Effects of encapsulated niacin on evaporative heat loss and body temperature in moderately heat-stressed lactating Holstein cows

Male CBA/J mice were administered heat loads of 0–28 J X g-1 at specific absorption rates (SARs) of either 47 or 93 W X kg-1 by exposure to 2,450-MHz microwave radiation at an ambient temperature of 30 degrees C while evaporative heat loss (EHL) was continuously monitored with dew-point hygrometry. At an SAR of 47 W X kg-1 a threshold heat load of 10.5 J X g-1 had to be exceeded before EHL increased. An approximate doubling of SAR to 93 W X kg-1 reduced the threshold to 5.2 J X g-1. Above threshold the slopes of the regression lines were 1.15 and 0.929 for the low- and high-SAR groups, respectively. Thus the difference in threshold and not slope attributes to the significant increase in EHL when mice are exposed at a high SAR (P less than 0.02). In separate experiments a SAR of 47 W X kg-1 raised the deep body temperature of anesthetized mice at a rate of 0.026 degrees C X s-1, whereas 93 W X kg-1 raised temperature at 0.049 degrees C X s-1. Hence the sensitivity of the EHL mode of heat dissipation is directly proportional to the rate of heat absorption and to the rate of rise in body temperature. These data contradict the notion that mammals have control over whole-body heat exchange only (i.e., thermoregulation) but instead indicate that the EHL system is highly responsive to the rate of heat absorption (i.e., temperature regulation).

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Effect of 5-hydroxytryptamine and acetylcholine on the energy budget of chickens

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1980.239.1.r57 ◽

1980 ◽

Vol 239 (1) ◽

pp. R57-R61

Author(s):

P. E. Hillman ◽

N. R. Scott ◽

A. van Tienhoven

Keyword(s):

Physical Activity ◽

Heart Rate ◽

Body Temperature ◽

Heat Loss ◽

Energy Budget ◽

Heat Production ◽

Evaporative Heat Loss ◽

Neural Pathways ◽

Metabolic Heat ◽

Intraventricular Injections

Intraventricular injections of 5-hydroxytryptamine-HCl (258 nmol) or acetylcholine-HCl (550 nmol) in the chicken caused body temperature to rise at 35 degrees C ambient, a result of decreased evaporative heat loss due to bradypnea. At 10 and 20 degrees C ambient, neither drug affected body temperature. Although these drugs decreased physical activity or shivering or both at 10 and 20 degrees C, metabolic heat production was not depressed enough to alter body temperature significantly. Heart rate decreased simultaneously with decreased activity at 20 degrees C. This study is the first to inject 5-hydroxytryptamine as a salt of HCl, instead of creatinine sulfate, as is commonly used. It is suggested that some of the differences reported herein, compared to other studies, are due to the type of salt used. It is postulated that either 5-hydroxytryptamine or acetylcholine, rather than norepinephrine, may be an important neurotransmitter in the neural pathways for thermoregulation in chickens, even though their action on thermoregulation is minor compared with norepinephrine.

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Elevated CSF osmolality inhibits thermoregulatory heat loss responses

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1986.251.4.r749 ◽

1986 ◽

Vol 251 (4) ◽

pp. R749-R754 ◽

Cited By ~ 9

Author(s):

E. Turlejska ◽

M. A. Baker

Keyword(s):

Cerebrospinal Fluid ◽

Body Temperature ◽

Ambient Temperature ◽

Heat Loss ◽

Preoptic Area ◽

Brain Temperature ◽

High Ambient Temperature ◽

Evaporative Heat Loss ◽

Artificial Cerebrospinal Fluid ◽

Hot Environments

The effect of intracerebroventricular (icv) infusions of hypertonic NaCl or sucrose on thermoregulatory responses to heat was studied in conscious rabbits to test the idea that brain osmoreceptors are involved in the inhibition of evaporative heat loss and elevation of body temperature in dehydrated mammals at high ambient temperature (Ta). In rabbits hydrated ad lib and resting at a Ta of 33 degrees C, icv infusion (3.4 microliter/min) of hypertonic (1,500 mosm) NaCl or sucrose in artificial cerebrospinal fluid (ACSF) produced a significant reduction in respiratory frequency (f) and in ear skin temperature (Te) and a rise in brain temperature (preoptic area, Tpoa). icv infusion of ACSF alone or ACSF + NaCl at 500 and at 750 mosm had no effect on f or on Te or Tpoa. Infusion of NaCl + ACSF at 1,000 mosm reduced f but did not affect Te or Tpoa. In hydrated rabbits, icv infusion of 1,500 mosm NaCl abolished the rise in f and in Te elicited by POA heating at Ta of 25 degrees C. In dehydrated rabbits at 33 degrees C, f was below hydrated levels and icv infusion of water (6.8 microliter/min) produced a reversible elevation in f. These findings suggest that brain osmoreceptors can influence thermoregulation in hot environments.

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Influence of air humidity on the partition of heat exchanges of cattle

The Journal of Agricultural Science ◽

10.1017/s0021859600069148 ◽

1972 ◽

Vol 78 (2) ◽

pp. 303-307 ◽

Cited By ~ 22

Author(s):

J. A. McLean ◽

D. T. Calvert

Keyword(s):

Body Temperature ◽

Heat Loss ◽

Air Temperature ◽

Heat Production ◽

Total Heat ◽

Evaporative Heat Loss ◽

Air Humidity ◽

Total Heat Loss ◽

Air Temperatures ◽

Heat Exchanges

SUMMARYThe balance between heat production and heat loss and the partition of heat exchanges of cattle in relation to air humidity has been studied at two different air temperatures using a direct (gradient-layer) calorimeter.Increasing humidity at 35 °C air temperature caused no significant change in heat production or in the level of total heat loss finally attained, but body temperature and respiratory activity were both increased.Increasing humidity at 15 °C air temperature caused a small reduction in heat loss by evaporation but had no effect on sensible heat loss, body temperature or respiratory frequency.Heat loss by evaporation amounted to 18% of the total heat loss at 15 °C and to 84% at 35 °C.Heat loss by respiratory evaporation amounted to 54% of the total evaporative heat loss at 15 °C and to 38% at 35 °C.

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Cutaneous heat loss shortly after burn injury in children

Clinical Science ◽

10.1042/cs0830117 ◽

1992 ◽

Vol 83 (1) ◽

pp. 117-126 ◽

Cited By ~ 5

Author(s):

Charmaine Childs ◽

H. B. Stoner ◽

R. A. Little

Keyword(s):

Body Temperature ◽

Heat Loss ◽

Burn Injury ◽

Heat Content ◽

Total Heat ◽

Evaporative Heat Loss ◽

Healthy Children ◽

Total Heat Loss ◽

Control Subjects ◽

Injured Patients

1. Total heat loss and its components have been studied in cool (20°C) and warm (30°C) environments in 30 healthy children and 21 children who had been burned (10-17% body surface area) 0.5-29 h previously. 2. In healthy naked children at 20°C, the partition of total heat loss was: radiation, 64%; convection, 32%; evaporation, 4%. On transfer to the warm, total heat loss was reduced by approximately 50%, with disproportionate reductions in the contributions from radiation and convection being offset, to some extent, by an increase in evaporative heat loss. 3. In patients during the first 5.5 h after injury, the magnitude and pattern of heat loss at 20°C and 30°C were similar to those in control subjects and were unaffected by bandaging. 4. Ten to twenty-nine hours after injury, when the patients were bandaged and body temperature and heat content were significantly higher than in control subjects, radiant and convective heat losses were increased, but as evaporative heat loss tended to be reduced; total heat loss in the warm was unchanged. However, at this time at 20°C, total heat loss was reduced compared with healthy children at the same ambient temperature. 5. The findings of unchanged or reduced total heat loss and reduced evaporative heat loss in injured patients are interpreted as inappropriate responses to an increased body temperature and heat content in children after burn injury.

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Evaporative cooling and cutaneous surface temperature of Holstein cows in tropical conditions

Revista Brasileira de Zootecnia ◽

10.1590/s1516-35982011000500028 ◽

2011 ◽

Vol 40 (5) ◽

pp. 1143-1147 ◽

Cited By ~ 9

Author(s):

Roberto Gomes da Silva ◽

Alex Sandro Campos Maia

Keyword(s):

Heat Loss ◽

Coat Colour ◽

Holstein Cows ◽

Coefficient Of Determination ◽

Evaporative Heat Loss ◽

Exponential Relationship ◽

Body Regions ◽

Tropical Conditions ◽

Three Body ◽

Cutaneous Evaporation

The effects of skin temperature (T S) on the rate of heat loss by cutaneous evaporation (E S) in Holstein cows chronically exposed to sun, considering hair coat colour were studied. Sixteen purebred cows were measured for E S and T S at 01:00 p.m. after 6 hours of exposure to sun, on three body regions (flank, neck and gluteus) and considering dark and white spots separately. Sweating rate (S) and E S were measured by means of a ventilated capsule. Black skin areas presented mean S (138.9 ± 8.5 gm-2 h-1), E S (93.3 ± 5.7 Wm-2), and T S (33.1 ± 0.2°C) higher than those in the white areas (109.5 ± 9.7 gm-2h-1), 73.6 ± 6.5 Wm-2 and 32.6 ± 0.2°C, respectively). There is an exponential relationship among cutaneous temperature and cutaneous evaporation, which can be represented by the equation: E S = 31.5 + exp{(T S - 27.9)/2.19115}, with coefficient of determination r² = 0.68. Cutaneous evaporative heat loss remains almost constant around 48 Wm-2 until T S reaches nearly 31°C.

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Changes in serotonin contents in brain affect metabolic heat production of rabbits in cold

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1978.235.1.r41 ◽

1978 ◽

Vol 235 (1) ◽

pp. R41-R47

Author(s):

M. T. Lin ◽

I. H. Pang ◽

S. I. Chern ◽

W. Y. Chia

Keyword(s):

Blood Flow ◽

Amino Acid ◽

Heat Loss ◽

Acid Decarboxylase ◽

Evaporative Heat Loss ◽

Decarboxylase Inhibitor ◽

Ambient Temperatures ◽

Amino Acid Decarboxylase ◽

Metabolic Heat ◽

Normal Limits

Elevating serotonin (5-HT) contents in brain with 5-hydroxytryptophan (5-HTP) reduced rectal temperature (Tre) in rabbits after peripheral decarboxylase inhibition with the aromatic-L-amino-acid decarboxylase inhibitor R04-4602 at two ambient temperatures (Ta), 2 and 22 degrees C. The hypothermia was brought about by both an increase in respiratory evaporative heat loss (Eres) and a decrease in metabolic rate (MR) in the cold. At a Ta of 22 degrees C, the hypothermia was achieved solely due to an increase in heat loss. Depleting brain contents of 5-HT with intraventricular, 5,7-dihydroxytryptamine (5,7-DHT) produced an increased Eres and ear blood flow even at Ta of 2 degrees C. Also, MR increased at all but the Ta of 32 degrees C. However, depleting the central and peripheral contents of 5-HT with p-chlorophenylalanine (pCPA) produced lower MR accompanied by lower Eres in the cold compared to the untreated control. Both groups of pCPA-treated and 5,7-DHT-treated animals maintained their Tre within normal limits. The data suggest that changes in 5-HT content in brain affects the MR of rabbits in the cold. Elevating brain content of 5-HT tends to depress the MR response to cold, while depleting brain content of 5-HT tends to enhance the MR response to cold.

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Comparison of the effect of isopropyl alcohol and chlorhexidine solution rinses on body temperature of female cats undergoing sterilization surgery

Journal of Feline Medicine and Surgery ◽

10.1177/1098612x20979565 ◽

2021 ◽

pp. 1098612X2097956

Author(s):

Rachael E Kreisler ◽

Michelle L Douglas ◽

Karissa N Harder

Keyword(s):

Body Temperature ◽

Heat Loss ◽

Isopropyl Alcohol ◽

Body Condition Score ◽

High Volume ◽

Veterinary Students ◽

Reversal Agents ◽

Duration Of Surgery ◽

Chlorhexidine Solution ◽

Recovery Temperature

Objectives Isopropyl alcohol 70% as a rinse agent for chlorhexidine scrub has been shown to decrease body temperature more quickly than chlorhexidine solution in mice prepared aseptically prior to surgery. For this reason, some high-quality, high-volume (HQHV) surgical sterilization clinics use chlorhexidine solution rather than alcohol. We sought to determine if temperature upon entry to recovery, heat loss per kg and rate of temperature decline during surgery were different between cats rinsed with chlorhexidine solution vs 70% isopropyl alcohol following surgical scrub, and if there were significant predictors of recovery temperature. Methods Female cats admitted for surgery to trap–neuter–return (TNR) clinics at a veterinary college were assigned chlorhexidine solution or alcohol rinse agents via block randomization. Veterinary students and veterinarians performed spay surgeries using HQHV techniques. In recovery, heat support and reversal agents were available for cats with a low body temperature or that were slow to recover. Baseline values, outcome variables and duration of each stage (preparation, surgery, recovery) were assessed using Wilcoxon rank-sum and t-tests. Recovery temperature was evaluated using random effects multiple linear regression. Results The recovery temperature, heat loss per kg, heat loss per min, need for reversal and need for heat support in recovery were not significantly different between rinse groups. Weight <2.3 kg, body condition score <4, duration of surgery and postinduction temperature were predictors of recovery temperature. The rate of heat loss in the first 30 mins of surgery was slightly lower for cats in the alcohol rinse group and the recovery duration was shorter for cats weighing less <2.3 kg in the alcohol rinse group. Conclusions and relevance There were no clinically meaningful differences in body temperature between chlorhexidine and alcohol rinses. Both chlorhexidine solution and isopropyl alcohol 70% are appropriate rinse agents for aseptic preparation of feline spay surgeries.

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