摘要:

Thirty-four men were exposed to 8 °C for 2 h. Their reactions were studied to indicate how physiological relationships change during exposure to cold. Measurements of various body temperatures, MST, MBT, body heat content (BHC),, heat production, and heart rate (HR) were made before the onset of and periodically during cold exposure. Various skin temperatures fell to different levels while rectal temperature rose slightly, then fell 0.3 °C by the end of the exposure. BHC declined by 6%,nearly doubled,and heat production increased by 66 and 75% respectively, and HR changed little during cold exposure. Relationships which changed most significantly during cold exposure were those between MST and rectal temperature, certain skin temperatures and rectal temperature,(also heat production) and BHC,and rectal temperature, and finally, those between every body temperature and the age of the subjects. Relationships which also changed were those between finger and toe temperature as well as those between(also heat production) and each of the following:, rectal temperature, thigh temperature, HR, and age. These results indicated that (1) temperature in the upper extremities was actively maintained at a higher level than temperature in the lower extremities, (2) increased metabolism became a progressively more effective adaptation than redistribution of blood volume, (3) subjects with the lowest BHC tended to increase their metabolism the most, (4)was inversely related to core temperature after the latter fell below normal, (5) HR was unrelated to the increase in, (6) the usual inverse relationship between age and metabolism was not found in the cold, and finally, (7) older subjects generally tended to maintain higher body temperatures than younger subjects.

ISSN:0008-4212    

DOI:10.1139/y70-001

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Previous studies have demonstrated the importance of saliva spreading for evaporative cooling by rats in the heat. In particular, submaxillary–sublingual salivary gland function must be unimpaired for the rat to regulate its body temperature at ambient temperatures above 38 °C. The present study investigated some of the neural components of this thermoregulatory effector system. Bilateral destruction of the chorda tympani, the parasympathetic innervation of the submaxillary–sublingual glands, severely impaired the rat's tolerance of high ambient temperatures. Rats with bilateral electrolytic lesions in the anterior or lateral hypothalamus, placed without chorda tympani damage, also showed pronounced deficits in salivary evaporative water loss and impaired thermal tolerances during heat stress. Other heat loss mechanisms, such as peripheral vasodilatation, may also have been disrupted. These results support previous reports of thermoregulatory deficits in rats following hypothalamic lesions.

ISSN:0008-4212    

DOI:10.1139/y70-002

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Previous investigations demonstrated that the water loss of rats associated with increased salivary evaporation during heat stress is derived from both intracellular and intravascular sources. The present studies indicate that sufficient dehydration of either fluid compartment will impair temperature regulation. Salivary excretion from all dehydrated rats was virtually abolished at ambient temperatures below 38–40 °C, but temperature regulation was still possible if a large temperature gradient existed between the animals and the environment. Above these ambient temperatures, where increased evaporation is essential to survival, the rate of evaporative water loss returned to normal. However, body water reservoirs in dehydrated rats were rapidly depleted, salivary evaporation could not be maintained, and survival times were shortened. In contrast, access to drinking water significantly increased thermal tolerance. These results emphasize the importance of adequate body fluid hydration for evaporative cooling through saliva spreading by rats in the heat. In addition, they indicate that allocation of body water for evaporation takes precedence over conflicting demands for water conservation during heat stress.

ISSN:0008-4212    

DOI:10.1139/y70-003

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Tissue temperature gradients were measured in the front leg, rear leg, back, and rump of the African guinea hog and were fitted to a parabolic model. The depth at which the estimated temperature became equal to the rectal temperature was constant regardless of ambient temperature (in the range −1.1 °C to 37.8 °C).

ISSN:0008-4212    

DOI:10.1139/y70-004

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

This work has demonstrated that when choline is added to the perfusate of isolated livers, these take up the base throughout the duration of the experiment. A sensitive method is described, in which 1,2-14C-choline is used, for estimating the uptake of choline by the liver.

ISSN:0008-4212    

DOI:10.1139/y70-005

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Fluorescein-conjugated antisera to porcine growth hormone localize in acidophils of rat, pig, beef, sheep, and dog pituitaries. Using AT – PAS – orange G stain, two types of acidophils could be distinguished in pig, beef, sheep, and dog pituitaries. Localization of anti-porcine growth hormone was confined to only one acidophil cell type in pituitaries of these species.

ISSN:0008-4212    

DOI:10.1139/y70-006

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Pancreas size and trypsin and chymotrypsin activities were determined for cattle, sheep, rats, mice, and chickens of various ages. Pancreas size per kilogram of live body weight was greater for the nonruminants than for the ruminants. Pancreas trypsin activity per milligram of pancreas dry matter was greater for ruminants than for nonruminants; however, activity per kilogram of body weight was greater for rats and mice than for chickens, which in turn was greater than for ruminants. Chymotrypsin activity was greater for rats and mice than for ruminants on the basis of both pancreas dry matter and body weight. In cattle, chymotrypsin activity per unit of pancreas dry matter was highest in the newborn calf, dropped to one-half that level within 1 week after birth, and then increased only slightly with age up to 1 year. The ratios of chymotrypsin to trypsin activities in the pancreas ranged from 0.39 to 1.20 in the ruminants, except for the newborn calf (1.60), and were greater than 2.0 for the other species. Pancreas size and trypsin and chymotrypsin activity were proportional to body weight1.0with intraspecies comparisons, and proportional to body weight0.73–0.84with interspecies comparisons.

ISSN:0008-4212    

DOI:10.1139/y70-007

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The viscosities of moist and dry air were measured at four temperatures to determine variations due to changes in water vapor content under isothermal test conditions. Paired measurements (240) of volumetric rates of air flow and pressure drops along a tube were made. Corresponding coefficients of viscosity were calculated from the Hagen–Poiseuille equation, laminar flow being assured by limiting maximal Reynolds numbers. The relationship between viscosity (η) and water vapor pressurewas found to be approximately linear. The increase in the work load of the respiratory muscles due to an increase in air humidity, and hence viscosity, from purely physical considerations, appears to be very small compared with the total work of breathing.

ISSN:0008-4212    

DOI:10.1139/y70-008

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

There is a statistically significant positive correlation between the total water content of the arterial wall and the concentration of sodium bound to negatively charged groups of the protein–polysaccharide gel. The fraction of water associated with the protein–polysaccharide gel is located almost exclusively in the inulin space, and is significantly increased in hypertension. The size of this fraction can be reduced by exchanging sodium—the main counterion under physiological conditions—for a divalent ion. There is no difference between calcium and magnesium in this regard. The configuration of the gel, which is given primarily by the relative concentration of the charged groups and the valency of the counterion, determines the size of the inulin space.

ISSN:0008-4212    

DOI:10.1139/y70-009

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A new and rapidly performed in vitro assay of fibrinolytic activity, incorporating turbidimetric measurements of fibrin suspension substrate, is described. The assay allows the write-out of rate reactions by recording the changes in light transmittance through a sample of substrate while it is subjected to enzymatic degradation by fibrinolytic agents. By running the reaction in buffer or serum, the properties of plasminogen activators can be differentiated from those of proteolytic enzymes. Data obtained with this method allow the estimation of relative potencies, quantitative inhibition of enzymes by serum, rate of plasminogen activation, etc., for which examples are given.

ISSN:0008-4212    

DOI:10.1139/y70-010

出版商:NRC Research Press    

年代:1970

数据来源: NRC