A study of the effect of cold on joint temperature and mobility

Exposure to zero and subzero ambient temperatures results in a significant fall in joint temperature, where the knee joint of the cat was used as test object. The fall in rectal, muscle, and “average” skin temperatures for similar exposures is considerably less. Low joint temperature is associated with increased joint stiffness.

Effect of continuous cold exposure on nocturnal body temperatures of man

Effects of continuous cold stress on 24-hour patterns of body temperature were studied in five men. Cold stress consisted in living at 15.6℃ (60℉) for 14 days wearing only shorts. The cold period was preceded and followed by 2 weeks at 26.7℃ (80℉). Activity (minimal) and diet were the same for all periods. One blanket was used at night. Rectal temperature (Tr) and skin temperature (Ts) were measured. Tr during sleep fell more rapidly and to lower values during cold exposure (35.6℃) than during the control period (36.1℃). Ts during sleep was slightly lower in the cold than in the control period; also, Ts did not exhibit the gradual drop characteristic of sleep in the control period. Comparison of Tr and Ts between early and later cold days revealed the following differences: a) nocturnal Tr fell to lower levels on the later cold days; b) nocturnal toe temperatures were 15℃ (27℉) higher on the later cold days. The arch temperatures followed the same pattern as the toes. No significant differences were found in daytime temperatures between early and later cold days. The data suggest that evidence for acclimatization to cold in terms of altered body temperature responses may be fruitfully sought in responses during rewarming and/or sleep.

Submitted on September 19, 1958

Effect of cooling of orbital cortex on exercise hyperpnea in the dog

The significance of cortical contribution to the hyperpnea of exercise has long been debated. An attempt was made to evaluate the role of this factor by cooling the respiratory area of the orbital cortex in 20 experiments on 13 Nembutal-urethane anesthetized dogs before, during and after electrically induced exercise of the hind limbs. Orbital cooling during eupnea produced a 10% decrease in respiratory rate with questionable reduction of minute volume. Cooling induced during exercise resulted in reduction of mean ventilatory volume from 4.37 l/min. to 4.18 l/min. The difference is highly significant statistically and represents 20% of the exercise hyperpnea under these conditions. Cessation of cooling was followed by return to precooling levels. Results indicate that cortical impulses contribute to exercise hyperpnea even under conditions of anesthesia and low levels of exercise and suggest a quantitative approach to evaluation of this factor under more physiologic conditions.

Submitted on July 21, 1958

Effects of cold acclimation on hepatic carbohydrate and lipid metabolism

The acclimation of rats to low environmental temperatures was found to alter the hepatic metabolic response to fasting for 1 day at 0–2°C. Liver glycogen was stabilized, fatty infiltration of the liver did not occur and liver slices were better able to oxidize acetate-I-C14 and palmitate-I-C14 to C14O2. These results provide an excellent example of an acclimation process occurring at the molecular level.

The effect of ions upon the response of smooth muscle to cooling

The slow tonic responses of the anterior byssus retractor of Mytilus edulis to rapid cooling were investigated by simultaneously recording tension and resting potential changes after soaking the muscle in banthine, a powerful neuromuscular blocking agent. The quantitative relations between the amount of cooling and the amount of associated depolarization necessary for contraction at various concentrations of potentiating potassium can be expressed in a family of curves. The plateaus of the curves for sea water and for potassium-free sea water were beneath the depolarization value necessary for contraction, so that it is clear that no amount of cooling with sea water alone or with potassium-free sea water would ever be effective. When the muscle is treated with subthreshold amounts of potassium and rapidly cooled in various concentrations of sodium ion and calcium ion, respectively, the sodium and calcium do not affect the amount of depolarization. Acetylcholine, in subthreshold amounts, has a potentiating effect, but, unlike potassium and cooling, acts through the nervous apparatus. Mytilus muscle will respond to cooling with tonic contraction whenever a critical threshold amount of depolarization is achieved. Cooling alone cannot trigger the contraction since it cannot bring about sufficient depolarization. Cooling can result in contraction, however, if used in conjunction with some other subthreshold depolarizing agent. Cooling affects the contractile mechanism by first causing membrane breakdown and depolarization.

Vasomotor responses to cooling in the extremities of subjects with neurologic lesions

Reflex vascular responses to cooling were studied in subjects with neurologic disorders, with a younger and an elderly "normal" group being used for comparison. By and large the responses were mirror images of those described for the Gibbon-Landis procedure. It was demonstrated that normal reflex responses to cooling as well as to warming are dependent upon the integrity of sympathetic innervation.

Effects of restraint on oxygen consumption of the cold exposed guinea pig

The oxygen consumption of cold exposed, restrained guinea pigs is significantly greater than that of cold exposed, nonrestrained controls. Similar observations have been made for the rat ( Canad. J. Biochem. & Physiol. 33:654, 1955). These data strongly suggest that heat production is greater in the restrained animal than in the nonrestrained control. The hypothermia, then, accompanying restraint in the cold cannot be laid to a decreased muscular activity (muscular activity is actually increased) and a consequently lessened heat production, as suggested by some ( J. Appl. Physiol. 12:214, 1958). It must be due, as demonstrated for the rat ( Am. J. Physiol. 193:557, 1958), to an increased rate of heat loss. The marked physiological changes accompanying restraint should serve as a warning to the investigator who uses restraint for convenience in data collection.

Submitted on July 11, 1958