Muscle glycogen depletion during exercise at 9 degrees C and 21 degrees C

This study compared glycogen depletion in active skeletal muscle after light and moderate exercise in both cold and comfortable ambient conditions. Twelve male subjects (Ss) were divided into two groups equally matched for the submaximal exercise intensity corresponding to a blood lactate concentration of 4 mM (W4) during cycle exercise. On two separate days Ss rested for 30 min at ambient temperatures of either 9 degrees C or 21 degrees C, with the order of temperature exposure being counter-balanced among Ss. Following rest a tissue specimen was obtained from the m. vastus lateralis with the needle biopsy technique. Six Ss then exercised on a cycle ergometer for 30 min at 30% W4 (range = 50 - 65 W) while the remaining group exercised at 60% W4 (range = 85 - 120 W). Another biopsy was taken immediately after exercise and both samples were assayed for glycogen content. Identical procedures were repeated for the second environmental exposure. No significant glycogen depletion was observed in the Ss exercising at 30% W4 in 21 degrees C, but a 23% decrease (p = 0.04) was observed when the same exercise was performed at 9 degrees C. A 22% decrease (p = 0.002) in glycogen occurred in the 60% W4 group at 21 degrees C, which was not significantly different from that observed during the same exercise at 9 degrees C. The results suggest that muscle substrate utilization is increased during light exercise in a cold environment as compared to similar exercise at a comfortable temperature, probably due to shivering thermogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Geographic mosaics of phenology,host preference,adult size and microhabitat choice predict butterfly resilience to climate warming

The climate‐sensitive butterfly Euphydryas editha exhibited interpopulation variation in both phenology and egg placement, exposing individuals to diverse thermal environments. We measured ‘eggspace’ temperatures adjacent to natural egg clutches in populations distributed across a range of latitudes (36°8′–44°6′) and altitudes (213–3171 m). Eggs laid > 50 cm above the ground averaged 3.1°C cooler than ambient air at 1 m height, while eggs at < 1 cm height averaged 15.5°C hotter than ambient, ranging up to 47°C. Because of differences in egg height, eggs at 3171 m elevation and 20.6°C ambient air experienced mean eggspace temperatures 7°C hotter than those at 213 m elevation and ambient 33.3°C. Experimental eggs survived for one hour at 45°C but were killed by 48°C. Eggs laid low, by positively geotactic butterflies, risked thermal stress. However, at populations where eggs were laid lowest, higher oviposition would have incurred incidental predation from grazers. Interpopulation variation in phenology influenced thermal environment and buffered exposure to thermal stress. At sites with hotter July temperatures, the single annual flight/oviposition period was advanced such that eggs were laid on earlier dates, with cooler ambient temperatures. The insects possessed two mechanisms for advancing egg phenology; they could advance timing of larval diapause‐breaking and/or shorten the life cycle by becoming smaller adults. Mean weight of newly‐eclosed females varied among populations from 92 to 285 mg, suggesting that variable adult size did influence phenology. Possible options for in situ mitigation of thermal stress include further advancing phenology and raising egg height. We argue that these options exist, as evidenced by current variation in these traits and by failure of E. editha to conform to restrictive biogeographic constraints, such as the expectation that populations at equatorial and poleward range limits be confined to higher and lower elevations, respectively. This optimistic example shows how complex local adaptation can generate resilience to climate warming.     

Time-of-Day Effects on Anaerobic Muscular Power in a Moderately Warm Environment

This study evaluated the influence of a neutral vs. a moderately warm environment on the diurnal variation in muscular power. Twelve male subjects [27.0 (±4) years] performed two different jump tests [a squat jump (SJ) and a counter-movement jump (CMJ)] and a brief maximal sprint on cycle ergometer (CS) in four different conditions (morning/neutral, morning/moderately warm and humid, afternoon/neutral, and afternoon/moderately warm and humid). The morning experiments were conducted between 07:00 and 09:00 h, and the afternoon experiments were conducted between 17:00 and 19:00 h. The mean laboratory temperatures and humidity were 20 (±1)°C, 70 (±5)% and 29 (±1)°C, 57 (±4)% for the neutral and moderately warm and humid conditions, respectively. Rectal temperature and leg skin temperature were significantly dependent on both time-of-day and ambient temperature. An interaction effect (P < 0.05) was noted between time-of-day and ambient temperature for the power developed for the CMJ, the SJ, and half of a pedal revolution during the cycling sprint. In summary, (i) the same subjects were influenced by time-of-day differently, depending on the ambient temperature during testing; (ii) time-of-day affected muscular performance only in the neutral condition, (iii) the moderately warm and humid condition blunted the diurnal variation in muscular performance, and (iv) the effect of the ambient temperature was dependent on time-of-day.     

Thermal biology of the Central Asian blunt-nosed viper (Macrovipera lebetina turanica) from Nuratau Crest and the Chernov blunt-nosed viper (Macrovipera lebetina černovi) from Western Kysylkum

The ecology of the Central Asian blunt-nosed viper (Macrovipera lebetina turanica) inhabiting the Nuratau Crest of Uzbekistan is described. The temperature conditions of the environment and the spatialtemporal structure of the viper activity are represented, which made it possible to find some of thermobiological characteristics. The temperature diapason of full activity of this viper constitutes approximately 17–34°C. The temperature of thermostabilization is in the range of 26–31°C, nocturnal temperatures are elevated from 9–15°C to 18–23°C in spring and summer, respectively, and diurnal body temperatures are decreased from 18–22°C to 10–15°C. Feeding and digestion are normal in blunt-nosed vipers at 25°C, which is below the diurnal temperature variation. In spring, the light phase duration is rapidly increased from 3–6 h to 14 h or more. This length of time and the large diurnal variation in the body temperature from 18°C to 20–22°C facilitate active and efficient coupling. Later, the diurnal body temperature is decreased to 13–18°C, which facilitates successful recovery in males and pregnancy in females. Plots for the average viper body temperature in different seasons are represented. The thermobiological characteristics of the bluntnosed viper of Macrovipera lebetina ěrnovi are similar to M. l. turanica.     

Influence of programmed circadian temperature changes upon levels of luteinizing hormone in the bovine

A study was undertaken to determine the effects of controlled circadian patterns of elevated ambient temperatures (21-34 degrees C) upon the venous levels of luteinizing hormone (LH) in the bovine. Venous blood was collected from 8 16-month-old Angus heifers by indwelling cannulae to study LH levels in animals subjected to 2 ambient temperature regimes within 7 times 7.5 times 2.7 m psychrometric chambers. The control temperature regime was 17-21 degrees C diurnal variation, and the experimental temperature regime was 21-34 degrees C diurnal variation. The experimental regime significantly ( less than .05) decreased preovulatory and basal LH levels based upon 0800 and 1600 hour samples. Mean preovulatory LH levels were 6.4 ng/ml, where standard error of the mean (SEM) = 1.9 and number (n) = 16, in the control environment and 2.7 ng/ml (SEM = .9, N = 16) in the experimental regime. Comparable values for basal levels were .8 ng/ml (SEM = .02, n = 176). 7 of 8 animals exhibited an LH surge (greater than or equal to 4 ng/ml) while exposed to the control environment compared to only 3 of 8 at the experimental environment.     

Temperature dependence of the microwave properties of aqueous solutions of ethylene glycol between +15 degrees C and -70 degrees C.

The values of the dielectric constant and of the loss tangent for samples of 0 m (distilled H₂O), 1 m, 2 m, 3 m, 4 m, 5 m, 10 m, and 100% ethylene glycol were determined over the temperature range of +15 °C to ?70 °C. An operating frequency of 1.40 GHz to 1.55 GHz was used, allowing the results to be applied directly to both 0.915 GHz and 2.450 GHz studies. Strong temperature and concentration dependencies were found; low concentration solutions tended to behave similarly to water, while higher concentration solutions were more independent. Peak values and discontinuities occurred at different temperatures, depending on concentration. Five molar ethylene glycol was indicated as a near optimum concentration based on toxicity, cryoprotection, and microwave power absorption considerations. A study of blends of cryoprotectants is suggested.     

Growth at 37 degrees C of the EGs strain of the amoeboflagellate Naegleria gruberi containing viruslike particles. I. Nuclear changes

Naegleria gruberi amoebae, EG_s strain, containing viruslike particles (VLP) were grown at temperatures of 21° and 37°C. At 21°C, the amoebae displayed the morphological structures associated with development of the VLP's. At 37°C, however, gross morphological modifications and new structures appeared. When amoebae were at 37°C for less than 12 hr, nuclei were found to have a larger number of VLP's than amoebae at 21°C. Exposure of the amoebae to the higher temperature for 12–24 hr resulted in a scarcity of particles. Large bundles of microtubulelike fibrils were present in the nucleoplasm of amoebae at 37°C, and, in addition, the nuclei showed degenerative modifications. The fibrillar changes were not due to the elevated temperature alone since a substrain of EG_s (=EG_B) not infected with VLP's exhibited no nuclear modifications. It is assumed that the elevated temperature accelerated and enhanced a lytic effect of the VLP's upon the cells.     

Effect of varying environmental temperature on heat output and finger skin temperature

Heat output from the right hand was estimated on six healthy young men at varying ambient temperatures, in a temperature-controlled room maintained at 5°, 10°, 15°, 20°, 25°, 30° and 35°C at weekly intervals. The skintemperature of the index finger of both the hands, wrist vein of the right hand and oral temperature, were also recorded during the study. Results indicate that the heat output varies significantly with the changes in ambient temperatures, at higher ranges only. This variation is negligible at lower ambient temperatures. Other parameters supported this observation.     

The influence of ambient temperature on the abundance of Poaceae pollen

The sampling of pollen concentrations over six seasons in north London has revealed the importance of temperature in influencing the start, severity, daily and diurnal variation of Poaceae pollen seasons. Using accumulated degree days above 6°C and rainfall amount as predictors, models have been developed which account for 96% of the variation in the starting date and 91% of the variation in the severity of the Poaceae pollen season. Maximum daily temperature is an important influence on the daily pollen count although this relationship is not linear and maximum daily temperatures within the range 21.1–25°C are associated with the highest daily pollen concentrations. Likewise, when the two-hourly variation of pollen concentration is examined, temperatures within 2–4.9°C above the normal diurnal range, rather than in excess of 5.0°C, are found to be associated with the highest two-hourly concentrations. Occasional night-time maxima of pollen concentration have also been recorded and these are examined in relation to the possibility of temperature inversions, although few conclusive results have emerged.     

Effects of microwave exposure and temperature on survival of mice infected with Streptococcus pneumoniae

Female CD-1 mice were injected with an LD₅₀ dose of Streptococcus pneumoniae and then exposed to 2.45 GHz (CW) microwave radiation at an incident power density of 10 mW/cm² (SAR = 6.8 W/kg), 4 h/d for 5 d at ambient temperatures of 19 °C, 22 °C, 25 °C, 28 °C, 31 °C, 34 °C, 37 °C and 40 °C. Four groups of 25 animals were exposed at each temperature with an equal number of animals concurrently sham-exposed. Survival was observed for a 10-d period after infection. Survival of the sham-exposed animals increased as ambient temperature increased from 19 °C–34 °C. At ambient temperatures at or above 37 °C the heat induced in the body exceeded the thermoregulatory capacity of the animals and deaths from hyperthermia occurred. Survival of the microwave-exposed animals was significantly greater than the shams (～20%) at each ambient temperature below 34 °C. Based on an analysis of the data it appears that the hyperthermia induced by microwave exposure may be more effective in increasing survival in infected mice than hyperthermia produced by conventional methods (ie, high ambient temperature). Microwave radiation may be beneficial to infected animals at low and moderate ambient temperatures, but it is detrimental when combined with high ambient temperatures.     

Effects of low-temperature acclimation on the survival and cold tolerance of an antarctic mite

The effects of long-term exposures to constant temperatures (+4, 0, −5, −10, −15 and −20°C) on the survival of a cryptostigmatid mite, Alaskozetes antarcticus, were studied during 1983–1984 on Signy Island, South Orkney Islands, in the maritime Antarctic. Field-fresh samples collected during the austral summer showed very large (e.g. about 60 percentage points) variations in survival when placed at constant temperatures, as a result of collection-date effects. Pretreatment acclimations (10-day) at +4 and 0°C (especially) reduced this variation. Short-term modulations in cold-hardiness levels were related to ambient temperature fluctuations. However, samples collected on the same occasion, from microhabitats 20 m apart, also showed significant cold-hardiness variation. For twelve summer samples, survival after 24 h at −15°C was highly correlated with supercooling capacity. Winter samples showed little variation in survival, interms of collection-date. Percentage survival remained greater than 85% at −5, −10 and −15°C, for exposures up to 100 days. Samples with median supercooling points of about −30°C, showed 52% survival after 250 days at −15°C, and 73% survival after 100 days at −20°C. At −15°C, supercooling capacity was used up at an estimated rate of 0.06 deg day⁻¹, as a result of a time-temperature interaction effect on the probability of heterogeneous nucleation. Adult mites showed 78% survival after 21 days encasement in distilled water ice, at −15°C. Survival differences between post-larval stages were not detected. In conclusion, survival ability under controlled laboratory conditions appeared to exceed the requirements of average winter-habitat temperatures, but the effects of fluctuating and extreme temperatures require investigation. Supercooling points are considered to be accurate indicators of low-temperature survival capability in this species.     

Photosynthesis in cold acclimated leaves of plants with various degrees of freezing tolerance

The objective of this study was to compare the photosynthetic changes during cold acclimation in various plant types able to acquire different degrees of freezing tolerance. Four herbaceous and six woody plants were hardened under natural or artificial conditions and – after determination of their frost resistance (LT₅₀) – the net photosynthetic rate at an ambient CO₂ of 33 Pa (P_n33), the dependencies of P_n to light and to CO₂ and the room temperature chlorophyll a fluorescence were recorded under optimal conditions. Herbaceous plants acquired freezing tolerances to temperatures between ?10 and ?15°C when hardened at temperatures around 0°C. Most leaves fully developed prior to frost hardening exhibited typical symptoms of senescence after frost hardening. In non-senescing leaves P_n33 was reduced by 15 to 50% mainly due to a reduced stomatal conductance. After hardening at temperatures around ?10°C Brassica survived down to ?24°C, but P_n33 was almost abolished as a result of disturbances in the chloroplasts. After transferring the plants to 20/15°C P_n33 recovered completely within a few days. Woody plants hardened at temperatures around 0°C tolerated – 15 to ?36°C: P_n33 was reduced by 25 to 60% and hardly recovered at 20/15°C. Hardening at ?10°C induced a tolerance of ?32 to n33 was almost totally blocked, but at 20/15°C it returned to the values of the plants hardened at 0°C within a few days. In woody plants disturbances were invariably localized in the chloroplasts. Thus, conifers, and especially Pinus cembra, can survive much lower temperatures than herbaceous plants and, at the same level of freezing tolerance, exhibit appreciably less restriction in relative P_n33.     

Thermoregulation dynamics in commercially reared colonies of the bumblebee Bombus terrestris

Thermoregulation, that is, the active control of temperature, is key to ensure proper brood development in both wild and captive bumblebee nests. In this study, thermoregulation dynamics were assessed relative to colony age and ambient temperature using commercially reared Bombus terrestris L. (Hymenoptera, Apidae, Bombus) colonies. We observed a positive relationship between brood and nest temperatures in response to ambient temperature. Thermoregulation investment (by either brooding or fanning) was lowest at brood surface temperatures between 33 and 34 °C and ambient temperatures between 28 and 32 °C. Brood temperature was less stable and thermoregulation investment higher in younger colonies, especially at lower ambient temperatures. Furthermore, queens initiated colonies sooner and colonies developed faster when kept at an ambient temperature of 29 °C as compared to 24 °C. Our results suggest that ambient temperatures are ideally kept between 29 and 31 °C.     

Neurotensin and bombesin: differential effects on body temperature of mice after intracisternal administration

Intracisternal administration of neurotensin or bombesin produces a significant hypothermic response in rodents in an ambient temperature of 23°C or below; bombesin has been reported to produce a significant hyperthermic response in rats at 36°C, but no change in colonic temperature at ambient temperatures between 31 and 33°C. In this study we compared the effects of the two neuropeptides on colonic temperature of mice exposed to different ambient temperatures to determine whether neurotensin also produces a poikilothermic state. From a series of experiments conducted at ambient temperatures of 4, 23, 26, 30, 34 and 38°C, in which mice received an intracisternal injection of an equimolar dose (0.6 nmol) of neurotensin or bombesin (or vehicle), we noted that the two neuropeptides produce different effects on colonic temperature. At ambient temperatures of 26°C and below, both neurotensin and bombesin produce a significant hypothermic response; however, at higher temperatures bombesin has no effect (30°C) or produces hyperthermia (34°C). In contrast, neurotensin produces hypothermia at 30°C and no significant effect at 34 and 38°C. In addition, a wide range of doses of neurotensin failed to produce the poikilothermic effects characteristic of centrally administered bombesin.     

Survival of tissue culture cells frozen by a two-step procedure to -196 degrees C. I. Holding temperature and time.

A two-step freezing procedure has been examined in order to separate some of the causes of damage following freezing and thawing. Different holding temperatures and times have been studied during the freezing of Chinese hamster tissue culture cells in dimethyl sulphoxide (5%, $\text{v}\text{v}$). Damage following rapid cooling to, time at, and thawing from different holding temperatures was found to increase at lower holding temperatures and at longer times. Damage on subsequent cooling from the holding temperature to ?196 °C and thawing was found to diminish at lower holding temperatures and longer times. The net result was that optimal survival from ?196 °C was obtained after 10 min at ?25 °C. Protection against the second step of cooling to ?196 °C was acquired at the holding temperature itself and was absent at ?15 °C without freezing.It seems that this technique will allow the different phases of freezing injury to be separated. These phases may include thermal shock to the holding temperature, hypertonic damage at the holding temperature and dilution shock on thawing from ?196 °C.     

Changes in Ambient Temperature Trigger Yawning But Not Stretching in Rats

Yawning appears to be involved in arousal, state change, and activity across vertebrates. Recent research suggests that yawning may support effective changes in mental state or vigilance through cerebral cooling. To further investigate the relationship between yawning, state change, and thermoregulation, 12 Sprague–Dawley rats (Rattus norvegicus) were exposed to a total of 2 h of ambient temperature manipulation over a period of 48 h. Using a repeated measures design, each rat experienced a range of increasing (22°C → 32°C), decreasing (32°C → 22°C), and constant temperatures (22°C; 32°C). Yawning and locomotor activity occurred most frequently during initial changes in temperature, irrespective of direction, compared to more extended periods of temperature manipulation. The rate of yawning also diminished during constant high temperatures (32°C) compared to low temperatures (22°C). Unlike yawning, however, stretching was unaffected by ambient temperature variation. These findings are compared to recent work on budgerigars (Melopsittacus undulatus), and the ecological selective pressures for yawning in challenging thermal environments are discussed. The results support previous comparative research connecting yawning with arousal and state change, and contribute to refining the predictions of the thermoregulatory hypothesis across vertebrates.     

Der Einfluß der Umgebungstemperatur auf Motilität,Körpertemperatur und Sauerstoffverbrauch von normalen und Pervitin-behandelten Mäusen

Single mice were kept in various ambient temperatures (15° to 35° C) and motility, oxygen consumption, and body temperature were recorded. Untreated animals: Motility was least at 25° C room temperature. Relations between motility and body temperature were linear at all ambient temperatures. The body temperatures of very agile mice did not vary at ambient temperatures from 15° to 30° C whereas that of quiet mice was strongly influenced by the milieu. The relations between oxygen consumption and body weight were also linear at all ambient temperatures; the corresponding regression coefficients decreased progressively with rising ambient temperatures. Oxygen consumption increased at a constant rate with motility, independent of ambient temperatures. Animals treated with methamphetamine: The LD₅₀ of methamphetamine decreased considerably with rising ambient temperature. The influence on body temperature of methamphetamine was very variable and depended on both dose and ambient temperature. Toxic doses of methamphetamine induced hyperthermia in warm surroundings and hypothermia in a cool milieu. Under the influence of methamphetamine, oxygen consumption increased or decreased considerably with the body temperature. Ambient temperatures exerted an essential influence on the cause of death after toxic doses of methamphetamine.     

Diurnal foraging‐mode shifts and food availability in nectarivore assemblages during winter

Abstract Temporal fluctuations of food resources and foraging activities have been studied extensively, especially at longer timescales (monthly, seasonally, among years). However, short‐term variation (e.g. within days) is less well understood. Here we systematically quantified diurnal patterns of foraging by nectarivorous birds (meliphagid honeyeaters) that numerically dominated stands of a winter‐flowering eucalypt, the red ironbark, Eucalyptus tricarpa, in central Victoria, Australia. Diurnal variation in food resources also was measured. Data were collected in winter. Anecdotal observations that honeyeaters change from almost exclusive nectarivory early in the day to a higher fraction of insectivory – especially aerial hawking – later in the day were confirmed, although in areas of high flowering intensity, nectar‐feeding remained the dominant foraging activity throughout the day. Local climatic factors (ambient temperature, windiness and cloud cover) all varied systematically through the day. Together, results were consistent with a change in foraging emphasis to greater insectivory as a function of elevated activities of insects (especially aerial ones), which was probably fostered by higher ambient temperatures. Contrary to energetic expectations, the nectarivores were very active early in the morning when ambient temperatures averaged approximately 3°C, well below thermoneutral temperatures. We deduced that the potential benefits of gathering as much energy‐rich nectar as possible before it was depleted outweighed the high costs of activities at low temperatures.