Rewarming In Water Research Articles

Brief Rewarming Blunts Hypothermia-Induced Alterations in Sensation, Motor Drive and Cognition

Background: It is well known that cold exposure experienced during occupational or recreational activities may adversely affect motor, cognitive performance, and health. Most research has used prolonged passive external rewarming modalities and focused on the direct effects on the kinetics of physiological and psychological responses in hypothermic subjects. However, the brief whole body rewarming effects on physiological and psychological responses in parallel with functional consequences on cognitive and neurophysiological functions have not been investigated. This study explores these effects in 12 healthy young men.Methods: Subjects (20 ± 1 years) participated in 4 randomized trials, which were designed to compare the effects of whole-body brief (5-min) rewarming in 37°C water with rewarming for the same duration in 24°C (air) thermoneutral environment in mildly hypothermic subjects. After each rewarming, indicators of neuromuscular function (reflexes, central activation ratio, electromyography of exercising muscle, and contractile properties of calf muscles) and cognitive function (attention, simple motor speed, and information processing speed) were assessed.Results: Compared to rewarming in thermoneutral environment, after brief rewarming in 37°C water, significantly lower metabolic heat production (MHP) (206 ± 33.4 vs. 121.9 ± 24.3 W·m2, P < 0.01), heart rate (76 ± 16 vs. 60 ± 12 b·min−1, P < 0.01), cold strain (6.4 ± 3.1 vs. 5.3 ± 2.7, P < 0.01), improved thermal comfort and induced cessation of shivering were found. Electrically induced maximum torque amplitudes increased (P100, 102.8 ± 21.3 vs. 109.2 ± 17.5 Nm and PTT100, 83.1 ± 17.1 vs. 92.7 ± 16.0 Nm, P < 0.05), contraction half-relaxation time decreased (599.0 ± 53.8 vs. 589.0 ± 56.3 ms, P < 0.05), and Mmax-wave latency shortened (17.5 ± 2.2 vs. 15.6 ± 2.0 ms, P < 0.05) after 37°C water rewarming. Unlike rewarming in thermoneutral environment, 37°C water rewarming blunted the hypothermia-induced alterations in neural drive transmission (4.3 ± 0.5 vs. 3.4 ± 0.8 mV H-reflex and 4.9 ± 0.2 vs. 4.4 ± 0.4 mV V-wave, P < 0.05), which increased central fatigue during a 2-min maximum load (P < 0.05). Furthermore, only in brief warm water rewarming cerebral alterations were restored to the control level and it was indicated by shortened reaction times (P < 0.05).Conclusions: Brief rewarming in warm water rather than the same duration rewarming in thermoneutral environment blunted the hypothermia-induced alterations for sensation, motor drive, and cognition, despite the fact that rectal and deep muscle temperature remained lowered.

Hand and Finger Dexterity as a Function of Skin Temperature, EMG, and Ambient Condition

This article examines the changes in skin temperature (finger, hand, forearm), manual performance (hand dexterity and strength), and forearm surface electromyograph (EMG) through 40-min, 11 degrees C water cooling followed by 15-min, 34 degrees C water rewarming; additionally, it explores the relationship between dexterity and the factors of skin temperature, EMG, and ambient condition. Hand exposure in cold conditions is unavoidable and significantly affects manual performance. Two tasks requiring gross and fine dexterity were designed, namely, nut loosening and pin insertion, respectively. The nested-factorial design includes factors of gender, participant (nested within gender), immersion duration, muscle type (for EMG), and location (for skin temperature). The responses are changes in dexterity, skin temperature, normalized amplitude of EMG, and grip strength. Finally, factor analysis and stepwise regression are used to explore factors affecting hand and finger dexterity. Dexterity, EMG, and skin temperature fell with prolonged cooling, but the EMG of the flexor digitorum superficialis remained almost unchanged during the nut loosening task. All responses but the forearm skin temperature recovered to the baseline level at the end of rewarming. The three factors extracted by factor analysis are termed skin temperature, ambient condition, and EMG. They explain approximately two thirds of the variation of the linear models for both dexterities, and the factor of skin temperature is the most influential. Sustained cooling and warming significantly decreases and increases finger, hand, and forearm skin temperature. Dexterity, strength, and EMG are positively correlated to skin temperature. Therefore, keeping the finger, hand, and forearm warm is important to maintaining hand performance. The findings could be helpful to building safety guidelines for working in cold environments.

Cryopreservation of In Vitro. Grown Apical Shoot Tips of Strawberry by Vitrification.

After the strawberry shoots on culture medium were cold-hardened at 5°C for 20-30 days, shoot tips were dissected and precultured at 5°C for 1 day on MS medium containing 2 M glycerol and 0.3M sucrose. Precultured 10 shoot tips were placed in 2.0ml cryotubes each, and treated with a mixture of 2M glycerol and 0.3M sucrose for 20min at 25°C. They were then treated with PVS2 solution for 50min at 25°C, and immersed into LN. After rapid rewarming in water at 35°C, they were transferred onto the MS medium containing 1gl-1 PVP and 0.2mgl-1 BA and grown under standard conditions. By this protocol, survival rate of cryopreserved “Donner” shoot tips reached 93%. This protocol was successfully applied to 7 other races or lines of strawberry with high survival rates. These results prompt us to setting up large-scale strawberry LN storage system.

New Rat Model for the Research of Stress Ulcer Accompanying Subarachnoid Hemorrhage

Background: Various rat models have been used to study subarachnoid hemorrhage related to a stress ulcer. However, these models have many problems such as high mortality, low success rates, and a bias due to a long procedure time. The purpose of this study was to develope a more reliable rat model for the study of subarachnoid hemorrhage related to a stress ulcer. Methods: Sprague-Dawley rats were anesthetized, and various volume of autologous blood were injected into the basal cistern by percutaneous injection. Mild stress consisting of restraint plus 4oC cold water immersion, 20oC cold water immersion, or 4o C cold water immersion with 40oC water rewarming were used to produce a stress ulcer. Thirty minutes after water immersion, rats were euthenized and the relative ulcer length (RUL) was measured. Results: Experimental subarachnoid hemorrhage by an injection of 0.2 ml autologous blood and three cycles of restraint plus 4oC cold water immersion with 40oC water rewarming produced a marked ulceration without mortality and a significant neurologic deficit. Conclusions: An injection of 0.2 ml autologous blood combined with three cycle of restraint plus 4oC cold water immersion with 40oC water rewarming is an ideal model to study subarachnoid hemorrhage related to a stress ulcer.

Survival of Plant Tissue at Super-Low Temperatures. IV. Cell Survival with Rapid Cooling and Rewarming

Thin unmounted cortical tissue sections from winter twigs of the mulberry tree were held with a thin forceps and rapidly immersed in liquid nitrogen from room temperatures without prefreezing. They were rewarmed; rapidly in water at 10 degrees to 40 degrees , or slowly, in air at room temperatures. In those sections rapidly rewarmed, all survived. None survived in those sections rewarmed slowly in air.Tissue sections mounted between coverglasses with water were extracellulary prefrozen at the temperatures low enough to dehydrate almost all of the freezable water in cells. These sufficiently prefrozen cells could survive immersion in liquid nitrogen, and the survival value was very little affected by the rates of cooling to and rewarming from super-low temperatures. With insufficient prefreezing at higher temperatures, however, the rewarming process seriously influenced the survival value of cells frozen at super-low temperatures. Slow rewarming in air destroyed all of the cells, while rapid rewarming in water at 30 degrees did not affect them. An abrupt decrease in the survival value in insufficiently prefrozen cells during rewarming was also observed at temperatures above approximately -50 degrees following immersion in liquid nitrogen. Very little decrease in the survival value was observed in any of the cells that had been sufficiently prefrozen.These results indicate that cells which are insufficiently prefrozen may contain freezable water which nucleates during rapid cooling in liquid nitrogen and then grows during the subsequent slow rewarming into ice masses which destroy the viability of the cells. Such fatal intracellular freezing rarely occurs in sufficiently prefrozen cells, irrespective of the rate of cooling to or rewarming from super-low temperatures.

Effect of rapid rewarming on tissue survival of frozen rabbits' feet.

The nature of the beneficial effect worked by rapid rewarming of frozen tissue on final tissue survival was investigated in rabbits' hind feet. An attempt was made to separate the effect of shortening the exposure time, which is inherent in rapid rewarming, from the effect of rapid rewarming per se. A method for producing a standard degree of cold injury was worked out based on ‘time frozen,’ the assumption being made that ice crystals are mainly responsible for damage in frozen tissue. The basic procedure was varied by changing times and/or temperatures. Results indicate that increasing the ‘time frozen’ is less harmful than increasing the thawing period, that rewarming in water at 43°C increases tissue survival while rewarming at 37°C does not. At least three independent factors apparently contribute to the final injury of frozen tissue: a) length of time frozen; b) temperature during the frozen state; and c) temperature during thawing. Submitted on August 13, 1957