摘要:

Forty-five dogs were exposed to nine different environmental conditions (five dogs per condition) consisting of three ambient temperatures (100 °F, 110 °F, and 120 °F) and relative humidities (30%, 60%, and 90%). After an initial control period of 30 minutes (ambient 21–24 °C) the animals were exposed to one of the experimental conditions forhours or until rectal temperature reached 42.0 °C. Under combined conditions of high temperature and humidity the non-biothermally involved consequences of panting became evidenced by an increase in blood pH, a decrease in blood CO2(as a result of the thermally forced hyperventilation), and an increase in blood O2. The more severe the heat load (combined temperature and humidity) the greater was the rate of elevation of rectal temperature over control levels. It was evident that both relative humidity and ambient temperature were drives for increasing respiratory rate. It was also evident that increased humidity as well as increased temperature facilitated the rate of change of rectal temperature, blood pH, and blood CO2and O2concentrations. It appears possible that only under heat loads in which rectal temperature can be maintained at control levels by panting can the shift in acid–base balance be avoided.

ISSN:0008-4212    

DOI:10.1139/y67-001

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Eight male human subjects, resting supine, and wearing swim trunks only, were exposed to an ambient temperature of 8.5 °C for 1 hour in the first week of each month from February 1964 to January 1965 inclusive. Skin, rectal, and air temperatures were measured with thermistor probes. Percentage oxygen in expired air and minute ventilation were measured, and heat production was calculated by Weir's method. Electrical activity from the muscles of all four limbs was measured to determine shivering response. Control values of resting respiration and heat production were obtained under comfortably warm conditions and showed marked seasonal variation, with minimum values in spring and maximum values in later summer. In the response to acute cold exposure, marked seasonal changes were found also which were superimposed on the seasonal changes in control values. The response to cold exposure indicated maximum acclimatization to cold in the spring and minimum in later summer. These results are discussed in terms of three modes of response to the cold stress: (i) insulative cooling, (ii) shivering thermogenesis, and (iii) nonshivering thermogenesis. The degree of acclimatization and temperature of exposure may determine the individual mode of response.

ISSN:0008-4212    

DOI:10.1139/y67-002

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Studies were carried out in anesthetized dogs to elucidate the mechanism of action of octanoate on glucose metabolism.Octanoate infusion in intact healthy dogs significantly decreased plasma glucose concentration, and in four out of seven dogs it raised plasma insulin concentration in peripheral blood. In contrast, intravenous administration of octanoate in four totally pancreatectomized dogs produced only small changes in plasma glucose concentration. These data suggest that the hypoglycemic action of octanoate may be mediated by increased secretion of insulin.The meankvalue (of plasma glucose concentration) of intravenous glucose tolerance tests was significantly higher (2.38/minute) in healthy dogs that received an infusion of octanoate than in dogs that did not (1.2/minute). Octanoate also produced in healthy dogs greater increases in plasma insulin concentrations of peripheral blood during the tolerance tests. Furthermore, when delivered during a continuous intravenous administration of glucose (about 8 mg/kg per minute), octanoate infusion had no effect on either plasma glucose concentration or the rate of disappearance of glucose-U-14C from plasma to tissues. These findings indicate that octanoate does not impair glucose utilization in healthy dogs but actually improves tolerance of an intravenous glucose load, probably by stimulating greater release of insulin. These findings in vivo are discussed in the light of opposite effects of octanoate in vitro, to be described elsewhere, on glucose metabolism in the isolated heart and fat pad of rats.

ISSN:0008-4212    

DOI:10.1139/y67-003

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The rate of removal of24Na from a deposit in the rabbit's foot was used to determine the degree of involvement of arteriovenous anastomoses in the blood flow of cold-induced vasodilation, in the rewarming following intense vasoconstriction, and in reactive hyperemia. The results indicate that in the first two cases the total flow is through the arteriovenous anastomoses. In reactive hyperemia an initial flow which is partly capillary and partly through the anastomoses gives way to a flow which is entirely through the anastomoses.

ISSN:0008-4212    

DOI:10.1139/y67-004

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Mice with established, immunologically compatible tumors were allowed to breathe air, O2, or 5% CO2and 95% O2at 1 and 3 atmospheres pressure. Tumor blood flow was determined by using the thermal circulation index, and oxygenation was measured polarographically. Pure oxygen at 1 atmosphere had no significant effect on blood flow within the tumor and in normal skin, but inhalation at 3 atmospheres decreased flow within both tissues. The addition of 5% CO2to the oxygen increased flow at both pressures. Oxygenation was often improved in anoxic areas within the tumor on breathing 100% O2at 1 atmosphere and in almost all animals at 3 atmospheres; the addition of 5% CO2at either pressure usually further improved the oxygenation, but sometimes had the opposite effect at 3 atmospheres. The application of these results to the use of hyperbaric O2in radiotherapy is discussed.

ISSN:0008-4212    

DOI:10.1139/y67-005

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Lesions were placed in the left ventromedial tegmental area of the brains of nine monkeys (Macaca mulatto). After 1–4 months, the brains were removed, and the striatum was dissected and prepared for chemical analysis. In seven animals in which the lesion was strictly unilateral, the striatal dopamine was very much reduced below the level found on the intact side of the brain. In the two monkeys in which the lesion impinged on the right side of the brain, the concentration of dopamine was reduced on both sides. Homovanillic acid and 3,4-dihydroxyphenylacetic acid, metabolic derivatives of dopamine, were measured in the left and right striata of four and five monkeys respectively. Both compounds were present at subnormal concentrations on the side of the lesion. The concentration of homovanillic acid did not fall to as great an extent as did that of dopamine. These results are discussed in relation to data reported by others in regard to (a) animals treated with tranquilizing drugs, and (b) brains of patients who died with Parkinson's disease.

ISSN:0008-4212    

DOI:10.1139/y67-006

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Lewis and Pickering reported in 1933 that warming occurred later in cool than in warm fingers in response to body heating. Factors which may be responsible were investigated. Measurement of rate of blood flow in the feet by venous occlusion plethysmography during body heating showed that vasodilatation in the feet occurred at the same time in a cool foot (18 to 23 °C) as in a warm (30 to 35 °C) but that warming of the cooler foot might be delayed for some time until the increase in flow was 0.5 ml/100 ml of foot per minute or more. In control experiments, with both feet in cool water or both in warm, the increase in blood flow during body heating started at the same time in both feet. Warming also began at the same time in both feet, but in the cool control experiments, warming often began later than did increase in flow. It is suggested that precooling of arterial blood may account for the delay in warming when the extremity is initially cool and the increase in blood flow is at first small during indirect vasodilatation.

ISSN:0008-4212    

DOI:10.1139/y67-007

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Local cold markedly reduces the rate of blood flow in the extremities. Experiments were performed to see whether it also increased the sensitivity of vascular smooth muscle to noradrenaline in terms of a reduced threshold dose. Rate of blood flow in the feet was measured by venous occlusion plethysmography. The plethysmographs were filled with water at 21 °C for the left foot and 34 °C for the right. Noradrenaline in doses of 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 μg/minute were infused intravenously for periods of 5 to 7 minutes. Rate of flow during noradrenaline infusion was expressed as a percentage of the rate just before noradrenaline. Fifteen experiments on 13 subjects were performed but not all doses were administered in each experiment. The mean of the percentage flow rates for all infusions at a given dose of noradrenaline was not less than 100% for either foot until 0.8 μg/minute was administered, when flow was reduced in both warm and cool feet. Thus, cooled vessels were not shown to be more sensitive than warm vessels. Noradrenaline infused at 3.2 μg/minute caused a significantly greater reduction in flow rate in the cool than in the warm feet but this is not interpreted as a greater reactivity of the cooler vessels to the drug.

ISSN:0008-4212    

DOI:10.1139/y67-008

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The relative importance of the inhibition of vasoconstrictor nerves and of concomitant local warming in the production of indirect vasodilatation was investigated in terms of the decrease in critical opening pressure (COP) of digital vessels during body heating. The COP of vessels in a finger of each hand was measured when both hands were kept at about 21 °C during body heating in control experiments and when one of the hands was allowed to warm in air in test experiments. In eight control experiments the COP's of vessels in both fingers fell together. In 25 test experiments they fell together in both fingers until the hand in air began to warm. The COP then fell more rapidly and farther in the finger which warmed. In the test experiments the difference between the reductions in COP in the two fingers was attributed to the effect of local warming. The total reduction in the hand which was prevented from warming was ascribed to inhibition of neurogenic smooth muscle tone. On the average, local warming reduced the COP by 1.3 mm Hg for each increase of 1 °C. Warming occurred when the COP was reduced to about 25 to 35 mm Hg. However, much higher values of COP can exist in the constricted subject. Therefore the initial smooth muscle constricting force may have to be greatly reduced by inhibition of vasoconstrictor nerves before appreciable warming occurs. Then local warming may play an important role in determining the degree of vasodilatation that occurs.

ISSN:0008-4212    

DOI:10.1139/y67-009

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The effect of local temperature on the in vivo reactivity of vascular smooth muscle was studied. Reactivity was measured as the increase in critical opening pressure (COP) of digital vessels caused by intravenous infusion of 5 μg of noradrenaline per minute. With one hand cool (22 °C) and the other warm (34 °C) in test experiments or both hands either cool or warm in control experiments, simultaneous measurements were made of the increase in COP of vessels in both middle fingers in response to the noradrenaline. In control experiments the mean increase in COP was similar in right and left fingers, but in test experiments the mean increase was greater in the warm finger than in the cool one. Warm vessels were more reactive to noradrenaline than cool ones (p < 0.01). Because a short period of ischemia is involved in the measurement of COP, other experiments were performed in which the effect of duration of ischemia on the COP, with and without a continuous intravenous infusion of noradrenaline, was ascertained. They suggested that the estimated COP would, in most cases, be about 3 mm Hg less than the COP existing just before the measurement. These results also indicated that although the rate of fall of COP during ischemia was slightly greater for a higher initial COP, the ischemia involved did not invalidate the comparison of the increases in COP caused by noradrenaline in warm and cool fingers, as an index of relative arteriolar reactivity in the test reactivity experiments.

ISSN:0008-4212    

DOI:10.1139/y67-010

出版商:NRC Research Press    

年代:1967

数据来源: NRC