurements ◽  
Air Temperatures ◽  
Rock Interface ◽  
Temporal And Spatial ◽  
Temporal And Spatial Characteristics ◽  
Snowpack Properties ◽  
Relationship Of ◽  
The Relationship ◽  
Snow Gliding

Field measurements were made of snow gliding on steep, smooth rock slabs. Supporting dala included snowpack properties, snow rock interface temperatures, air temperatures and precipitation. In this paper, the temporal and spatial dependence of gliding is discussed from two seasons of measurements. The results showed that the basic temporal and spatial characteristics repeated from year to year at the site. The relationship of the measurements to snow-gliding constitutive relations and applications is briefly discussed.

THE RELATIONSHIP OF AMBIENT AIR TEMPERATURES TO PREMATURE FLOWERING OF FLUE-CURED TOBACCO

1987 ◽  
Vol 67 (4) ◽  
pp. 1231-1234 ◽  
Author(s):  
MARK J. KING
Keyword(s):  
Nicotiana Tabacum ◽  
Low Temperature ◽  
Positive Relationship ◽  
Ambient Air ◽  
Total Degree ◽  
Air Temperatures ◽  
Nicotiana Tabacum L ◽  
Relationship Of ◽  
The Relationship

Exposure of tobacco (Nicotiana tabacum L.) seedlings to low ambient air temperatures during the 3 weeks prior to transplanting resulted in premature flowering. The percent premature flowering observed varied with the location of the experiment, the year, and the total degree units of temperature below 20 °C. A positive relationship between accumulated hourly temperatures below 20 °C and percent premature flowering was observed over four years at two locations.Key words: low temperature, premature flowering

The relationship between the rate of heat production and the level of milk production in a subtropical climate

1963 ◽  
Vol 14 (6) ◽  
pp. 874 ◽  
Author(s):  
A Berman ◽  
S Amir ◽  
R Volcani
Keyword(s):  
Heat Production ◽  
Feed Intake ◽  
Open Circuit ◽  
Subtropical Climate ◽  
Air Temperatures ◽  
Hourly Rate ◽  
Heat Increment ◽  
Heat Requirements ◽  
Ad Libitum ◽  
The Relationship

Heat production as determined by the open circuit mask method, thermoregulatory responses, fat-corrected milk (F.C.M.) yield, and feed intake were recorded in two groups of 11 Israeli-Holstein cows each from the seventh day after calving up to 104 days of lactation. One group was fed according to the Fredricksen standard and the other group ad libitum, its feed intake being 125% of the Fredricksen standard. The experiment was carried out from January to mid July. No apparent heat increment of lactation was observed in the group fed according to the Fredricksen standard. A highly significant heat increment was found (10.3 kcal/hr/kg F.C.M.) at lower air temperatures (16–22°C) in the group fed ad libitum, while at higher air temperatures (23–28°C) a smaller, non-significant heat increment (5.4 kcal/hr/kg F.C.M.) was found. The hourly rate of heat production, the rectal temperature, respiration rate, respiratory volume, and respiratory vaporization changed only by small non-significant amounts with increasing temperatures. From these data it is inferred that heat production did not increase above heat requirements, except for the group fed ad libitum during the period at lower temperatures. This is explained by an increase in the critical temperature of the animals through a gradual adaptation to the summer conditions. This adaptation involves a decreased peripheral insulation by the summer coat and a lower basal metabolic rate. It is , suggested that these adaptational processes occurring in nature should be considered in studies on heat increments of feeding and of lactation.

Sign in / Sign up

Export Citation Format

Share Document