Modelling of temperature effects on batch microbial transglutaminase fermentation with Streptoverticillium mobaraense

Batch transglutaminase (MTG) fermentations by Streptovertivillium mobaraense WSH-Z2 at various temperatures ranging from 25 to 35 °C were studied. Dry cell weight and MTG activity could reach their maximal values of 25.1 g/l and 2.94 U/ml, respectively at 30 °C. One typical equation was used to describe the relationship between specific growth rate and culture temperature by comparing several typical equations. Different lag time was observed under various culture temperature. The low lag time was observed under high culture temperature. X = –a ₀(T – T ₀)² + X ₁ + a ₁ (1 – exp(a ₂ (T – T ₁))) and U = –a ₀ (T – T ₀ )² + U ₀ + a ₁ (1 – exp(a ₂ (T – T ₁ ))) could be used to describe the relationship between temperature and the maximal dry cell weight as well as the maximal MTG activity at each temperature.     

Thermal responses and survival after heat exposure are modulated by maintained differences in body temperature in mice

When individual mice were examined, it was found that the colonic body temperatureT _col of each individual within a genetically heterogeneous population tended to remain either above (warm) or below (cool) the population mean.T _col of warm, but not cool, mice showed circadian variation. When exposed to aT _a of 43° C, theT _col of cool mice increased by as musch as 2.4° C more than that of warm mice for a given 15 min increment of heating at 43°C. Survival of mice after acute lethal heat load (LD₇₅, –45°C) was significantly inversely correlated withT _col. Small persistent differences in body temperature of individuals may indicate differing thermal adaptedness.     

Life in extreme environments: Investigations on the ecophysiology of a desert bird,the Australian Diamond Dove (Geopelia cuneata Latham)

Summary The Diamond Dove, Geopelia cuneata, is the world's second smallest (ca. 35 g) species of the columbid order. The Diamond Dove is endemic in the arid and semiarid Mulga and Spinifex regions of Central and Western Australia. It regularly encounters ambient temperatures (T _a ) in its habitat above +40° C, especially when foraging for seeds on bare ground cover, and may be found at up to 40 km from water. This entails extreme thermal stress, with evaporative cooling constrained by limited water supply. Energy metabolism (M), respiration, body temperature (T _a ) and water budget were examined with regard to physiological adaptations to these extreme environmental conditions. The zone of thermal neutrality (TNZ) extended from +34° C to at least +45° C. Basal metabolic rate (BMR) was 34.10±4.19 J g^–1h^–1, corresponding to the values predicted for a typical columbid bird. Thermal conductance (C) was higher than predicted. Geopelia cuneata showed the typical breathing pattern of doves, a combination of normal breathing at a stable frequency (ca. 60 min^–1) at low T _a and panting followed by gular flutter (up to 960 min^–1) at high T _a . At T _a > +36° C, T _a increased to considerably higher levels without increasing metabolic rate, i.e. Q₁₀=1. This enabled the doves not only to store heat but also to save the amout of water that would have been required for evaporative cooling if T _a had remained constant. The birds were able to dissipate more than 100% of the metabolic heat by evaporation at T _a +44° C. This was achieved by gular flutter (an extremely effective mechanism for evaporation), and also by a low metabolic rate due to the low Q₁₀ value for metabolism during increased T _b . At lower T _a , Geopelia cuneata predominantly relied on non-evaporative mechanisms during heat stress, to save water. Total evaporative water loss over the whole T _a range was 19–33% lower than expected. In this respect, their small body size proved to be an important advantage for successful survival in hot and arid environments.Abbreviations and units Body Mass W (g) - Ambient Temperature T _a (°C) - Body Temperature T _b (°C) - Thermoneutral Zone (TNZ) - Metabolism M (J g^–1 h^–1) - Thermal Conductance C - wet Thermal Conductance C _wet (J g^–1 h^–1 °C^–1) - Evaporative Water Loss EWL (mg H₂O g^–1 h^–1) - Evaporative Heat Loss EHL (J g^–1 h^–1) - Breathing Frequency F (breaths min^–1) - Tidal Volume V _t (ml breath^–1) - Standard Temperature Pressure Dry STPD - Body Temperature Pressure Saturated BTPS - Respiratory Quotient RQ - n.s. not significant (P>0.05) - n number of experiments     

Heat balance of two starling species (Sturnus vulgaris andOnychognathus tristrami) from temperate and desert habitats

Summary Body temperature (T _b), oxygen consumption , thermal conductance (C) and evaporative water loss (EWL) were measured at various air temperatures (T _a) in two starlings which evolved in the tropics: a migratory species from a temperate climate,Sturnus vulgaris, and a resident, desert species,Onychognathus tristrami (Aves, Passeriformes, Sturnidae).AtT _a's of 4–35°C both birds hadT _b of 40.6°C. At 44°C,T _b ofSturnus was 45.8°C and that ofOnychognathus 43.3°C.T _a of 44°C was tolerated only byOnychognathus. The thermoneutral zone (TNZ) ofSturnus was in theT _a range of 29.5°C–36.5°C, that ofOnychognathus 21.5–36.5°C. ofSturnus within its TNZ (BMR) was 2.37 ml O₂ g^–1 h^–1, which is close to the expected BMR; that ofOnychognathus, 1.67 ml O₂ g^–1 h^–1, is only 74% of the expected. AtT _a'sNZ,C ofSturnus was twice as high as that ofOnychognathus and 1.68 times the expected value, whereasC ofOnychognathus was only 94% of the expected. At highT _a'sOnychognathus had higherC thanSturnus. At either low or highT _a's EWL ofSturnus was greater than ofOnychognathus.The responses shown bySturnus are typical of a tropical bird living in a moderate environment. This indicates that neither in USSR where it spends the summer, nor in Israel where it spends the winter, is this starling exposed to extreme temperatures.Onychognathus is better adapted not only to high but also to the low temperatures prevailing in mountainous regions of the desert.Symbols and abbreviations BMR basal metabolic rate - C thermal conductance - EWL evaporative water loss - HE evaporative heat loss - HP heat production - TNZ thermoneutral zone     

Effects of ambient temperature and altitude on ventilation and gas exchange in deer mice (Peromyscus maniculatus)

Summary The effects of different ambient temperatures (T _a) on gas exchange and ventilation in deer mice (Peromyscus maniculatus) were determined after acclimation to low and high altitude (340 and 3,800 m).At both low and high altitude, oxygen consumption ( ) decreased with increasingT _a atT _a from –10 to 30 °C. The was 15–20% smaller at high altitude than at low altitude atT _a below 30 °C.Increased atT _a below thermoneutrality was supported by increased minute volume ( ) at both low and high altitude. At mostT _a, the change in was primarily a function of changing respiration frequency (f); relatively little change occurred in tidal volume (V _T) or oxygen extraction efficiency (O₂EE). AtT _a=0 °C and below at high altitude, was constant due to decliningV _T and O₂EE increased in order to maintain high .At high altitude, (BTP) was 30–40% higher at a givenT _a than at low altitude, except atT _a below 10 °C. The increased at high altitude was due primarily to a proportional increase inf, which attained mean values of 450–500 breaths/min atT _a below 0 °C. The (STP) was equivalent at high and low altitude atT _a of 10 °C and above. At lowerT _a, (STPD) was larger at low altitude.At both altitudes, respiratory heat loss was a small fraction (<10%) of metabolic heat production, except at highT _a (20–30 °C).Abbreviations EHL evaporative heat loss - f respiration frequency - HL _a heat loss from warming tidal air - HL _e evaporative heat loss in tidal air - HL total respiratory heat loss - MHP metabolic heat production - O ₂ EE oxygen extraction efficiency - RQ respiratory quotient - T _a ambient temperature - T _b body temperatureT _lc lower critical temperature - carbon dioxide production - evaporative water loss - oxygen consumption - minute volume - V _T tidal volume     

Thermoregulation,gas exchange,and ventilation in Adelie penguins (Pygoscelis adeliae)

Summary Adelie penguins (Pygoscelis adeliae) experience a wide range of ambient temperatures (T _a) in their natural habitat. We examined body temperature (T _b), oxygen consumption ( ), carbon dioxide production ( ), evaporative water loss ( ), and ventilation atT _a from –20 to 30 °C. Body temperature did not change significantly between –20 and 20°C (meanT _b=39.3°C).T _b increased slightly to 40.1 °C atT _a=30°C. Both and were constant and minimal atT _a between –10 and 20°C, with only minor increases at –20 and 30°C. The minimal of adult penguins (mean mass 4.007 kg) was 0.0112 ml/[g·min], equivalent to a metabolic heat production (MHP) of 14.9 Watt. The respiratory exchange ratio was approximately 0.7 at allT _a. Values of were low at lowT _a, but increased to 0.21 g/min at 30°C, equivalent to 0.3% of body mass/h. Dry conductance increased 3.5-fold between –20 and 30°C. Evaporative heat loss (EHL) comprised about 5% of MHP at lowT _a, rising to 47% of MHP atT _a=30°C. The means of ventilation parameters (tidal volume [VT], respiration frequency [f], minute volume [I], and oxygen extraction [ ]) were fairly stable between –20 and 10°C (VT did not change significantly over the entireT _a range). However, there was considerable inter- and intra-individual variation in ventilation patterns. AtT _a=20–30°C,f increased 7-fold over the minimal value of 7.6 breaths/min, and I showed a similar change. fell from 28–35% at lowT _a to 6% atT _a=30°C.Abbreviations C thermal conductance - EHL evaporative heat loss - oxygen extraction - f respiratory frequency - MHP metabolic heat production - evaporative water loss - LCT lower critical temperature - RE respiratory exchange ratio - T _a ambient temperature - T _b body temperature - rate of oxygen consumption - rate of carbon dioxide production - I inspiratory minute volume - VT tidal volume     

Regulation of local sweating in sleep-deprived exercising humans

Thermoregulatory sweating [total body (m _sw,b), chest (m _sw,c) and thigh (m _sw,t) sweating], body temperatures [oesophageal (T _oes) and mean skin temperature (T _sk)] and heart rate were investigated in five sleep-deprived subjects (kept awake for 27 h) while exercising on a cycle (45 min at approximately 50% maximal oxygen consumption) in moderate heat (T _air andT _wall at 35° C. Them _sw,c andm _sw,t were measured under local thermal clamp (T _sk,1), set at 35.5° C. After sleep deprivation, neither the levels of body temperatures (T _oes,T _sk) nor the levels ofm _{sw, b},m _{sw, c} orm _{sw, t} differed from control at rest or during exercise steady state. During the transient phase of exercise (whenT _sk andT _sk,1 were unvarying), them _{sw, c} andm _{sw, t} changes were positively correlated with those ofT _oes. The slopes of them _{sw, c} versusT _oes, orm _{sw, t} versusT _oes relationships remained unchanged between control and sleep-loss experiments. Thus the slopes of the local sweating versusT _oes, relationships (m _{sw, c} andm _{sw, t} sweating data pooled which reached 1.05 (SEM 0.14) mg·cm^–2·min^–1°C^–1 and 1.14 (SEM 0.18) mg·cm^–2·min^–1·°C^–1 before and after sleep deprivation) respectively did not differ. However, in our experiment, sleep deprivation significantly increased theT _oes threshold for the onset of bothm _{sw, c} andm _{sw, t} (+0.3° C,P<0.001). From our investigations it would seem that the delayed core temperature for sweating onset in sleep-deprived humans, while exercising moderately in the heat, is likely to have been due to alterations occurring at the central level.     

Energy metabolism,body-temperature and breathing parameters in nontorpid blue-naped mousebirdsUrocolius macrourus

Summary Breathing frequencyF _r of resting blue-naped mousebirdsUrocolius macrourus lies between 50–70 per min and correlates directly with ambient temperatureT _a and energy metabolismM. The nocturnal mean energy intake per breath varies between 5.6–17.7 mJ/g. At highT _a the birds show gular fluttering with a relatively constantF _r of about 460 min^–1.M shows a constant absolute day-night difference of 25 J/g·h; the relative differences areT _a-dependent between 36–168% (lower values at lowerT _a). Thermal conductance is 2.10–2.15 J/g·h·°C (predicted 2.67), indicating a good insulation. Basal metabolic rate BMR is reduced by 63% compared to predicted values. At aT _a-range of +8–36 °C the birds are normothermic. Below this range nocturnalT _b andM decrease slightly with fallingT _a. The birds show partial heterothermia (shallow hypothermia). Clustering is an effective energy saving strategy which allows loweringM with keeping highT _b even at lowT _a.Oxygen-intake is controlled byF _r as well as by tidal volumeV t inT _a-dependent changing portions.V T can vary between 0.29–0.91 ml (mean value 49.7 ml).Abbreviations T _a ambient temperature - T _b body temperature - M energy metabolism - F _r breathing frequency - V T tidal volume - BMR basal metabolic rate - TNP thermoneutral point     

Thermoregulation of water foraging wasps (Vespula vulgaris and Polistes dominulus)

A comparison of the thermoregulation of water foraging wasps (Vespula vulgaris, Polistes dominulus) under special consideration of ambient temperature and solar radiation was conducted. The body surface temperature of living and dead wasps was measured by infrared thermography under natural conditions in their environment without disturbing the insects’ behaviour. The body temperature of both of them was positively correlated with T_a and solar radiation. At moderate T_a (22–28 °C) the regression lines revealed mean thorax temperatures (T_th) of 35.5–37.5 °C in Vespula, and of 28.6–33.7 °C in Polistes. At high T_a (30–39 °C) T_th was 37.2–40.6 °C in Vespula and 37.0–40.8 °C in Polistes. The thorax temperature excess (T_th–T_a) increased at moderate T_a by 1.9 °C (Vespula) and 4.4 °C (Polistes) per kW⁻¹ m⁻². At high T_a it increased by 4.0 °C per kW⁻¹ m⁻² in both wasps. A comparison of the living water foraging Vespula and Polistes with dead wasps revealed a great difference in their thermoregulatory behaviour. At moderate T_a (22–28 °C) Vespula exhibited distinct endothermy in contrast to Polistes, which showed only a weak endothermic activity. At high T_a (30–39 °C) Vespula reduced their active heat production, and Polistes were always ectothermic. Both species exhibited an increasing cooling effort with increasing insolation and ambient temperature.     

Responses to heat stress in two species of Australian quail,Coturnix pectoralis andCoturnix chinensis

Summary Stubble quail and King quail are both native to Australia although Stubble quail extend into more arid environments than do King quail. In this study, the responses of body temperature (T _b), heart rate (f _h), respiration rate (f _r) and rates of gular flutter (f _g) were measured in response to ambient temperatures (T _a) ranging from 20 °C to 50 °C. Both species exhibited hyperthermia atT _a in excess of 38–39 °C although both species maintainedT _b lower thanT _a atT _a above 42 °C. Respiration rate remained relatively constant until the onset of panting, just prior to the commencement of gular flutter. The onset of panting and gular flutter in both species was relatively sudden and occurred at a meanT _a of 38.1 °C for Stubble quail (meanT _b of 42.5 °C) and a significantly higherT _a of 40.9 °C but similar meanT _b of 42.1 °C for King quail. Gular flutter appeared to occur synchronously with respiration and showed some tendency to increase withT _b. The percentage of time spent in gular flutter showed a direct increase withT _b. Heart rate tended to decrease with increasingT _a in King quail while remaining relatively constant in Stubble quail. However, the relationship was not consistent and a great deal of variability existed between individuals. The two species are similar in their responses to heat stress and in general these responses do not reflect their different natural habitats.Symbols f _h heart rate - f _r respiratory rate - f _g rate of gular fluttering     

Metabolic and thermoregulatory responses to heat and cold in the Djungarian hamster,Phodopus sungorus

Summary Djungarian hamsters,Phodopus sungorus (31.1 g body weight) were exposed to ambient temperatures (T _a ) between –35°C and +34°C. They tolerated severe cold stress but were less able to withstand heat. At –35° CT _a , normal body temperature was maintained for several hours. Thereby maximum thermal insulation was calculated at 1.1 g·°C/mW, which is only slightly higher than expected from the hamsters body size. High levels of heat production (60 to 90 m W/g) were maintained for several hours, suggesting that well developed means of heat production are the main reason for cold tolerance of the Djungarian hamster.     

Effects of wind on thermoregulation and energy balance in deer mice (Peromyscus maniculatus)

Summary The effects of various convective and temperature regimes on heat production, evaporative heat loss, and thermal resistance were studied in deer mice,Peromyscus maniculatus. Heat production (measured as oxygen consumption) increased with increasing wind speed (V) and decreasing ambient temperature (T _a), except atT _a=35°C which was thermoneutral for allV from 0.05 through 3.75 m/s. Evaporative water loss ( ) increased with increasingT _a, but wind had little effect on except at highT _a. In the absence of forced convection, the animals' total resistance to heat transfer (r _t) was high and stable atT _a below thermoneutrality. However, at highV ther _t increased steadily with decreasingT _a. Although deer mice rarely experience high wind speeds in natural microhabitats, the convective regime is nevertheless important in determining rates of heat loss, and must be considered in studies of ecological energetics.Symbols and Abbreviations A animal surface area - HP _n net metabolic heat production - EHL evaporative heat loss - MHP metabolic heat production - r _t total resistance to heat transfer - r _ext external resistance component of r_t - RQ respiratory quotient - pc _p volumetric specific heat of air - T _a ambient temperature - t _b body temperature - t _e operative, or equivalent blackbody temperature of the environment - T _sk skin temperature - T _es standard operative temperature - V wind speed - oxygen consumption - carbon dioxide production - evaporative water loss     

Oxygen consumption and flight muscle activity during heating in workers and drones of Apis mellifera

Summary Instantaneous oxygen consumption, muscle potential frequency, thoracic and ambient temperature were simultaneously measured during heating in individual workers and drones of honey bees. Relationships between these parameters and effects of thoracic temperature on power input and temperature elevation were studied. Oxygen consumption increased above basal levels only when flight muscles became active. Increasing muscle potential frequencies correlated with elevated oxygen consumption and raised thoracic temperature. The difference between thoracic and ambient temperature and oxygen consumption were linearly related. Oxygen consumption per muscle potential (l O₂ · g _–1 ^thorax · MP^–1) was two-fold higher in drones than in workers. However, oxygen consumption for heating the thorax (l O₂ · g _–1 ^thorax · (T_th-T_a) · °C^–1) was nearly the same in workers and drones. Thoracic temperature affected the amount of oxygen consumed per muscle potential (R₁₀=1.5). Achieved temperature elevation per 100 MP was more temperature sensitive in drones (R₁₀=6–10) than in workers (R₁₀=3.6). Q₁₀ values for oxygen consumption were 3 in workers and 4.5–6 in drones. Muscle potential frequency decreased with a Q₁₀=1.8 in workers and 2.7 in drones. Heating behaviour of workers and drones was different. Drones generated heat less continuously than workers, and showed greater interindividual variability in predilection to heat. However, the maximal difference between ambient and thoracic temperature observed was 22 °C in drones and 14 °C in workers, indicating greater potential for drones.Abbreviations DL dorsal-longitudinal muscle - DV dorsoventral muscle - MP muscle potential - T _a ambient temperature - T _th thoracic temperature     

Ventilatory physiology of the numbat (<Emphasis Type="Italic">Myrmecobius fasciatus</Emphasis>)

This study examines the ventilatory physiology of the numbat (Myrmecobius fasciatus), a small to medium-sized (550 g) termitivorous marsupial. Ventilatory parameters at thermoneutrality reflect the slightly low (83% of predicted) basal metabolic rate of the numbat, with ventilation frequency (ƒ_R; 30.6±3.65 breaths min^–1), tidal volume [V_T; 6.0±0.66 ml at body temperature and pressure, saturated (BTPS)] and consequently minute volume (V_I; 117.7±15.22 ml min^–1; BTPS) all being 80–87% of that expected for a marsupial of similar body mass. Oxygen extraction was 27.7±1.37% in the thermoneutral zone. As is typical of marsupials, numbats accommodated increased oxygen consumption rates at ambient temperatures (T _a) below the thermoneutral zone by increasing minute volume (up to 411.2±43.98 ml min^–1; BTPS at T _a=10 °C) rather than oxygen extraction. Minute volume at 10 °C increased more by changes in ventilation frequency (up to 45.5±4.85 breaths min^–1) than tidal volume (9.4±1.03 ml, BTPS), as is also typical for a small-medium sized marsupial.Abbreviations BMR basal metabolic rate - BTPS body temperature and pressure, saturated - EO ₂ oxygen extraction - ƒ _R ventilation frequency - STPD standard temperature and pressure, dry - T _a ambient temperature - T _b body temperature - TNZ thermoneutral zone - V _I minute volume - V _T tidal volume - O ₂ oxygen consumption rate Communicated by I.D. Hume     

Cold thermoregulatory changes induced by sleep deprivation in men

The aim of this study was to evaluate the thermoregulatory changes induced by 27-h of sleep deprivation (SD) in men at rest both in a comfortable ambient temperature and in cold air. A group of 12 male subjects were placed in a comfortable ambient temperature (dry bulb temperature,T _db = 25° C, relative humidity, rh = 40%–50% , clothing insulation = 1 clo) for 1 h and then they were submitted to a standard cold air test in a climatic chamber for 2h (T _db=1° C, rh = 40%–50%, wind speed = 0.8 m·s^–1, nude), before and after 27 h of sleep deprivation. Thermoregulatory changes (rectal temperature,T _re; mean skin temperature, _sk; metabolic heat production ) were monitored continuously. At comfortable ambient temperature, no significant change was observed after SD forT _re, _sk and . During the cold test,T _re did not change but _sk and were higher after SD (P<0.05). Increased (+ 6%,P < 0.05) was related to earlier and higher shivering, with a possible increase in the sensitivity of the thermoregulatory system as shown by the shorter time to onset of continous shivering (d): 8.66 (SEM 1.33) min versus 28.20 (SEM 1.33) min (P < 0.001) and by a higher _sk observed at d: 27.60 (SEM 1.40)° C versus 21.40 (SEM 0.60)° C (P < 0.001). These results were associated with higher cold sensations and shivering following SD. They also suggested that SD modified thermoregulatory responses at a central level especially in a cold environment.     

Exchange of HCO 3 − for monovalent anions across the human erythrocyte membrane

Summary A stopped-flow rapid reaction apparatus was used for measuring changes in extracellular pH (pH _o ) of red cell suspensions under conditions wheredpH _o /dt was determined by the rate of HCO ₃ ^– /X ^– exchange across the membrane (X ^–=Cl^–, Br^–, F^–, I^–, NO ₃ ^– or SCN^–). The rate of the exchange at 37°C decreased forX ^– in the order: Cl^–>Br^–>F^–>I^–>NO ₃ ^– >SCN^–, with rate constants in the ratios 10.860.770.550.520.31. When HCO ₃ ^– is exchanged for Cl^–, Br^–, F^–, NO ₃ ^– or SCN^–, a change in the rate-limiting step of the process takes place at a transition temperature (T _T ) between 16 and 26°C. In I^– medium, however, no transition temperature is detected between 3 and 42°C. AlthoughT _T varies withX ^–, the activation energies both above and belowT _T are similar for Cl^–, Br^–, NO ₃ ^– and F^–. The values of activation energy are considerably higher whenX ^–=I^– or SCN^–. The apparent turnover numbers calculated for HCO ₃ ^– /X ^– exchange (except forX ^–=I^–) at the correspondingT _T ranged from 140 to 460 ions/site ·sec for our experimental conditions. These findings suggest that: (i) HCO ₃ ^– /X ^– exchange for allX ^– studied takes place via the rapid anion exchange pathway; (ii) the rate of HCO ₃ ^– /X ^– exchange is influenced by the specific anions involved in the 11 obligatory exchange; and (iii) the different transition temperatures in the Arrhenius diagrams of the HCO ₃ ^– /X ^– exchange do not seem to be directly related to a critical turnover number, but may be dependent upon the influence ofX ^– on protein-lipid interactions in the red blood cell membrane.     

Pigeon flight in a wind tunnel

Summary Core temperatureT _c, breast temperatureT _s–br and leg temperatureT _s–1 were measured simultaneously in pigeons during rest and flight in a wind tunnel, using thermistors.MeanT _c at rest is 39.8±0.7°C and is independent of ambient temperatureT _a (10–30°C). In the first minutes of flight,T _c increases to 1.5–3.0°C above resting level and remains at this higher level. This hyperthermia increases withT _a (v=const.). It is±constant in the lowT _a range (10.6–13.9°C) at flight speeds v ranging from 10–18 m s^–1 and normal body mass, but increases with v and elevated body mass in the highT _a range (23.7–28.8°C). T _s–1 is adapted toT _a at rest and increases in flight up to 3–4°C belowT _c. This increase inT _s–1 is linear toT _a. T _s–br is always lower thanT _c, in extreme cases reaching restingT _c in flight.Supported by the Deutsche Forschungsgemeinschaft     

Body temperatures during rest and exercise in residents and sojourners in hot climate

Rectal (T_re), mean skin temperature ( _sk) and sweating rate ( ) were measured in 4 residents of temperate climate under acute moderate heat exposure (designated EE in such an experimental situation), after 3 weeks in India (designated as EI) and in 8 Indian residents (designated as II) both at rest and during submaximal exercises at 2 different intensities. At rest, T_re is higher in EI (37.6°C) than in EE (36.8°C, P<0.01) and reaches 37.8°C in II. At the end of exercise, the increment in T_re seems to depend on work load only and to be independent of thermal environment; S follows a similar pattern in the 3 groups of subjects: _sk is altered neither by exercise nor acclimatization. Under chronic heat exposure compared to acute conditions: (1) identical is achieved with higher T_re and similar _sk so that the linear relationships vs T_re is shifted to the right. (2) the T_re — _sk difference is greater at rest and during exercise: hence, skin blood flow, calculated from heat balance equation diminishes. In hot climate, a rise in T_re seems to be an adaptive response which allows the body to reduce skin blood flow.     

Influence of soil temperature on methane emission from rice paddy fields

Methane emission rates from an Italian rice paddy field showed diel and seasonal variations. The seasonal variations were not closely related to soil temperatures. However, the dieL changes of CH₄ fluxes were significantly correlated with the diel changes of the temperature in a particular soil depth. The soil depths with the best correlations between CH4 flux and temperature were shallow (1–5cm) in May and June, deep (10–15cm) in June and July, and again shallow (1–5 cm) in August. Apparent activation energies (E_a) calculated from these correlations using the Arrhenius model were relatively low (50–150 kJ mol^–1) in May and June, but increased to higher values (80–450 kJ mol^–1) in August. In the laboratory, CH₄ emission from two rice cultures incubated at temperatures between 20 and 38°C showed E . values of 41 and 53 kJ mol^–1) Methane production in anoxic paddy soil suspensions incubated between 7 and 43°C showed E values between 53 and 132 kJ mol^–1 with an average value of 85 kJ mol^–1) and in pure cultures of hydrogenotrophic methanogenic bacteria E _a values between 77 and 173 (average 126) kJ mol^–1. It is suggested that diel changes of soil properties other than temperature affect CH₄ emission rates, e.g. diel changes in root exudation or in efficiency of CH⁴ oxidation in the rhizosphere.     

The effect of ambient temperature on the relationship between ventilation and metabolism in a small parrot (Agapornis roseicollis)

Summary Values for basal metabolism, standard tidal volume (V _T), standard minute volume ( ), and mean extraction efficiency (EO₂) in the thermal neutral zone (TNZ) inAgapornis roseicollis (1.84 ml·min^–1; 0.95 ml·br^–1, STPD; and 33.3 ml·min^–1, STPD; and 22.5%; respectively) were all very similar to values for these parameters previously measured inBolborhynchus lineola, a similarly sized, closely related species from a distinctly different habitat.Having both a lower critical temperature (T_lc) below and an upper critical temperature (T_uc) above those ofB. lineola, the TNZ ofA. roseicollis extended from 25° to at least 35°C. The thermal conductance below the TNZ ofA. roseicollis was 14% less than that ofB. lineola. Therefore, at 5°C the standard metabolic rate (SMR) of the former is 17% less than that of the latter, and at 35°C it is 20% less. At 5°CA. roseicollis has a lower EO₂ and at 35°C a higher EO₂ than that ofB. lineola. The patterns of resting energy metabolism and of ventilation ofA. roseicollis and ofB. lineola are consistent with the former species being better suited to living in a more variable thermal environment than the latter.MeanV _T has a weak positive correlation with the rate of oxygen consumption ( ) at a constant ambient temperature (T _a) but a much stronger correlation when resting increases in response to a decrease inT _a.V _t is the only ventilatory parameter which is linearly correlated toT _a from 35° to –25°C. The data suggest thatT _a may have a regulatory effect onV _T somewhat independent of or .