Preferred temperature of the elderly after cold and heat exposures determined by individual self-selection of air temperature

1. 1. The purpose of the study was to investigate the preferred temperature of the elderly after cold and heat exposures.

2. 2. Eight elderly and 9 young females wearing the same type of clothing were exposed to cold (10°C), moderate (25°C) or hot (35°C) environments for 30 min in the exposure room.

3. 3. Then they moved to the self-control room in which the temperature was set at 25°C, and the room temperature increased or decreased continuously by 0.4°C every minute.

4. 4. The subjects were instructed to operate the switch when they felt uncomfortably warm or cool during a 90-min period.

5. 5. In operating the switch, the changing in room temperature shifted to the opposite direction.

6. 6. The ambient temperature was recorded continuously and analyzed as the preferred temperature, which was defined as the midpoint temperature of the crest and trough of temperature records.

7. 7. The preferred temperatures after the cold exposure were significantly higher than those of other exposure conditions in the elderly.

8. 8. On the other hand, in the young, there was no significant difference in the preferred temperature among the exposure conditions.

9. 9. Although the effect of exposure to cold or hot environments decreased in the latter parts of self-control, the elderly still preferred the higher temperature after cold exposure.

TLV in cold environments

1. 1. The risks encountered during cold exposure are general body cooling or local cooling of parts of th body.

2. 2. Measures of cold stress must account for the effects of climate, clothing and metabolic heat production on heat balance.

3. 3. The combinaed effect of air temperature, mean radiant temperature, humidity and air velocity determines the cooling power of the environment.

4. 4. The cooling power can be easily converted into a required insulation value (IREQ) for whole body heat balance.

5. 5. Extensive cooling of hands and feet may be a limiting factor, even when sufficient total insulation is provided. In addition the cooling effect of wind on unprotected skin must be considered.

6. 6. Recommendation regarding acceptable exposures can be expressed as lowest ambient temperatures and time limits as function of available protection and activity level, with due attention to both general and local effects.

Work at cold storage

1. 1. Work activities in cold storage rooms were assessed by a mailed questionnaire survey of cold storage facilities in Japan.

2. 2. There are nearly 4000 cold storage facilities and about 80% are being kept at temperatures below −20°C.

3. 3. The chief items of stock in storage were marine products, livestock products, frozen food and agricultural products.

4. 4. Methods used for loading and unloading in cold storage rooms are forklift, manual handling, and automatic machines.

5. 5. Use of forklifts appeared to be widespread.

6. 6. Working time differed according to the ambient temperature of the cold storage rooms.

7. 7. Common ailments of cold storage workers are lumbago, bronchitis, neuralgia etc.

Physiological responses and thermal sensations of the elderly in cold and hot environments

1. 1. 10 elderly and 10 college-aged females served as subjects in cold and heat environments. The subjects changed into the standard clothing (0.63 clo), and stayed in the neutral environment (25°C) for 23 min, thereafter they were exposed to the cold (10°C) or hot (35°C) environment for 49 min.

2. 2. Then they returned to the neutral environment, and stayed there for 47 min. Oral temperature, skin temperatures at 10 sites, blood pressure and thermal sensation were measured during the experiments.

3. 3. In the cold environment, the elderly could not reduce heat loss by vasoconstriction as did young people, and their blood pressures increased more rapidly than in young people. In the hot environment, the elderly could not promote heat loss by vasodilation as did young people. Moreover, there is a delayed sensitivity to cold for the elderly. Therefore, in the houses of the elderly, it is important to have heating and cooling systems which also includes the areas where the people do not stay for a long period of time (e.g. toilet, passageways).

Cheek skin temperature and thermal resistance in active and inactive individuals during exposure to cold wind

1. The present study examined the effect of the thermal state of the body (as reflected by rectal temperature) on cheek skin temperature and thermal resistance in active and inactive subjects.

2. Active subjects were exposed to a 30 min conditioning period (CP) (0 °C air with a 2 m/s wind), followed immediately by a 30 min experimental period (EP) (0 °C with a 5 m/s wind). Inactive subjects were exposed to a 30 min CP (22 °C air with no wind), followed immediately by a 45 min EP (0 °C air with a 4.5 m/s wind). The CP period was used to establish a core temperature difference between the active and inactive subjects prior to the start of EP. The 0 °C exposure was replaced with a −10 °C ambient air exposure and the experiment was repeated on a separate day. Subjects were comfortably dressed for each ambient condition.

3. Cheek skin temperature was not significantly higher in active subjects when compared to inactive subjects, but thermal resistance was higher in active subjects.

4. Cheek skin temperature and thermal resistance both decreased as ambient temperature decreased from 0 to −10 °C. The lower cheek thermal resistance at −10 °C may have been due to a greater cheek blood flow as a result of cold-induced vasodilation.

The effect of direct and indirect hand heating on finger blood flow and dexterity during cold exposure

1. The aim of this study was to investigate if finger temperature or finger blood flow is the critical factor for maintenance of finger dexterity during cold exposure.

2. Subjects were exposed twice to −25°C air for 3 h by using a Torso Heating Test (THT) where the torso was maintained to 42°C with a heating vest while the hands were bare, and a Hand Heating Test (HHT) where the hands were heated with heated gloves.

3. Despite similar finger temperatures, finger blood flow was eight times lower and finger dexterity was decreased in HHT as compared to THT.

4. It is concluded that finger blood flow is the critical factor to maintain finger dexterity in the cold.

Muscle potentials and temperature acclimation and acclimatization in flight muscles of workers and drones of Apis mellifera

1. 1.Muscle potentials in fibrillar flight muscles of worker and drone honeybees were recorded extracellularly at thoracic temperatures from 30 to 10°C.

2. 2.Extinction temperatures for muscle potentials were higher in drones for all treatments.

3. 3.Cold acclimation (15°C) lowered extinction temperatures significantly in workers and drones. Acclimitization changed extinction temperatures significantly only in drones.

4. 4.Cold acclimitization had a bigger effect on the rate of muscle potential amplitude decline with decreasing temperature than acclimation.

5. 5.Acclimation and acclimitization had no effect on the increase of muscle potential duration with falling temperature.

6. 6.Muscle potential frequency during shivering was not much different between cold and warm treated bees.

Hatching of freshwater sponge gemmules after low temperature exposure: Ephydatia mülleri (Porifera: Spongillidae)

1. 1.|Gemmules of Ephydatia mülleri can withstand exposure to temperatures down to −80°C for 63 days without loss of hatchability.

2. 2.|Hatching is slowed following exposure to temperatures below −27°C.

3. 3.|There is a slight but significant relationship between gemmule size and the time to hatch.

4. 4.|This species can withstand long-term exposure to winter air temperatures occurring within its known geographic range.

Thermal avoidance and preference in Daphnia magna

1. Water fleas (Daphnia magna) bred at 23°C were non-responsive to temperatures between 13 and 25°C.

2. At the lower (11°C) and upper limits (30°C) their klinokinetic avoidance behaviour showed a larger intraindividual than interindividual variation.

3. Thermal sensitivity for avoidance responses in D. magna was about 1.5°C.

4. For D. magna bred for one parthenogenetic generation at 14°C heat avoidance temperature was about 8°C lower, and cold avoidance temperature was about 1°C higher than in D. magna from 23°C.

5. In group experiments the animals showed some preference for the acclimation temperature.

6. Cold induced stenothermy and warm induced eurythermy in D. magna were related to the mode of reproduction.

The effects of wind and thermal radiation on thermal responses during rest and exercise in a cold environment

1. 1. The purpose of this study was to investigate the effects of thermal radiation and wind on thermal responses at rest and during exercise in a cold environment.

2. 2. The experimental conditions were radiation and wind (R + W), no radiation and wind (W), radiation and no wind (R), no radiation and no wind (C).

3. 3. The air temperature was −5°C. Thermal radiation was 360 W/m². Air velocities were 0.76, 1.73 and 2.8 m/s. Rectal and skin temperatures, heart rate and oxygen consumption were recorded. Thermal and comfort sensations were questioned.

4. 4. There are no significant effects of thermal radiation and wind on the physiological responses except the mean skin temperature. There are significant effects on the mean skin temperature (P < 0.01) and thermal sensation (P < 0.05).

The effect of adaptation to cold and re-adaptation to room temperature on the level of glutathione in rat tissues

1. Glutathione (GSH) was assayed in plasma, liver and IBAT in control (22±1°C) and cold adapted rats (45 days in 5±1°C), and in rats cold adapted and brought back to room temperature after 1, 3, 7 and 15 days.

2. Adaptation to the cold led to reduced GSH in the liver and plasma while the level in intrascapular brown adipose tissue (IBAT) was increased in comparison to controls.

3. On the first day of re-adaptation, plasma GSH was similar to the control level, as were hepatic levels on the first and fifteenth day, but GSH in IBAT remained higher even after fifteen days.

Skin temperatures, thermosensory and pleasantness estimates in case of heterogeneity in the thermal environment

1. 1. Seven thermal conditions were imposed on male sitting subjects (slightly clothed: 0.6 clo).

2. 2. A thermal mannikin was also used to determine the exact operative temperature, T₀.

3. 3. Conditions were: uniform (UN: all parameters at 24.5°C, air velocity at 0.15 ms⁻¹), heated ceiling (HC at 45°C), heated floor (HF at 34°C), cold floor (CF at 14°C), two conditions of one cold wall at 6°C (CW1 and CW2 respectively with and without air temperature compensation) and increased air velocity (AV at 0.4 ms⁻¹).

4. 4. Local skin temperatures and answers to questionnaires were obtained.

5. 5. Skin temperature variations were affected by conditions and slight T₀ changes.

6. 6. Comfort judgments were fairly well related to T₀, especially when expressed as differences between actual non-uniform environment and the uniform one.

7. 7. It is concluded that, in case of non-uniform environments close to thermoneutral zone, thermal comfort or discomfort reflects the climate alterations better than the thermal sensation does.

Exercise in the heat: Effects of dinitrophenol administration

1. 1.|Dinitrophenol (DNP) was administered to rats in two equal dosages (20 mg/kg, 30 min interval); the second injection was followed immediately by exercise (9.14 m/min) in the heat (30°C) or at room temperature (21°C).

2. 2.|At 21°C control (saline-treated) rats manifested a mean endurance of 94 min which was reduced to 32 min among DNP-treated animals.

3. 3.|At 30°C, control rats ran for 65 min (δT_re/min = 0.05°C) while DNP-treated animals had a mean endurance of only 12 min (δT_re/min = 0.22°C).

4. 4.|DNP-treated rats (30°C) manifested no decrements in tail-skin heat loss (δT_sk/min = 0.17°C vs 0.10°C) or saliva secretion (0.78 g/min, DNP vs. 0.19 g/min, control) for their brief treadmill duration.

5. 5.|The increased metabolic heat production of DNP severely reduced performance.

Effect of hygroscopic fabrics on wear comfort in the fluctuating microclimate of clothing

1. 1. A new type of simulator for clothing microclimate was designed and constructed.

2. 2. The simulator was designed to simulate the humidity fluctuation of clothing microclimate as observed under light working conditions and to measure the surface temperature of sample fabrics against the skin by means of a radiation thermometer.

3. 3. Knitted fabrics of cotton and polyester, and polyethylene films were used as specimens with different hygroscopicities.

4. 4. The quick rise and fall in the surface temperature of cotton fabric was observed under rapid fluctuations of the microclimate humidity.

5. 5. Under the same humidity fluctuations, the temperature of polyester fabric rose and fell more moderately than that of cotton fabrics, and the temperature of the polyethylene film did not change. When the rate of change in stimulus temperature is higher, the threshold temperature of warm sensation of the skin comes closer to a given adaption temperature.

6. 6. Therefore, the rapid and large changes in the fabric temperature against the skin, which were observed especially for hygroscopic cotton fabric, must affect the thermal comfort of clothing.

Hyperthermia and exercise performance in guinea-pigs (Cavia porcellus)

1. 1. Ten guinea-pigs with hypothalamic and subcutaneous interscapular thermocouples ran up to exhaustion at 1.5 km/h. Blood lactate concentrations were determined before and after exercise. Four animals exercised at constant ambient temperatures of 15 and 35°C and six other animals ran at variable ambient temperatures, adjusted to stabilize their hypothalamic temperature at 39.5, 40.5 and 41.5°C.

2. 2. Ambient temperature did not influence exercise performance directly. Duration of running was inversely proportional to hypothalamic temperature. There were no correlations between lactate concentration and exercise performance nor between lactate concentration and body temperatures.

3. 3. The results suggest a progressive decrease in exercise performance occurs with increasing body temperature.

Thermoregulatory responses of old men to gradual changes in ambient temperature

1. 1. Thermoregulatory respones to gradual rise and fall in the ambient temperature (T_a) were compared between 8 old (68–78 years) and 8 younger (20–25 years) male subjects.

2. 2. Starting at T_a of 31.5°C (r.h. 40%), T_a was raised to 39.5°C, then lowered to 21.5°C, and raised back to 31.5°C at a constant rate of 0.3°C/min.

3. 3. Noticeable differences in responses between the age groups were as follows: decline of sweating rate and reduction of acral blood flow during room cooling were retarded in the aged group, with wider variations among individuals, compared with those in the younger group; the tympanic and oesophageal temperatures fell considerably during cooling in the elderly group, failing to return to the level at start during the rewarming of the room, in contrast to the younger group.

4. 4. Such sluggish responses may be attributed largely to reduced cutaneous thermal perception with advancing age.

Environmental stress after atropine treatment

1. 1.|Atropine administration resulted in higher skin temperatures in both sensible and insensible environments and a higher core temperature in the hot environment, due to the reduction in whole body sweating. Exercise time was reduced 28 min following atropine in the hot environment, but was not affected in the humid environment.

2. 2.|The effect of heat storage (significantly higher after atropine) was shown to be greater in the hot environment due to inadequate sweat secretion for subsequent evaporative cooling. In the warm environment, enhanced sensible heat loss resulted in more effective thermoregulation.

3. 3.|Based on the effective temperature (ET^*) it is suggested that exercise in the heat can be accomplished during environmental stress at warm temperatures after atropine treatment.

The effect of acclimation temperature and the removal of peripheral temperature receptors on body temperature preference in the cockroach, Periplaneta americana

1. 1.|Body temperature preferences were compared between cockroaches acclimated to different ambient temperatures and between 25°C acclimated cockroaches and cockroaches deprived of their peripheral temperature receptors.

2. 2.|Acclimation to 35°C resulted in a significantly higher mean body temperature and low body temperature selected compared with 25°C acclimated cockroaches.

3. 3.|Cockroaches deprived of their peripheral temperature receptors showed a significantly higher mean high body temperature selected when compared to normal 25°C acclimated cockroaches.

4. 4.|It is concluded that cockroach temperature regulation is more precise than expected and that central temperature receptors are the primary sensing elements for cockroach thermoregulation.

Thermoregulatory effects of central injection of noradrenaline in the new-born columbian ground squirrel (Spermophilus columbianus)

1. 1.Effects of centrally injected noradrenaline (NA) into new-born (12–300 h. post-partum) Columbian ground squirrels (Spermophilus columbianus) were studied to provide comparative data on ontogeny of the thermoregulatory pathways in a hibernating species.

2. 2.At warm ambient temperatures (32–34°C, similar to nest temperature), NA increased heat production (47–92%). rectal temperature (0.27–1.73°C), and axillary temperature (0.59–1.92°C). Peak magnitudes of heat production increased with increasing age on a per unit weight basis.

3. 3.At lower temperatures (28–31°C), NA had no effect on heat production.

4. 4.The data indicate that metabolic and thermal responses to NA in neonates of hibernating species are comparable (e.g. rabbit. guinea pig) or different (e.g. lamb) from those observed in neonates of non-hibernating species.

Effect of heat and cold exposure on the rat brain monoamine oxidase and antioxidative enzyme activities

1. Changes in MAO and antioxidative enzymes copper-zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD) and catalase (CAT) activities were examined in the hypothalamus and the hippocampus of Wistar rats exposed to cold stress (6 °C) for 180 min and heat stress (38 °C) for 60 min.

2. Extreme environmental temperatures caused stressor-specific changes in the hypothalamic and hippocampal MAO and antioxidative enzyme activities, being dependent on the stressor applied (cold or heat) but not on the brain region studied (the hypothalamus or hippocampus).