The Influence of Temperature on the Content of Liver Glycogen and Muscle Glycogen in Sparrow

The sparrows for experimental materials were divided into 5 °C acclimation group, 30 °C acclimation group and control group. The content of liver glycogen and muscle glycogen were measured with sulfuric acid-anthrone colorimetric method after two weeks of acclimation. The results show that: When the temperature is 5 °C, the glycogen content was very significantly lower than the glycogen content of control group (p0.05); The change in glycogen content was extremely significant between the two temperature (p<0.01).

Adaptation of exercise ventilation during an actively-induced hyperthermia following passive heat acclimation

Hyperthermia-induced hyperventilation has been proposed to be a human thermolytic thermoregulatory response and to contribute to the disproportionate increase in exercise ventilation (V̇e) relative to metabolic needs during high-intensity exercise. In this study it was hypothesized that V̇e would adapt similar to human eccrine sweating (ĖSW) following a passive heat acclimation (HA). All participants performed an incremental exercise test on a cycle ergometer from rest to exhaustion before and after a 10-day passive exposure for 2 h/day to either 50°C and 20% relative humidity (RH) ( n = 8, Acclimation group) or 24°C and 32% RH ( n = 4, Control group). Attainment of HA was confirmed by a significant decrease ( P = 0.025) of the esophageal temperature (Tes) threshold for the onset of ĖSW and a significantly elevated ĖSW ( P ≤ 0.040) during the post-HA exercise tests. HA also gave a significant decrease in resting Tes ( P = 0.006) and a significant increase in plasma volume ( P = 0.005). Ventilatory adaptations during exercise tests following HA included significantly decreased Tes thresholds ( P ≤ 0.005) for the onset of increases in the ventilatory equivalents for O2 (V̇e/V̇o2) and CO2 (V̇e/V̇co2) and a significantly increased V̇e ( P ≤ 0.017) at all levels of Tes. Elevated V̇e was a function of a significantly greater tidal volume ( P = 0.003) at lower Tes and of breathing frequency ( P ≤ 0.005) at higher Tes. Following HA, the ventilatory threshold was uninfluenced and the relationships between V̇o2 and either V̇e/V̇o2 or V̇e/V̇co2 did not explain the resulting hyperventilation. In conclusion, the results support that exercise V̇e following passive HA responds similarly to ĖSW, and the mechanism accounting for this adaptation is independent of changes of the ventilatory threshold or relationships between V̇o2 with each of V̇e/V̇o2 and V̇e/V̇co2.

Consequences of thermal acclimation for the mating behaviour and swimming performance of female mosquito fish

The mating system of eastern mosquito fish ( Gambusia holbrooki ) is dominated by male sexual coercion, where all matings are forced and females never appear to cooperate and actively avoid all attempts. Previous research has shown that male G. holbrooki offer a model system for examining the benefits of reversible thermal acclimation for reproductive success, but examining the benefits to female avoidance behaviour has been difficult. In this study, we examined the ability of non-male-deprived female G. holbrooki to avoid forced–coercive matings following acclimation to either 18 or 30°C for six weeks (12 h light : 12 h dark photoperiod). Thermal acclimation of burst and sustained swimming performance was also assessed, as these traits are likely to underlie their ability to avoid forced matings. There was no influence of thermal acclimation on the burst swimming performance of female G. holbrooki over the range 18–30°C; however, sustained swimming performance was significantly lower in the warm- than the cool-acclimation group. For mating behaviour, we tested the hypothesis that acclimation would enhance the ability of female G. holbrooki to avoid forced matings at their host acclimation temperature relative to females acclimated to another environment. However, our hypothesis was not supported. The rate of copulations was almost three times greater for females acclimated to 30°C than 18°C when tested at 30°C, indicating that they possess the ability to alter their avoidance behaviour to ‘allow’ more copulations in some environments. Coupled with previous studies, female G. holbrooki appear to have greater control on the outcome of coercive mating attempts than previously considered and can alter their propensity to receive forced matings following thermal acclimation. The significance of this change in female mating-avoidance behaviours with thermal acclimation remains to be explored.

The effects of increased protein intake on kidney size and function.

In endothermic vertebrates, long-term increases in metabolic energy demand are often associated with increases in food intake and accompanied by increases in organ mass. Wide-scale increases in organ mass have often been attributed to a metabolic response to increased energy intake and utilization. On a constant diet, however, increased food intake is also associated with increased protein intake. We hypothesized that, while increased food intake itself may be responsible for increases in digestive tract mass, the consequent increased protein intake would be the factor responsible for increased kidney mass and function. Thus, we exposed male and female mice to diets differing in protein level (7 %, 15 % or 46 % casein by mass) at different acclimation temperatures (5 degrees C or 23 degrees C). Within an acclimation temperature, food intake rate remained constant over the entire range of dietary protein level, and protein intake rate increased as dietary content increased. The mice in the cold-acclimation group increased food intake rate by 48-120 % over those in the warm-acclimation group. Liver, kidney and stomach mass increased with protein intake rate, while digestive tract and other vital organ masses increased only in response to increased energy intake rate. Blood urea nitrogen levels increased with protein intake rate. Glomerular filtration rates increased with increases in dietary protein level in male mice but not female mice. Finally nitrogen filtration rate increased with protein intake rate for mice on the high-protein diet. We suggest that it is primarily the increased protein intake rate rather than the increased food intake rate that results in the changes in kidney and liver mass and kidney function observed to occur in situations of high energy demand.

The Effects of Salinity Acclimation on the Osmotic Properties of Mitochondria from the Gill Of Crassostrea Virginica

Glutamate oxidation in mitochondria from the gills of oysters (Crassostrea virginica Gmelin) acclimated to sea water (SW) is sensitive to assay medium osmolanty. Compared to a medium of the osmolarity of sea water, decreasing osmolarity stimulates glutamate oxidation and increasing osmolarity inhibits glutamate oxidation. Glutamate oxidation by mitochondria from oysters acclimated to dilute sea water (DSW) is 2.5-fold greater than in SW animals when each is assayed under isosmotic conditions. The maximal rates obtained in both acclimation groups are equal. Although the DSW animals were acclimated to an osmolarity approximately 660 mosmol 1−1 lower than SW animals, the osmotic optimum was only 100–200 mosmol 1−1 lower in the former group. Isolation medium osmolarity does not affect the osmolarity at which the maximum rate of glutamate oxidation is observed in either acclimation group. A low-osmolarity isolation medium reduces the oxidation rates and quality of the mitochondria, as assessed by the respiratory control ratio in both acclimation groups. These data suggest that an optimal matrix solute concentration or ionic strength is required for maximal rates of glutamate oxidation rather than an optimal mitochondrial volume. The optimal mitochondrial matrix milieu can be achieved both by acclimation to dilute sea water and by incubation in hypo-osmotic media.

Protein kinase activity in liver of heat-acclimated hamsters

Protein kinase activity in incubated liver slices from 35 degrees C heat-acclimated (HA) hamsters was 70% higher than in similar slices from 23 degrees C control (C) hamsters. Adding glucagon to the incubation medium increased protein kinase activity by 65% in slices from C animals, but by only 30% in slices from HA animals. Binding of [3H]cAMP to proteins of a low-speed supernatant fraction of incubated and homogenized slices was 30% lower for HA than for C hamsters. For each acclimation group this binding was reduced 30% by incubation of the slices with glucagon. The activities of phosphorylase kinase, phosphorylase phosphatase, and phosphorylase alpha in slices incubated with or without glucagon did not differ between groups. Addition of glucagon increased phosphorylase kinase by 30% and phosphorylase alpha by 40% but caused no change in phosphorylase phosphatase activity. These results suggest that heat acclimation of the hamster increases the amount of a species of liver protein kinase that is different from the one that mediates the effect of glucagon on glycogenolysis.

Exercise training hypotension: implications for plasma volume, renin, and vasopressin

To determine the function of changes in plasma volume (PV), plasma renin activity (PRA), and arginine vasopressin (AVP) in the mechanism of the reduction of resting blood pressure during exercise training, resting supine, sitting, and standing systolic (SBP) and 5th-phase diastolic (DBP) blood pressures were measured in 10 men (19-24 yr) before and after an 8-day (2 h/day) training period on a cycle ergometer. The control group (5 men) exercised at 1.4 1/min [44% peak O2 uptake (VO2 max)] at 23.8 degrees C Tdb and 50% rh, and the acclimation group at 1.5 1/min (46% VO2 max) at 39.8 degrees C Tdb and 50% rh. After acclimation, resting supine and sitting DPB decreased (P less than 0.05) by 6 and 9 mmHg, respectively. There were no significant changes in DBP in the controls or in SBP in either group. After training, PV increased by 12.2% in controls and by 17.6% after acclimation. The resting hypotension could not be attributed to changes in resting levels of PV, AVP, or PRA. However, large decreases in PV and large increases in AVP and especially PRA during acclimation exposures suggest these responses may play a role in the chronic hypotensive response.

Noradrenaline-induced calorigenesis in warm- or cold-acclimated rats. In vivo estimation of adrenoceptor concentration of noradrenaline effecting half-maximal response

Desmethylimipramine (DMI, 1 mg DMI∙HCl kg−1) and normetanephrine (NMN, 1 μg min−1 g−0.74) were used to inhibit, respectively, neuronal and extraneuronal uptakes of noradrenaline (NA) during calorigenesis induced in barbital-sedated warm-acclimated (WA) or cold-acclimated (CA) rats by infusion of NA, a procedure which mimics the effects of NA released within calorigenic tissues in response to cold exposure. The doses of the inhibitors were selected for maximal effectiveness in potentiating calorigenic response and for minimal side effects. For rats of either acclimation group treated with DMI and NMN, with DMI only, or with neither inhibitor the doses of NA required to evoke approximately half-maximal calorigenic responses were, respectively, 0.5, 1.0, and 3.5 ng min−1 g−0.74. The corresponding steady-state concentrations of NA in arterial plasma averaged 14.3, 21.7, and 43.2 nM in the three groups of WA rats and 10.0, 14.8, and 31.9 nM in the three groups of CA rats. Reduction by NA uptake inhibitors of the circulating levels of NA necessary to stimulate calorigenesis, half-maximally, presumably in brown adipose tissue, indicates a reduction in the steepness of the NA concentration gradient between capillary plasma and synaptic clefts in that tissue. The steady-state concentration of NA in blood plasma of rats treated with DMI and NMN and infused with NA at a dose of 0.5 ng min−1 g−0.74 (~1 × 10−8 M) is a good estimate of the NA concentration required at calorigenic adrenoceptors to effect half-maximal activation. Presumably, this concentration is also an estimate of that resulting from NA released at nerve endings during cold-induced activation of nonshivering thermogenesis at half-maximal rates in brown adipose tissue.