Trade-off between energy budget, thermogenesis and behavior in Swiss mice under stochastic food deprivation

(1) The role of metabolic rate, thermogenesis and behavior in trade-off strategy was examined in Swiss mice under stochastic food deprivation (FD).

(2) For the mice under severe FD, food intake on feeding days increased, and basal metabolic rate (BMR) and nonshivering thermogenesis decreased significantly. The duration of activity decreased but resting behavior increased significantly on feeding days.

(3) It suggested that a trade-off between increased food intake and decreased energy expenditure related to lower BMR, thermogenesis and activity might be employed to meet reduced calorie intake caused by unpredictable FD.

Low-temperature tolerance of false codling moth Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa

(1) The low-temperature tolerance of false codling moth (FCM) Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a significant aspect of this pest's population dynamics and has implications for post-harvest control and sterile insect technique programs.

(2) Here, we report results of experiments examining the effects of time, temperature and their interactions on low-temperature tolerance in adult FCM. In addition, using a variety of thermal pre-treatments, we examine the potential for hardening responses over several hours to improve low-temperature tolerance in FCM.

(3) Lower lethal temperature assays showed significant effects of time, temperature and significant interactions between time and temperature on survival (p<0.0001 in all cases). The temperature at which the probability of survival of 50% of the FCM population after 2 h of exposure was −4.5 °C, which varied significantly to −0.5 °C in 10 h. Gender and early adult age did not affect low-temperature tolerance of FCM.

(4) Using a range of non-lethal, low- and high-temperature pre-treatments, FCM survival could not be increased (p>0.84) and thus limited evidence for rapid cold hardening was found. These results are discussed with respect to microclimate temperatures in typical FCM environments and have implications for understanding population dynamics in this species and the diversity of low-temperature responses of insects.

Bioenergetic responses of sub-adult sea cucumber Apostichopus japonicus (Selenka) (Echinodermata: Holothuroidea) to temperature with special discussion regarding its southernmost distribution limit in China

1. This paper investigated the bioenergetic responses of the sea cucumber Apostichopus japonicus (wet weights of 36.5±1.2 g) to different water temperatures (5, 10, 15, 20, 25 and 30 °C) in the laboratory.

2. Results showed that theoretically the optimal temperatures for energy intake and scope for growth (SFG) of sub-adult A. japonicus was at 15.6 and 16.0 °C, respectively. The aestivation threshold temperature for this life-stage sea cucumber could be 29.0 °C by taking feeding cessation as the indication of aestivation.

3. Our data suggests that A. japonicus is thermo-sensitive to higher temperature, which prevents it from colonising sub-tropical coastal zones. Therefore, water temperature plays an important role in its southernmost distribution limit in China.

4. The potential impact of global ocean warming on A. japonicus might be a northward shift in the geographical distribution.

Adaptation to oxidative stress and impact of chronic oxidative stress on immunity in heat-stressed broilers

1. Glutathione peroxidase activity and serum malondialdehyde of heat-stressed broilers were increased in the early period of heat exposure, and then these parameters decreased.

2. The lesion scores of bursa of Fabricius in heat-stressed broilers were increased and decreased in accordance with the activity of glutathione peroxidase and serum malondialdehyde.

3. High environmental temperature had not affected relative bursa of Fabricius weight and NDV-HI titer of heat-stressed broilers.

4. We concluded that heat-stressed broilers could adapt to oxidative stress, and environmental temperature set at 38±2 °C had not affected humoral immunity.

Effect of gestational and postnatal environmental temperature on metabolic rate in the altricial rodent, Phyllotis darwini

1. In the altricial rodent, Phyllotis darwini, we found higher body temperatures and faster developmental rates of the thermoregulatory capacity in neonates born from cold- than warm-acclimated mothers.

2. This difference could be explained by maternal effects on the litter, such as high levels of catecholamines and thyroxin levels, high concentration of the uncoupled protein and larger quantity of brown adipose tissue as a consequence of cold acclimation.

3. The exposition of mothers and the maintenance of cold condition during the early development might be responsible of the high metabolism and better thermoregulatory capacity of newborns.

Cooled neutrophils become deposited in the microcirculation after infusion: A potential mechanism for microvascular disruption following tissue hypothermia

1. We examined whether changes in rigidity and adhesiveness of neutrophils exposed to cooling and rewarming observed in vitro might impair microvascular perfusion in vivo. Neutrophils from donor rats were fluorescently (calcein-AM) or radioactively (Indium-111) labelled, incubated at 10 or 37 °C in vitro, and infused into recipients. Changes in transit rate and adhesive behaviour within post-capillary venules was quantified in m. extensor digitorum longus (EDL) using intravital microscopy, and tissue distribution determined.

2. There was an increased propensity of cooled cells to undergo adhesion following transfer into the recipient rat. However, cooling had no effect on median transit (354 μm s⁻¹) or rolling (14 μm s⁻¹) velocities during the first 5 min after infusion suggesting that cooling promotes adhesion, but does not delay passage through capillaries. Cooled neutrophils subsequently transformed to stationary adhesion. Their immobilisation was higher than for cells held at 37 °C (P<0.05), and once immobilised they remained firmly adherent to the vessel wall. Cooled, radiolabelled neutrophils showed tissue-specific accumulation after 3 min, but were cleared to the same extent as warmed cells by 20 min.

3. Our data suggest that cooling and rewarming of neutrophils impairs their ability to transit microvessels, reflecting changes in adhesive and mechanical properties observed in vitro, and may contribute to cold-associated circulatory pathology.

Acute effect of a single whole-body cryostimulation on prooxidant–antioxidant balance in blood of healthy, young men

1. We have examined the prooxidative–antioxidative reaction to extremely low temperatures (−130 °C) during a one-time cryostimulation in 15 young, clinically healthy individuals.

2. The total lipid peroxides as the total oxidative status (TOS) and the total antioxidative status (TAS) were measured in blood plasma collected in the morning of the day of cryostimulation, 30 min after the cryostimulation, and on the following morning.

3. The level of stress expressed by total oxidative status in plasma, resulting from exposure to extremely low temperatures, was statistically significantly lowered 30 min after leaving the cryochamber than prior to the exposure. The next day, the TOS level still remained lower than the initial values. The TAS level decreased after leaving the cryochamber and remained elevated the following day.

Antioxidative defense organization in retroperitoneal white adipose tissue during acclimation to cold—The involvement of l-arginine/NO pathway

1. Retroperitoneal white adipose tissue (RpWAT) antioxidative defense was investigated in untreated, l-arginine-treated and N^ω-nitro-l-arginine methyl ester (l-NAME)-treated rats kept at 4±1 °C (1, 3, 7, 12, 21 and 45 days) and compared to control rats at 22±1 °C.

2. Cold-acclimation-induced RpWAT weight decrease was accompanied by a decline in glutathione level and increased activity of manganese superoxide dismutase (MnSOD), glutathione S-transferase (GST), catalase, glutathione peroxidase and glutathione reductase at different time-points.

3. l-arginine accelerated RpWAT weight decrease, the increase in MnSOD and GST activities and the prolonged increase of catalase, MnSOD and GST activities. l-NAME delayed cold-induced catalase activity increase and tissue weight decrease. Prolonged l-NAME-treatment had a similar effect on RpWAT as l-arginine.

4. Results suggest the involvement of l-arginine/NO pathway in RpWAT oxidative metabolic augmentation induced by cold-acclimation.

Metabolic rate, maximum metabolism, and advantages of torpor in the fat mouse Steatomys pratensis natalensis Roberts, 1921 (Dendeomurinae)

1. The fat mouse Steatomys pratensis natalensis (mean body mass 37.4±0.43 (se)) has a low euthermic body temperature T_b=30.1–33.8 °C and a low basal metabolic rate (BMR)=0.50 ml O₂ g⁻¹ h⁻¹.

2. Below an ambient temperature (T_a)=15 °C, the mice were hypothermic.

3. The lowest survivable T_a=10 °C.

4. Torpor is efficient in conserving energy between T_a=15–30 °C, below T_a=15 °C, the mice arouse.

5. Euthermic and torpid mice were hyperthermic at T_a=35 °C.

6. Thermal conductance was 0.159 ml O₂ g⁻¹ h⁻¹ °C⁻¹, 98.8% of the expected value.

7. Non-shivering thermogenesis (NST) was 2.196 ml O² g⁻¹ h⁻¹ (3.69×BMR).

8. Maximal oxygen consumption, however, was 3.83 ml O₂ g⁻¹ h⁻¹ (6.44×BMR), indicating that other methods of heat production are additive.

9. Because fat mice conserve energy by torpor only between T_a=15–30 °C, we suggest that torpor may be a more important mechanism for surviving food shortages than for surviving cold weather.

The effects of melanocortin agonists and antagonists on leptin-induced fever in rats

1. Over three experiments, separate groups of adult male Sprague–Dawley rats received intracerebroventricular (ICV) injections of either vehicle, recombinant rat leptin (1 μg), or leptin (4 μg), then two ICV injections, 30 min apart of vehicle/vehicle, leptin (4 μg)/vehicle, vehicle/α-MSH (300 ng), or leptin/α-MSH, and then vehicle/vehicle, leptin (4 μg)/vehicle, vehicle/ SHU-9119 (200 ng; a MC 3/4 receptor antagonist), or leptin/SHU-9119. Core temperatures (T_c), food intake and body weights were monitored.

2. Four microgram leptin resulted in the induction of fever, an effect blocked by injection of α-MSH. Antagonism of MC 3/4 receptors with SHU-9119 did not augment leptin-induced fever, but did block the inhibitory actions of leptin on food intake.

3. These data demonstrate the inhibitory effects of exogenous α-MSH on leptin-induced fever, but suggest that endogenous melanocortin action at MC 3/4 receptors does not tonically inhibit febrigenesis caused by leptin administration.

Yield-SAFE: A parameter-sparse, process-based dynamic model for predicting resource capture, growth, and production in agroforestry systems

1. Silvoarable agroforestry (SAF) is the cultivation of trees and arable crops on the same parcel of land. SAF may contribute to modern diversified land use objectives in Europe, such as enhanced biodiversity and productivity, reduced leaching of nitrogen, protection against flooding and erosion, and attractiveness of the landscape. Long-term yield predictions are needed to assess long-term economic profitability of SAF.

2. A model for growth, resource sharing and productivity in agroforestry systems was developed to act as a tool in forecasts of yield, economic optimization of farming enterprises and exploration of policy options for land use in Europe. The model is called Yield-SAFE; from “YIeld Estimator for Long term Design of Silvoarable AgroForestry in Europe”. The model was developed with as few equations and parameters as possible to allow model parameterization under constrained availability of data from long-term experiments.

3. The model consists of seven state equations expressing the temporal dynamics of: (1) tree biomass; (2) tree leaf area; (3) number of shoots per tree; (4) crop biomass; (5) crop leaf area index; (6) heat sum; and (7) soil water content. The main outputs of the model are the growth dynamics and final yields of trees and crops. Daily inputs are temperature, radiation and precipitation. Planting densities, initial biomasses of tree and crop species, and soil parameters must be specified.

4. A parameterization of Yield-SAFE is generated, using published yield tables for tree growth and output from the comprehensive crop simulation model STICS. Analysis of tree and crop growth data from two poplar agroforestry stands in the United Kingdom demonstrates the validity of the modelling concept and calibration philosophy of Yield-SAFE. A sensitivity analysis is presented to elucidate which biological parameters most influence short and long-term productivity and land equivalent ratio.

5. The conceptual model, elaborated in Yield-SAFE, in combination with the outlined procedure for model calibration, offers a valid tool for exploratory land use studies.

Localization and some properties of lysosomal dipeptidases in rat liver

1. 1. The rates of hydrolysis of 26 synthetic depeptides by extracts from highly purified lysosomal fractions from rat liver at pH 5.0 and by whole liver homogenates at pH 7.4 have been determined. Extracts from the lysosomal fractions hydrolysed most peptides at a lower rate per mg protein than the homogenates, and some peptides not at all.

2. 2. Properties of two dipeptidases present in the extracts from the lysosomal fractions, splitting Ile-Glu and Leu-Gly, respectively, were studied in greater detail. The enzyme that hydrolysed Ile-Glu was strongly activated by dithiothreitol, showed optimal activity at pH 4.5 and had a molecular weight of about 120 000. Leu-Gly dipeptidase did apparently not contain an essential thiol group and had a molecular weight of approx. 90 000. It showed maximal activity at pH 6.5.

3. 3. After differential centrifugation of liver homogenates, Ile-Glu and Leu-Gly-splitting activities were determined in the fractions, under the optimal conditions mentioned above. The Ile-Glu-hydrolysing enzyme activity showed about the same distribution as the lysosomal marker enzyme acid phosphatase. Leu-Gly-splitting activity, however, was largely present in the cytosol fraction, with only a small peak in the lysosomal fraction. We obtained evidence that the activities present in the lysosomal fraction and in the cytosol fraction were due to different enzymes, and that one of these enzymes was localized exclusively in lysosomes.

4. 4. It is concluded that some dipeptides originating from intralysosomal proteolysis might be split by lysosomal dipeptidases, whereas others are probably hydrolysed only in the extra-lysosomal compartment of the cell.

Mathematical modelling of ATP, K and Na interactions with (Na + K)-ATPase occurring under equilibrium conditions

The controlling effect of ATP, K⁺ and Na⁺ on the rate of (Na⁺ + K⁺)-ATPase inactivation by 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) is used for the mathematical modelling of the interaction of the effectors with the enzyme under equilibrium conditions.

1. 1. Of a series of conceivable interaction models, designed without conceptual restrictions to describe the effector control of inactivation kinetics, only one fits the experimental data described in a preceding paper.

2. 2. The model is characterized by the coexistence of two binding sites for ATP and the coexistence of two separate binding sites for K⁺ and Na⁺ on the enzyme-ATP complex. On the basis of this model, the effector parameters fitting the experimental data most closely are estimated by means of nonlinear least-squares fits.

3. 3. The apparent dissociation constants for ATP of the enzyme-ATP complex or of the enzyme-(ATP)₂ complex are computed to lie near 0.0024 mM and 0.34 mM, respectively, irrespective of whether K⁺ and Na⁺ were absent or K⁺ and K⁺ plus Na⁺, respectively, were present in the experiments.

4. 4. The origin of the high and the low affinity site for binding of ATP to the (Na⁺ + K⁺)-ATPase molecule is traced back to the coexistence of two catalytic centres which, although primarily equivalent as to the reactivity of their thiol groups with NBD-Cl, are induced into anticooperative communication by ATP binding and thus show an induced geometric asymmetry.

The effect of hormones on synthesis of the region linking chondroitin sulfate to protein

1. 1. Particulate fractions of costal cartilage from young rats are capable of catalyzing the formation of the first two monosaccharide units of the chondroitin sulfate-protein linkage region.

2. 2. Hormonal imbalance has been shown to influence the activity of the glycosyltransferases responsible for the sequential transfer of xylose and galactose from UDPxylose and UDPgalactose, respectively, in the formation of the linkage region.

3. 3. The activity of xylosyltransferase was found to be decreased in costal cartilage of diabetic, thyroidectomized and hypophysectomized rats, but not in rats injected with either testosterone or hydrocortisone. In the latter two treatment groups, galactosyltransferase activity was decreased only in the group receiving hydrocorsitone.

4. 4. The combined results of this and previous studies suggest that decreased levels of chondroitin sulfate in diabetic, thyroidectomized and hypophysectomized animals are due to interference in the synthesis of the linkage region of the proteoglycan at the xylosyltransferase level whereas hydrocortisone acts primarily at the level of the galactosyltransferase.

Effects of anesthetic alcohols on membrane transport processes in human erythrocytes

1. 1. Anesthetic alcohols (pentanol, hexanol and heptanol) were found to increase the fluidity of red cell membrane lipids as monitored by the fluorescence depolarization of diphenylhexatriene. The relative potency of the alcohols was found to be parallel to their relative membrane/water partition coefficients.

2. 2. Hexanol had biphasic effect on erythritol uptake by simple diffusion by red cells. At concentrations less than 9 mM, hexanol had no significant effect. At concentrations greater than 9 mM, there was an approximately linear increase in erythritol permeability with increasing alcohol concentration.

3. 3. The facilitated transport of uridine was markedly inhibited by hexanol. Hexanol at 6 mM produced a 65% inhibition of uridine (4 mM) uptake. Hexanol decreased both the apparent K_m and V values for the equilibrium exchange of uridine.

4. 4. The facilitated transport of galactose was only slightly inhibited by hexanol.

5. 5. Hexanol was without effect on the passive and active fluxes of Na⁺ and K⁺ in red cells with altered cation contents. Cells that were slightly depleted of K⁺ and cells that were highly K⁺-depleted were both insensitive to hexanol.

Fluorimetric determination of the resting potential changes associated with the chemotactic response in Paramecium

1. (1) Evidence is presented which indicates that the carbocyanine dye (3,3′ dipropyl thiadicarbocyanine) can be used as a spectroscopic probe for monitoring the resting potential across the plasma membrane of the ciliated protozoan Paramecium.

2. (2) The dye at low concentrations ( 1 μM) does not affect either the viability or the motility of the cells, nor does it induce a chemotactic response.

3. (3) The fluorescence of the dye bound to the cells alters as the potential across the membrane is changed by increasing the external cation concentration.

4. (4) The absorbance of the bound dye also changes in response to an alteration of the membrane potential.

5. (5) The membrane potential changes as measured by the fluorescence method have been correlated with the measurements of the potential estimated by microelectrode methods.

6. (6) Both cations which induce a negative chemotactic response in Paramecium (K⁺, Na⁺, Ba²⁺) and several non-toxic cations bring about a rapid depolarization of the plasma membrane. The significance of these rapid changes in relation to the swimming behaviour of the ciliate is discussed.

The genetic basis of altitudinal variation in the wood frog Rana sylvatica II. An experimental analysis of larval development

Summary The variation in larval developmental patterns in the wood frog, Rana sylvatica, along an elevation gradient of 1,000 m was experimentally studied. Larval populations at high elevation ponds had lower growth rates, developmental rates and were larger at all stages (including metamorphic climax) than larval populations developing in low elevation ponds. There was considerable variation among ponds within each elevation in both the length of the larval period and size at metamorphic climax. Reciprocal transplant experiments and controlled laboratory experiments revealed that most of the observed variation between high and low elevation populations could be explained by the effects of temperature induction during ontogeny. Significant genetic differences in growth rates and non-genetic maternal effects on developmental rates between larvae of mountain origin and lowland origin were also demonstrated. Selection in both environments has acted to minimize the prevailing environmental effect of pond temperature on developmental rates, but has accentuated the prevailing environmental effects on larval body size. As a consequence mountain larvae were capable of completing metamorphosis sooner and at a larger size in all environments than lowland larvae.