On the nature of the maximum gelation temperature in polymer gels

A theoretical framework is provided to explain the maximum gelation temperature in thermoreversible gelatin gels. Arrenhius plots of the inverse of the induction time of gelation versus the reciprocal of the setting temperature were linear for the different initial sol concentrations studied. Moreover, when extrapolated to higher temperatures, these lines intersected at a critical temperature. In this work, we show how this critical temperature corresponds to the temperature at which the polymer sol is in equilibrium with its activated state for a gelation reaction. We define this critical temperature as the maximum gelation temperature.     

重组细胞因子制品热原质试验中的降温现象

中国生物制品规程规定采用家兔试验法进行热原试验。规程要求当家兔降温≥０６℃或２只及２只以上降温在０４～０６℃时应重试。在４２０批各类细胞因子热原质试验中发现２３批出现降温,重试后合格率为１００％。降温原因分析表明降温现象与热原性物质无关,与制品种类不存在显著相关性。因此,热原试验中出现家兔降温时是否需要重试值得商榷     

Selecting temperature for protein crystallization screens using the temperature dependence of the second virial coefficient

Protein crystals usually grow at a preferable temperature which is however not known for a new protein. This paper reports a new approach for determination of favorable crystallization temperature, which can be adopted to facilitate the crystallization screening process. By taking advantage of the correlation between the temperature dependence of the second virial coefficient (B(22)) and the solubility of protein, we measured the temperature dependence of B(22) to predict the temperature dependence of the solubility. Using information about solubility versus temperature, a preferred crystallization temperature can be proposed. If B(22) is a positive function of the temperature, a lower crystallization temperature is recommended; if B(22) shows opposite behavior with respect to the temperature, a higher crystallization temperature is preferred. Otherwise, any temperature in the tested range can be used.     

The nature of the dependence of the rate of development on temperature determines the greatest efficiency of metabolism at optimal temperatures

Metabolism intensity and development rate have different pattern of dependence on temperature. Oxygen intake and several other metabolic processes bear an exponential relationship to temperature. The pattern of this relationship is similar in different poikilothermal species. On the contrary, the relationship between the rate of development and temperature is species-specific and more complex. Hence, the curves obtained by plotting oxygen intake per developmental stage against temperature resemble parabola and the minimum values of oxygen intake correspond to optimal temperatures. Such a correspondence is almost solely determined by parameters of the relationship between the rate of development and temperature. Therefore, the efficiency of metabolism does not determine the range of optimal temperatures. It is suggested that adaptive alterations of this range during evolution proceed via changes of the parameters of relationship between the rate of development and temperature dependence. Relatively small number of mutations is required to produce such changes.     

Temperature compensation in the nervous system of the grasshopper

Abstract The wind-sensitive head hair neurones of the grasshopper Schistocerca americana (Drury) are influenced by temperature, increasing the number of spikes fired in response to a given hair deflection as temperature increases. Because these neurones show similar increases in spike output for greater hair deflections, an interneurone which receives their input would not be able to distinguish changes in stimulus strength from changes in temperature, unless the effects of temperature were compensated or independently measured. This study examines the effects of temperature on the output of the tritocerebral commissure giant (TCG), an interneurone that receives wind hair input. Some wind hairs provide excitatory input to the TCG, while others are inhibitory (Bacon & Möhl, 1983). Temperature variations similar to those measured in freely moving animals were applied to the wind hairs and TCG while the interneurone's spike output was recorded. Two manipulations resulted in temperature compensated outputs from the TCG: (1) When both excitatory and inhibitory hair fields were stimulated simultaneously, the temperature sensitivity of the interneurone's spike output was significantly lower than when the excitatory hairs alone were stimulated. (2) The spike output of the TCG showed very little sensitivity to temperature changes which occurred only at its wind hair inputs, the temperature of the interneurone itself remaining constant. It is therefore possible for the output of a neural circuit to be temperature compensated even though the circuit itself may be composed of temperature-sensitive units. Possible mechanisms by which temperature compensation may be produced in the TCG are discussed, and the behavioural relevance of the conditions under which TCG output is temperature compensated is considered.     

The role of central and peripheral temperature changes in the regulation of thermal polypnea in the chicken

The temperature of free-flowing blood in the aorta, the skin temperature of the comb, and the temperature of the skin under the feathers, of nine male chickens were measured, before, during and after exposure to a hot environment (45°C). Respiratory frequencies were also recorded, and no evidence was obtained that thermal polypnea occured before the deep-body temperature increased. In some birds, the highest respiratory frequency was noted after the air temperature was lowered. It is suggested that, although an increase in skin temperature is not involved in the initiation of thermal polypnea, changes in skin temperature may modify the respiratory pattern once thermal polypnea is established.     

Role of the temperature factor in determining the nature of the chronotropic response of the heart of cats in the simulation of increased venous inflow

The heart rate changes in response to the imitation of venous input to the heart by infusion of an additional blood volume to the right atria have been studied on anesthetized by chloralose cats. It has been discovered that patterns of the heart rate changes are determined by the infused blood temperature if it is equal to the blood temperature in heart, tachycardia appears, if it is below this temperature, bradycardia develops. These data explain, from our point of view, the contradictory results obtaining by different authors in experiments with the imitation of the increased venous input (Bainbridge reflex).     

Kinetic modelling of the degradation of the alpha-tocopherol in biodiesel-rape methyl ester

The aim of this work was to study the influence of three major factors (light, atmospheric oxygen, temperature) responsible for the degradation of tocopherols. The evolution of alpha-tocopherol contents was analysed by high-performance liquid chromatography. Taguchi's experimental design was applied to establish a mathematical model of alpha-tocopherols degradation in function of the studied parameters especially in a domain of temperature between 50 degrees C and 150 degrees C. The results show that the major factor is the temperature, especially above 100 degrees C. Light is a negligible factor, meaning that degradation is mainly due to an autoxidation phenomenon. Moreover, only interactions between temperature and atmospheric oxygen have been observed especially above 100 degrees C. The mathematical model was validated for a temperature of 75 degrees C and permits to calculate a predictive speed of degradation in this domain.     

四种类型杀虫剂对麦长管蚜的温度效应及其与主要解毒酶的关系

为了明确杀虫剂毒力受温度的影响及其程度,本文测定了4大类8种药剂在10～25℃下对麦长管蚜的毒力;并测定了麦长管蚜Sitobion avenae(Fabricius)在不同温度下2个解毒酶和1个靶标酶的活性差异。结果表明,高效氯氰菊酯对麦长管蚜表现不规则负温度系数,啶虫脒表现不规则正温度系数,高效氟氯氰菊酯对麦长管蚜的毒力不受温度影响,其他药剂(辛硫磷、毒死蜱、灭多威、丁硫克百威、吡虫啉)均表现为明显的正温度系数效应,以有机磷类杀虫剂表现最为明显,毒死蜱温度系数高达57.70。酶活性实验表明:麦长管蚜在高温下GST活性增强,羧酸酯酶和乙酰胆碱酯酶活性降低。它们的变化规律表明:GST活性与负温度系数密切相关,正温度系数与羧酸酯酶活性和靶标酶乙酰胆碱酯酶活性有关。     

Stimulation of the salt receptor of the blowfly. II. Temperature

The response of the salt receptor of the blowfly increased with increasing ambient temperature. At constant ambient temperature, the response increased as the relative humidity was raised. At low relative humidity, the temperature of the stimulating solution near its air interface was markedly below ambient temperature, due to evaporation. Warming and cooling the tip of the sensillum while recording from its side respectively raised and lowered the frequency of "spontaneous" action potentials of the receptor. The results indicate that the response of the salt receptor is dependent on the temperature of the stimulus. The Q10 is probably several times greater than one.     

Electrophysiological identification of cold receptors on the antennae of the ground beetle Pterostichus aethiops

Abstract.  In single-sensillum extracellular electrophysiological recordings, terminal campaniform sensilla at the tip of antennae of the ground beetle Pterostichus aethiops (Pz., 1797) show action potentials of three sensory cells, A-, B- and C-cells, distinguished by differences in their spike amplitudes. Only the A-cell, with the largest spike amplitude, is highly sensitive to temperature fluctuations, showing remarkable changes in its firing rate induced by changes in temperature of 0.1 °C. The firing rate of A-cells at 23 °C varies from 15–52 Hz among different beetles. Mean impulse frequency of A-cells is found to be a function of steady temperature, the firing rate decreasing with temperature increase. A-cells respond to a rapid temperature drop with a strong phasic-tonic reaction; larger decreases in temperature evoke higher peak frequency values. Maximum peak frequencies, varying from 380–630 Hz in different beetles, are induced by temperature decreases of 3–10 °C, whereas temperature rise strongly inhibits impulse activity of the A-cell. The first manifestation of rapid warming in the nerve impulse sequence is a very long interspike period, followed by diminished activity. Both the length of the long interspike period and the rate of following impulse activity are functions of temperature change; hence, A-cells respond to temperature changes as typical cold receptors, similar to coeloconic and short hair-like sensilla in other insects.     

Predicting the growth of the amphibian chytrid fungus in varying temperature environments

Environmental temperature is a crucial abiotic factor that influences the success of ectothermic organisms, including hosts and pathogens in disease systems. One example is the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), which has led to widespread amphibian population declines. Understanding its thermal ecology is essential to effectively predict outbreaks. Studies that examine the impact of temperature on hosts and pathogens often do so in controlled constant temperatures. Although varying temperature experiments are becoming increasingly common, it is unrealistic to test every temperature scenario. Thus, reliable methods that use constant temperature data to predict performance in varying temperatures are needed. In this study, we tested whether we could accurately predict Bd growth in three varying temperature regimes, using a Bayesian hierarchical model fit with constant temperature Bd growth data. We fit the Bayesian hierarchical model five times, each time changing the thermal performance curve (TPC) used to constrain the logistic growth rate to determine how TPCs influence the predictions. We then validated the model predictions using Bd growth data collected from the three tested varying temperature regimes. Although all TPCs overpredicted Bd growth in the varying temperature regimes, some functional forms performed better than others. Varying temperature impacts on disease systems are still not well understood and improving our understanding and methodologies to predict these effects could provide insights into disease systems and help conservation efforts.     

Quantifying the instability of core temperature in rodents

Radiotelemetry provides researchers with the ability to sample the core temperature of rodents and other species rapidly. Compared to large mammals, the time-course of core temperature of rodents is variable and their data are often averaged into bins of one or more hours for publication. When viewing averaged data, a stable core temperature over a wide range of ambient temperatures is observed; however, if the time-course of core temperature of individual animals is examined closely with a sampling period of 1–10 min, a continuous waxing and waning of temperature is observed. It is proposed that calculating the change in temperature from one time point to the next (i.e., temperature differential) is an informative measure of the performance of the thermoregulatory system. A quantitative measure of the stability of the thermoregulatory system can be determined by calculating the absolute value of the temperature differential. It is shown that the absolute temperature differential (ATD) is dependent on ambient temperature, genetic strain, type of cage bedding, and body size. The ATD is simple to calculate from telemetry data and may be an important parameter for the study of rodent thermal physiology.     

Modelling the effect of temperature variation on the seasonal dynamics of Ixodes ricinus tick populations

Seasonal variation in temperature is known to drive annual patterns of tick activity and can influence the dynamics of tick-borne diseases. An age-structured model of the dynamics of Ixodes ricinus populations was developed to explore how changes in average temperature and different levels of temperature variability affect seasonal patterns of tick activity and the transmission of tick-borne diseases. The model produced seasonal patterns of tick emergence that are consistent with those observed throughout Great Britain. Varying average temperature across a continuous spectrum produced a systematic pattern in the times of peak emergence of questing ticks which depends on cumulative temperature over the year. Examination of the effects of between-year stochastic temperature variation on this pattern indicated that peak emergence times are more strongly affected by temperature stochasticity at certain levels of average temperature. Finally the model was extended to give a simple representation of the dynamics of a tick-borne disease. A threshold level of annual cumulative temperature was identified at which disease persistence is sensitive to stochastic temperature variation. In conclusion, the effect of changing patterns of temperature variation on the dynamics of I. ricinus ticks and the diseases they transmit may depend on the cumulative temperature over the year and will therefore vary across different locations. The results also indicate that diapause mechanisms have an important influence on seasonal patterns of tick activity and require further study.     

Regulation of thermogenesis in flowering Araceae: the role of the alternative oxidase

The inflorescences of several members of the Arum lily family warm up during flowering and are able to maintain their temperature at a constant level, relatively independent of the ambient temperature. The heat is generated via a mitochondrial respiratory pathway that is distinct from the cytochrome chain and involves a cyanide-resistant alternative oxidase (AOX). In this paper we have used flux control analysis to investigate the influence of temperature on the rate of respiration through both cytochrome and alternative oxidases in mitochondria isolated from the appendices of intact thermogenic Arum maculatum inflorescences. Results are presented which indicate that at low temperatures, the dehydrogenases are almost in full control of respiration but as the temperature increases flux control shifts to the AOX. On the basis of these results a simple model of thermoregulation is presented that is applicable to all species of thermogenic plants. The model takes into account the temperature characteristics of the separate components of the plant mitochondrial respiratory chain and the control of each process. We propose that 1) in all aroid flowers AOX assumes almost complete control over respiration, 2) the temperature profile of AOX explains the reversed relationship between ambient temperature and respiration in thermoregulating Arum flowers, 3) the thermoregulation process is the same in all species and 4) variations in inflorescence temperatures can easily be explained by variations in AOX protein concentrations.     

Average normal temperature of the chicken in the morning and after 1-2 days of fasting

On the morning the average temperature of the growing chicken. It is found at 41.8 degrees C +/- 0.18 degrees. After one day without having eaten, the bodily temperature diminishes to 40.41 degrees +/- 0.97 degrees (-1.39 degrees). After two days without having eaten the temperature diminishes to 39.68 degrees C +/- 0.89 degrees (-2.12 degrees). After the first day of re-feeding the average temperature is 41.28 degrees C +/- 0.52 degrees C. During the period of no feeding the reduction in bodily temperature depends on the metabolic material availability. We can assume that the thermoregulator mechanisms are not modified by non-feeding and that the reduction in temperature is caused by the non efficiency of their normal efferents.     

Ligand-modulation of the stability of the glucose transporter GLUT 1

The glucose transporter GLUT 1 was isolated from human erythrocytes and reconstituted into endogenous membrane lipids. Results from thermal denaturation studies, using differential scanning calorimetry, indicate that the thermal denaturation temperature of GLUT 1 is significantly lower in the presence of ATP. The lowering of this transition temperature is very dependent on pH. At more acidic pH, ATP has a greater effect of lowering the thermal denaturation temperature of the protein. For example, with 4.8 mM ATP, the denaturation endotherm is lowered by over 10 degrees at pH 4.3, whereas at pH 7.4, ATP does not alter this transition temperature. However, a change in pH alone, in the absence of ATP, has very little effect on the denaturation temperature. Both glucose and salt partially reverse the lowering of the temperature of thermal denaturation caused by ATP. Studies of acrylamide quenching of the Trp residues of GLUT 1 indicate that at neutral pH, ATP increases the Stern-Volmer quenching constant, while glucose lowers it. The results indicate that ATP binds to GLUT 1 and destabilizes the native structure, leading to a lowering of the thermal denaturation temperature and an increase in acrylamide quenching. The effects of ATP are reversed in part by glucose and are also partly electrostatic in nature.     

Influence of growth temperature on the acid phosphatase activity in the yeast Yarrowia lipolytica

Abstract The adaptation of the yeast Yarrowia lipolytica 76-18 to growth temperature was studied by measuring the levels of secreted and intracellular acid phosphatase activities during growth at five temperatures from 8 to 36 °C. The intracellular acid phosphatase activity is maximal at a growth temperature of 20 °C. The level of the secreted phosphatase activity decreases as growth temperature increases from 15 to 36 °C. It is the growth temperature itself and not the growth rate that regulates these activities. The observed dependence of the acid phosphatase activity on the growth temperature indicates a possible participation of acid phosphatases in the temperature adaptation of yeast cells.     

Thermodynamics of the water permeability of plant cuticles: characterization of the polar pathway

The water permeability of cuticles isolated from the leaves of 14 plant species was measured at temperatures from 10 degrees C to 55 degrees C at 5 K intervals. Permeances increased slightly with temperatures < or =35 degrees C and drastically in the higher temperature range. The data were analysed according to the Arrhenius formalism which led to distinct plots for the lower and higher temperature range, respectively. Activation energies of permeation for the lower temperature range were estimated to amount to 15.2-52.5 kJ mol(-1), at higher temperature activation energies ranged from 52.2-117.3 kJ mol(-1). This thermodynamics approach is used for further elucidating the pathway taken by water across the plant cuticle. Based on the results of this study it is hypothesized that the diffusion of water occurs along polysaccharide strands crossing the cuticle and that the transport properties of these polar pathways change with temperature.