Characterization of DNA degradation using direct current conductivity and dynamic dielectric relaxation techniques

The purpose of this study was to evaluate DNA degradation upon thermal heating using dielectric relaxation and direct current (DC) conductivity methods. Herring sperm DNA, human growth hormone (HgH) plasmid DNA, and secreted alkaline phosphatase (SEAP) plasmid DNA were used as the examples. DNA was heated at 80°C for 1 hour. The dielectric relaxation spectra as a function of the applied field frequency were measured for HgH DNA at 0.5 hours and at 1 hour. The frequency range covered was from 10 kHz to 100 kHz. The DC conductivity measurements were made for all 3 kinds of DNA at 4 time points: 0 hours, 0.5 hours, 0.75 hours, and 1 hour. At each time point the DC conductivity was measured for each sample as a function of concentration via water dilution. The results show that the dielectric relaxation method is less sensitive in characterizing heat-driven DNA degradation. Conversely, DC conductivity is very sensitive. The semiquantitative dependence of the conductivity upon heating suggests that DNA degradation involves more than plasmid DNA nicking. Double strand and single strand breaks may also occur. In addition, herring sperm DNA, HgH DNA, and SEAP DNA, though similar in their DC conductivity functional forms upon dilution, exhibit significant differences in their responses to sustained heating.     

The heat transfer analysis of nanoparticle heat source in alanine tissue by molecular dynamics

The purpose of this study is to simulate the heat transfer problem when the 3-D Alanine tissue is heated by the gold nanoparticle in the field of molecular dynamics. In this paper, the Alanine molecule is adopted and its parameters are available in the GROMACS protein data bank. A computing algorithm is developed to evaluate the heat transfer phenomena in the nano-scale biological system based on the molecular dynamics and the protein data bank. The value of the thermal conductivity of Alanine is calculated from the autocorrelation function of the Green-Kubo formalism and this result has a roughly approximation with the bulk thermal conductivity reported by experimental data . Two kinds of problems are investigated in the paper. One is the Alanine tissue heated by the constant heat source and the other is by the time-varying heat source. The numerical results show that a temperature jump exists around the source and the temperature profiles drop to the environmental temperature within a very short distance. It concludes that only a small region around the nano-scale heat source is affected by the heated process. Therefore, the results of the nanoparticle-heated method could be applied to the clinical therapy of tumor, and the normal cells are destroyed only within a smaller region than those of chemotherapy or surgery.     

Effects of the discharge of thermal effluent from a power station on Lake Wabamun,Alberta, Canada — Limnological features

The physical and chemical aspects of Lake Wabamum have been described. Modifications to the thermal and dissolved oxygen regimes through the discharge of thermal effluent into the eastern region of the lake are discussed. This discharge has, therefore, changed the environmental conditions under which the biota exists in the eastern portion of the lake. It was also shown that this discharge of heated water had no effect upon the water chemistry while the power station itself contributed silica, in the form of fly ash, to the system. Tables of the phytoplankton, zooplankton, aquatic macrophytes, and fish are provided. From a biological and limnological stand point the lake can be classified as a moderately eutrophic lake, especially in the eastern portion.     

Physical explanations and biological explanations,empirical laws and a priori laws

Philosophers intent upon characterizing the difference between physics and biology often seize upon the purported fact that physical explanations conform more closely to the covering law model than biological explanations. Central to this purported difference is the role of laws of nature in the explanations of these two sciences. However, I argue that, although certain important differences between physics and biology can be highlighted by differences between physical and biological explanations, these differences are not differences in the degree to which those explanations conform to the covering law model, which fits biology about as well as it does physics.     

A soil heat and water transfer model to predict belowground grass rhizome bud death in a grass fire

Question: Grasses often resprout from surviving belowground buds following a fire in which aboveground matter is consumed. We used a soil heat and water transport model to present a general method for determining the potential mortality of rhizome buds due to fire for three tallgrass species (Andropogon gerardii, Sorghastrum nutans, and Panicum virgatum). Methods: Soil heating was described by physical processes that include heat conduction through the soil and heating and evaporation of soil water. We considered the following factors: soil moisture, texture, mineral thermal conductivity, maximum surface temperature, and fire residence time. Simulated soil temperature profiles were combined with measured belowground bud distributions to determine the proportion of buds expected to be heated to lethal temperatures under various conditions. Location: Wisconsin, USA. Results: Lethal temperatures for buds do not occur below ～2 cm, and at least 30% of rhizome buds remain below lethal temperatures, even under extreme conditions. Conclusions: The model explains the possible mechanisms for grass belowground rhizome bud survival in fires. Changes in fire and soil conditions do not notably impact soil temperatures and rhizome bud survival.     

Head-body temperature differences in the Australian blue-tongued lizard, Tiliqua scincoides during radiant heating

When heated radiantly, head-body temperature gradients developed in both live and dead Tiliqua scincoides. The gradients were consistently larger in live than in dead individuals, indicating they were enhanced by a physiological component superimposed on the more basic physical components. Large gradients in the initial phases of heating represented a lag effect, the head core beginning to receive heat before the body core because it is closer to the heated surface. Once this lag effect subsided, the body heated more rapidly than the head because it presented a greater incident surface area per unit mass than did the head. Living lizards appeared to maintain head-body temperature differences until the maximum voluntary temperature was approached.     

作物水分供应订正函数的韦伯函数型

从作物水分生产潜力、潜在水分利用效率与水分满足率的关系及特点入手,引入水分供应订正函数的韦伯形式。与目前常见的水分供应订正函数形式相比,本文给出的韦伯形式的水分供应订正函数具有临界水分满足率和“旋回”特征,能较好地解释作物水分生产潜力与水分满足率之间的数量关系,模型的实用性较广。模型中位置参数表示临界水分满足率;尺度参数表示水分满足率的取值范围;形状参数决定水分供应订正函数的“峰度”和“偏斜度”。根据“图解法”可求取水分供应订正函数的相关参数。其参数也具有明确的生物学和物理学意义,参数值本身也较稳定,使模型在应用中可望具有良好的稳定性。     

Cell kill and tumor control after heat treatment with and without vascular occlusion in RIF-1 tumors

RIF-1 tumors (100-300 mg) were exposed in vivo to heat treatment (41-48 degrees C) for 30 min and then assayed for either cell survival or tumor control. The tumors were heated either with normal perfusion or with temporary vascular occlusion (clamped for 30 min prior to and during the 30-min treatment). The physical technique of water bath heating ensured temperature uniformity in both the perfused and vascularly occluded tumors. Survival curves for tumor cells heated under both conditions had a shoulder and exponential regions. While the T0's were not statistically different in the two cases, cells from the tumors whose blood flow had been occluded showed an enhanced sensitivity to heat as evidenced by a reduction of the shoulder by 2.5 degrees C. A similar increase in sensitivity was measured with the tumor cure assay with the TCT50 decreasing from 47 degrees C for unclamped tumors to 45 degrees C for clamped tumors. The two assays are therefore in excellent agreement in assessing the effectiveness of heat treatment and the influence of vascular occlusion on the heat sensitivity of this tumor. Since the clonogenic assay was performed immediately after treatment, this agreement between assays indicates that direct cell kill by heat is the major factor in determining cure in this tumor.     

The effect of media tonicity on Escherichia coli resistance to heating with different gradient

The influence of NaCl water solutions and glycerine hypertonic concentration on the survival of bacteria Escherichia coli B/r heated with different values of heat drop was investigated. It was shown that the transfer of cell suspensions from isotonic conditions to media with raised osmotic pressure, preliminarily heated up to 60 degrees C, and the following heating at this temperature inhibited differences in cell sensitivity to heating at different heat drop. Unlike, it was found that the transfer of cell suspensions from isotonic conditions to hypertonic media before and after heating at 60 degrees C increased differences in resistance of these microorganisms to heating at different heat drop. It is proposed that different resistance of bacteria to damaging action of hyperthermia at different heat drop, and a modified influence of hypertonic solutions on these differences may be due to heat induced destabilization of cell osmotic homeostasis. The extent of expression of this destabilization may be determined by a quantitative ratio of osmotic pressure values in the cell-suspension medium system in particular temperature and tonic environmental conditions.     

旧石器时代石制品热处理研究:回顾与展望

热处理技术作为旧石器时代古人类提高石器制作工艺水平的代表性技能, 一直以来倍受国际学术界的重视, 在已经开展的40余年工作中积累了丰硕的研究成果。由于我国旧石器时代石料的特点及热处理研究的某些技术手段本身存在局限性, 尚未在考古遗址中发现热处理行为及相关遗物, 目前我国热处理研究仍处于空白阶段。本文主要介绍旧石器时代热处理技术的原理与工艺及相关研究手段, 特别是针对热处理技术的实验研究。相信随着认识的加深, 石制品热处理研究会在我国旧石器考古学研究中发挥重要作用。     

Temporal and spatial distribution of the baetid Afroptilum sudafricanum in the sediment surface of a tropical stream

Shallowness and tropicality primarily relate to physical aspects of environmental regulation. These concern water input and output, with correlates associated with water level and salinity; energy balance and heat distribution, with correlates of temperature and density stratification; and largely wind-driven water movements, with consequences in chemical and biological distributions. Shallowness in a water-column affects the quantitative relationship between many stock quantities and flux rates per unit surface area. Evaporative loss of water is one familiar example; sensitivity to surface energy exchanges provides others. Somewhat different are processes that depend upon transmission with depth. Here light penetration, convective penetration and wind-generated turbulence with flow-depth relations are illustrative. Tropicality further influences by climatic factors, especially of solar radiation and rainfall. Energy balance tends to yield year-long elevated water temperature at all depths, but at a level dependent upon altitude. The magnitude and seasonal periodicity of water input is widely dependent upon the inter-tropical convergence zone in atmospheric circulation. Over the arid and semi-arid tropics, the lakes may lie in closed drainage basins and be influenced by evaporative concentration with salinization. Shallow lakes of tropical Africa are used to illustrate these varied environmental constraints and some of their biological consequences.     

Impact of microwave heating on the physico-chemical properties of a starch–water model system

The objective of this work was to understand the physico-chemical changes induced in a wheat starch model system as a result of microwave heating. Wheat starch dispersions in water, with final solids content of 33%, 40% or 50%, were heated in a microwave oven. Following heating the samples were stored at 25 °C for up to 120 h and analyzed periodically. Microwave heated gels were significantly different from conduction heated gels in all parameters measured. The differences in properties are a reflection of the differences in the heat and mass transfer of the different modes of heating. The lack of granule swelling and the resulting soft gel are two key observations. The results of this study suggest a different mechanism of starch gelatinization compared to conduction heating. The vibrational motion and the rapid increase in temperature also result in granule rupture and formation of film polymers coating the granule surface.     

热浪频次及间隔时间对闽楠和木荷苗木水力结构和非结构性碳水化合物的影响

近年来亚热带地区极端气候事件热浪发生频率增加,热浪频次及间隔时间的变化使热浪发生的模式及其对植物的胁迫方式更加多样化。高频热浪不仅通过热胁迫影响植物的碳固持速率,还会间接形成水分胁迫造成植物水力结构发生障碍,影响碳水化合物的运输。然而,目前亚热带树木水力结构和非结构性碳水化合物(NSC)对复杂热浪的模式的响应仍不明确。以亚热带主要阔叶树种闽楠(Phoebe bournei)和木荷(Schima superba)苗木为研究对象进行了热浪模拟试验,关注不同热浪频次(单次,两次)及重复热浪间隔时间(短间隔、中间隔、长间隔)对苗木茎部水力结构特征及NSC的影响,使用冲洗法测定水力结构中的导水率(K_h)、最大导水率(K_max)、比导率(K_s)、木质部栓塞百分数(PLC),使用蒽酮-硫酸比色法测定茎段非结构性碳水化合物含量。结果表明,(1)闽楠和木荷的水力结构和非结构性碳水化合物在树种间存在显著差异;(2)不同热浪频次对闽楠和木荷的K_max和PLC影响存在显著差异;(3)重复热浪间隔时间变长,木荷茎栓塞减轻,而闽楠茎栓塞增加,且植株栓塞越严重,茎NSC含量越少。总体上,闽楠的水力传输系统对热浪抗性较弱,在热浪后栓塞严重,导水率下降且无法完全恢复,且NSC含量与栓塞程度相关性较弱;而木荷水力传输系统抗性较强,在热浪后导水能力可能恢复至未受干扰水平,且其恢复程度与NSC含量紧密相关。该研究结果表明,高频热浪的发生会显著影响闽楠和木荷苗木茎部的导水能力,且不同间隔时间的重复热浪事件对植物水力结构的影响存在差异性,并且两个亚热带阔叶树种对热浪伴随的高温和水分胁迫的耐受性和耐受机制存在差异。     

Kinetics of electron transport, proton transfer and photophosphorylation in chloroplasts and their relation to temperature-induced structural changes in the thylakoid membrane

Effects of various temperatures on the rates of electron transport between two photosystems, the light-induced uptake of protons, kinetics of proton efflux from the chloroplasts in the dark and photophosphorylation were studied in isolated chloroplasts. There are correlations between the physical state of thylakoid membrane and the rates of electron- and proton transport processes. The temperature dependence of "structural" parameter (fluidity of lipids in membrane) as well as the rates of electron- and proton transport processes reveal the breaks under the same temperatures. Stimulation of photophosphorylation by temperature increasing correlates with the heat activation of chloroplasts latent ATPase due to thermoinduced structural changes in the heat activation of chloroplasts latent ATPase due to thermoinduced structural changes in the protein part of CF0-CF1 complex. The rate of photophosphorylation also correlates with the physical state of membrane lipids. Thermoinduced "melting" of the thylakoid membrane inhibits the ATP formation because of a decrease in photosystem 2 photochemical activity and stimulation of membrane conductivity for protons.     

Comparative Limnology of Several Reservoirs in Central India

Twenty four reservoirs in Central India were investigated for their physical, chemical and biological features. These reservoirs differed significantly in their size, physical features, chemical composition and vegetation. Three medium and major reservoirs recorded comparatively low electrical conductivity. All the eighteen minor reservoirs showed high conductivity and low transparency since they were all situated in densely populated urban areas polluted by human faeces and domestic sewage. The most abundant ions in water are calcium, carbonate and chloride. The phytoplankton was found to be dominated by Cyanophyceae. Rotifers dominated among zooplankton. All the minor reservoirs are highly eutrophicated. Among the major reservoirs Tawa Reservoir is oligotrophic while others are mesotrophic to eutrophic in nature.     

Environmental and hormonal influences upon EOD waveform in gymnotiform pulse fish.

Temperature is a major variable that affects all biological systems. Environmental temperature determines animal geographical distribution and activity, and influences their reproductive cycle, particularly within the temperate zone. Temperature, as a physical parameter, also strongly affects excitable tissues. The hypothesis of temperature as the most important environmental cue for the onset of breeding in gymnotiform pulse fish of the temperate zone is supported by: (a) a clear temporal correlation that was observed in the wild between water temperature and sexual maturity, and (b) the induction of gonadal maturation and sexual differences after acclimation at high temperature (28 degrees C) in the laboratory. Temperature sensitivity of EOD waveform (described in Brachyhypopomus pinnicaudatus and Gymnotus carapo) is characterized by the decrease of the EOD's late head-negative phase as temperature increases. This phenomenon depends on electrocyte properties since: (a) experimentally induced changes of discharge rate at constant temperature generate smaller EOD distortion, and (b) the effect of temperature upon EOD also depends on water conductivity. Temperature sensitivity of EOD waveform is negatively correlated with gonadal maturity in Brachyhypopomus pinnicaudatus. High temperature sensitivity was observed during the non-breeding season, whereas low temperature sensitivity was recorded during the breeding season. Temperature sensitivity of EOD waveform in both Brachyhypopomus pinnicaudatus and Gymnotus carapo was modulated by: (a) testosterone treatment (100 microg/g) that decreased temperature sensitivity, and (b) acclimation at high temperature (28 degrees C, 1 month) that also decreased temperature sensitivity. Temperature is probably acting through the neuroendocrine system, and ultimately interacting with steroid hormones in their effects upon EOD waveform.     

Distinct age and landscape influence on two reservoirs under the same climate

With the purpose of finding out whether different landscape occupation could affect water quality in two reservoirs of distinct age and subjected to the same climatic influence, several factors were investigated in a study lasting from January 2000 till December 2001. Total phosphorus, orthophosphate, chlorophyll a concentrations and water colour were determined monthly in winter and biweekly in summer, in two reservoirs located in the Portuguese part of River Douro catchment. Complementarily, variables such as nitrate, ammonium ion and ammonia gas, as well as water temperature, dissolved oxygen, conductivity, and transparency were measured. Trophic state of both reservoirs was assessed by computation of Carlson's Trophic State Index. The potential allochthonous sources of phosphorus and nitrogen to both reservoirs were identified and estimated. Differences between reservoirs were found for conductivity, water temperature, transparency and water colour. According to Carlson's Trophic State Index both reservoirs were classified as meso-eutrophic from winter to the beginning of summer, and as eutrophic from this period onwards. Intrinsic factors such as age of reservoir, organic matter inputs from decomposition of flooded terrestrial vegetation and exposure of littoral sediments to cycles of drying and wetting, as well as extrinsic factors such as grazing and frequent land fires, can explain the trophic state of S. Serrada Reservoir. Allochthonous sources of nutrients originated from agriculture and grazing in the catchment area, and recreational activities in the reservoir probably are the factors with greatest influence on Azibo Reservoir trophic state. Based upon the obtained data, management measures are suggested to prevent further eutrophication and water quality degradation in both reservoirs.     

Comparison of the thermal stability characteristics of native and deglycosylated ovine pituitary lutropin

The receptor binding, immunological and biological activities of native ovine lutropin were almost completely eliminated when aqueous solutions of the hormone were kept in a boiling water bath for 30 or 60 min. Similar exposure of chemically deglycosylated lutropin revealed that this preparation was relatively more stable to heat treatment. The conformational features of deglycosylated lutropin required for receptor binding and immunological activity were significantly retained after thermal treatment. The heated deglycosylated lutropin solution still retained its ability to antagonize cyclic AMP accumulation stimulated by the native hormone in rat testicular interstitial cells. Specificity of receptor (lutropin) binding or inhibitory activity was not lost by heating of deglycosylated lutropin as revealed by lack of an effect in follitropin radio-receptor assays.     

Large Thermal Conductivity Differences between the Crystalline and Vitrified States of DMSO with Applications to Cryopreservation

Thermal conductivity of dimethyl-sulfoxide (DMSO) solution is measured in this study using a transient hot wire technique, where DMSO is a key ingredient in many cryoprotective agent (CPA) cocktails. Characterization of thermal properties of cryoprotective agents is essential to the analysis of cryopreservation processes, either when evaluating experimental data or for the design of new protocols. Also presented are reference measurements of thermal conductivity for pure water ice and glycerol. The thermal conductivity measurement setup is integrated into the experimentation stage of a scanning cryomacroscope apparatus, which facilitates the correlation of measured data with visualization of physical events. Thermal conductivity measurements were conducted for a DMSO concentration range of 2M and 10M, in a temperature range of -180°C and 25°C. Vitrified samples showed decreased thermal conductivity with decreasing temperature, while crystalline samples showed increased thermal conductivity with decreasing temperature. These different behaviors result in up to a tenfold difference in thermal conductivity at -180°C. Such dramatic differences can drastically impact heat transfer during cryopreservation and their quantification is therefore critical to cryobiology.     

Limitations of microscopy to differentiate Plasmodium species in a region co-endemic for Plasmodium falciparum, Plasmodium vivax and Plasmodium knowlesi

Background

The question whether Plasmodium falciparum infection affects the fitness of mosquito vectors remains open. A hurdle for resolving this question is the lack of appropriate control, non-infected mosquitoes that can be compared to the infected ones. It was shown recently that heating P. falciparum gametocyte-infected blood before feeding by malaria vectors inhibits the infection. Therefore, the same source of gametocyte-infected blood could be divided in two parts, one heated, serving as the control, the other unheated, allowing the comparison of infected and uninfected mosquitoes which fed on exactly the same blood otherwise. However, before using this method for characterizing the cost of infection to mosquitoes, it is necessary to establish whether feeding on previously heated blood affects the survival and fecundity of mosquito females.

Methods

Anopheles gambiae M molecular form females were exposed to heated versus non-heated, parasite-free human blood to mimic blood meal on non-infectious versus infectious gametocyte-containing blood. Life history traits of mosquito females fed on blood that was heat-treated or not were then compared.

Results

The results reveal that heat treatment of the blood did not affect the survival and fecundity of mosquito females. Consistently, blood heat treatment did not affect the quantity of blood ingested.

Conclusions

The study indicates that heat inactivation of gametocyte-infected blood will only inhibit mosquito infection and that this method is suitable for quantifying the fitness cost incurred by mosquitoes upon infection by P. falciparum.