Spin label partition in gamma-irradiated lysophosphatidylcholine-water systems

Summary Nonbilayer structures, as lysophospholipid micelles, can be produced in membranes by gamma irradiation. Interesting information on the gamma-ray effect on the lysophospholipid organization can be obtained by spin-label techniques. Variations of the TEMPO partition are appreciable, particularly in the range of the lipid thermotropic transition, even from relatively low doses. With increasing dose this transition becomes more and more complex and wider, according to the previous thermodinamic analysis.     

Biostimulation of HeLa cells by low-intensity visible light

Summary A culture of HeLa cells was subjected to concurrent and consecutive dichromatic irradiation with visible light of various wavelengths. Consecutive dichromatic irradiation in the sequence 760 nm+633 nm was found to stimulate the synthesis of DNA in the cells and that in the sequence 633 nm+760 nm to inhibit it. These effects reached their maxima when the time interval between the successive irradiation events came to (1⋎3) min. On the strength of these data it is supposed that in HeLa cells there may exist a photochromic, photoreversible pigment similar to photochrome. Based on the results of dichromatic irradiation with blue and red light, flavoproteins are being discussed as likely photoreceptors.

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Una cultura di cellule HeLa è stata sottoposta ad irradiazione dicromatica concomitante e consecutiva con luce visibile di varie lunghezze d'onda. Si è trovato che l'irradiazione dicromatica consecutiva nella sequenza 760 nm+633nm stimola la sintesi del DNA nelle cellule e quella nella sequenza 633 nm+760 nm la inibisce. Questi effetti raggiungono i valori massimi quando l'intervallo di tempo tra irradiazioni successive arriva a (1⋎3) min. Sulla base di questi dati si suppone che nelle cellule HeLa possa esistere un pigmento fotocromatico fotoreversibile simile al fotocromo. In base a questi risultati di radiazione dicromatico con luce blu e rossa, le flavoproteine sono discusse come fotorecettori similari.

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Резюме Проведено одновременное и последовательное дихромное облучение клеток НеЛа различными длинами волн видимой области спектра. Скорость синтеза ДНК стимулируется при последовательном облучении (760+633) нм и инлибирыется при последовательности (633+760) нм. Эффекты являются максимальными когда интервал между лблучениями составляет (1⋎3) мин. На основе зтих данных предполагается существование в клетках ХеЛа фотохромното фотообратимого питмента типа фитохрома. На основе данных о дихромном облученим и красным светом в качестве возможных фоторецепторов обсуждаются флавпротеиды.

     

Damage effects of γ-radiation on lipid bilayers

Summary The lipid composition of multi-lamellar vesicles of 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine exposed to¹³⁷Cs γ-rays depends on the absorbed dose. In fact,³¹P and¹H NMR analysis shows that four new molecular species are formed during the irradiation:a) 1-palmitoyl-sn-glycero-3-phosphorylcholine,b) 2-palmitoyl-sn-glycero-3-phosphorylcholine,c) glycerophosphorylcholine andd) free palmitic acid. Neglecting the speciesc), that is present only at high dose and in very small amount, the behaviour of molar fractionvs. dose is sublinear fora) andb), while ford) it is almost linear over all the dose range examined. The molecular and structural damage consequences onto the multi-lamellar vesicles, evidentiated by spin-labelling and DSC techniques, are discussed. It is clearly shown in particular, that the behaviour of the main transition does not depend on the concentration of the lysolecithins, but rather on that of the free palmitic acid, the role of which had previously been entirely neglected. The authors of this paper have agreed to not receive the proofs for correction.     

Analytical model of phototherapy for neonatal jaundice. Influence of bilirubin kinetics on skin colour during phototherapy

Summary Recent progress in diode-array detector technology and signal processing methods, and in the optical modelling of tissues allow: i) real-time, multispectral analysis of reflected spectra with relatively simple and compact devices; and ii) improved correlations between reflectance spectra and pigment distribution in tissues. Second-generation transcutaneous bilirubinometers relying on the changes in the optical properties of the skin at selected wavelengths due to changes in its optical components are being developed. To extend the use of transcutaneous bilirubinometry to the phototherapy cycle, the modelling of the complex mechanisms of bilirubin photochemistry and metabolism in the various body compartments is required. As a first step toward this aim, the influence of bilirubin photochemistry occurring during the initial stage of phototherapy on the reflectance spectrum of an icteric tissue is analysed. A four-layer model is assumed. The transformation of bilirubin into its configurational isomers is considered in detail, while the role of the structural isomer on bilirubin elimination is taken into account with a loss term in the equation of motion of bilirubin concentration. The phototherapeutic process makes the illumination in the bile pigment layer depend on time. However, in the specific cases here considered, this time variation is negligible, and the differential equations describing the time evolution of bile pigment concentrations can be solved in a closed form. The bilirubin kinetics produces significant changes of the diffuse reflectance spectra during phototherapy, and the difference of the colour after the phototherapeutic treatment of a known duration can be put in close correspondence with the model of the jaundiced skin and permits quantitative estimates of pigment concentrations.     

A molecular model for the line tension of lipid membranes

The line tension of a symmetric, lipid bilayer in its liquid-crystalline state is calculated on the basis of a molecular lipid model. The lipid model extends the opposing forces model by an expression for the conformational free energy of the hydrocarbon chains. We consider a membrane edge that consists of a perturbed bilayer covered by a section of a cylinder-like micelle. The structural rearrangement of the lipids implies an excess free energy which we minimize with respect to the cross-sectional shape of the membrane edge, including both the micellar and the bilayer region. The line tension is derived as a function of molecular lipid properties, like the lipid chain length or the head group interaction strength. We also relate it to the spontaneous curvature of the lipid layer. We find the line tension to become smaller for lipid layers that tend to curve more towards the hydrophobic core. Our predictions for the line tension and their relation to experimentally derived values are discussed. Received 2 January 2000     

On primary damage and secondary electron damage in heavy ion tracks in plastics

Despite many successful applications of non-photographic dielectric track detectors in numerous scientific and technological fields, the basic mechanisms of track formation and development are still rather unknown for these detectors. In this paper an attempt is made to estimate the relative importance for track formation in plastics of direct interactions of heavy charged particles and of events of their secondary electrons. Both classes of events are weighted rather differently in existent track formation models. The discussion is mainly based on results obtained from calculations on the spatial distribution of events along and around the paths of fast ions and of electrons.     

一种计算氩等离子物态方程的简单模型

将Thomas-Feimi统计模型电离势的数值结果进行函数逼近，给出一个便于近似数值求解的解析表达式和计算电离度的近似计算方法，计算了Ar元素LTE情况下的电离度和物态方程，结果与Saha模型的计算结果和实验结果符合较好.所提出的简单模型也适用于计算混合物物态方程，可以在电磁发射技术领域中的强电离等离子体中有广阔的应用前景. 关键词： 等离子体 物态方程 电离势 电离度     

Effects of cholesterol and azelaic acid in lecithin liposomes exposed to ELF fields: A thermodynamic and structural study

Summary In the present work some thermodynamic and structural aspects of electric-, magnetic- and electromagnetic-field interaction at 50 Hz with lecithin liposomes mixed with azelaic acid or cholesterol have been investigated by using differential scanning calorimetry and X-ray diffraction. Calorimetric scans and X-ray diffraction patterns show that no significant modifications of the two mixtures occur, except a little increase of the freezing temperature of the free water after exposure to electromagnetic field.     

氩等离子体物态方程的TF简化模型

对于高温高压下氩等离子体的电离度和物态方程,本文给出了一种基于Thomas-Feimi(TF)统计模型的简化计算新方法:首先将TF模型电离势的数值结果进行函数逼近,给出一个便于数值求解的计算电离度的近似计算方法,并由此计算了局部热动平衡下的氩等离子体在10～1000 eV高温范围内的物态方程.计算结果与国外报道的其他几种理论模型的计算结果均符合很好,与实验值也吻合较好.本文所提出的简单模型也适用于计算混合物物态方程,可以在电磁发射技术领域中的强电离等离子体中有更为广阔的应用前景.     

Percolation and spreading of damage in a simplified Kauffman model

A simplified version of the Kauffman cellular automaton is introduced. As in the usual Kauffman model, there is a transition between a frozen phase and a chaotic phase where damage may spread. We associate the onset of chaos in this model with a percolation transition of certain rules occurring in the model. It seems to be in a different universality class from the usual Kauffman cellular automaton.     

抗辐射能力量化设计方法

抗辐射能力表现为系统技术性能对辐射损伤的敏感程度。抗辐射能力是设计、生产出来的。抗辐射量化设计能力是抗辐射加固技术发展水平的重要标志。根据QMU（性能阈值、裕量和不确定度）的思想,提出量化抗辐射设计,第一要优化系统总体设计,为辐射损伤敏感的技术性能合理地分配裕量;第二要量化系统工作的辐射环境及其不确定度,量化在实际工作的辐射环境中,辐射损伤引起的系统及其器件和结构的技术性能变化和不确定度,综合优化抗辐射措施,确保技术性能变化及其不确定度被有效控制在分配的裕量范围内,最后量化加固设计效果,预测系统抗辐射能力。     

On the inverse problem in transcutaneous bilirubinometry

Summary Transcutaneous bilirubinometry based on reflectance spectroscopy technique requires the development of suitable optical models of icteric skin and the solution of the inverse problem to derive pigment concentrations from spectral measurements. An algorithm is presented which allows the evaluation of bilirubin concentration during phototherapy. The present analysis shows that quantitative evaluation of bile pigment concentrations during phototherapy can be obtained with a good degree of accuracy by an inverse best-fit procedure; moreover, the knowledge of pigment kinetics makes this method almost independent of other conditions of the skin. The present results refer to the initial part of the phototherapy cycle and are based on a simple model of icteric skin; they may help to extend the application range of commercial transcutaneus bilirubinometer and to investigate the photoconfigurational transient of phototherapy.     

空腔"黑体"辐射的简单模型及推论

建立了一个简单的模型来描绘空腔辐射中腔壁与辐射场的能量交换,由此可以得到空腔辐射平衡场能谱的性质,基尔霍夫定律,以及空腔与黑体的关系．     

Influence of skin optical losses on configurational photoisomerization of bilirubin during phototherapy

Summary Kubelka-Munk theory of radiation transfer in turbid media is applied to determine the influence of skin optical losses on the efficiency of phototherapy of neonatal hyperbilirubinemia. By using a multilayer model of the skin and a rate equation analysis of bilirubin photo-isomerization, the photon absorption rates of birilubin and of its configurational photoisomers and, in turn, the photoequilibrium concentrations and rise time are calculated for spectrally Gaussian light sources and fluorescent lamps used in phototherapy. It turns out that light absorption and scattering processes in the skin layers produce a 30 nm red-shift of the optimum value of the peak excitation wave-length of bilirubin absorption and photoequilibrium rise time. The comparative data on the phototherapeutical efficiency of different spectral regionsin vivo (Gunn rats and humans) are discussed.

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Riassunto L'influenza delle perdite ottiche cutanee sul rendimento della fototerapia dell'iperblirubinemia neonatale è investigata mediante l'impiego della teoria di Kubelka-Munk sulla propagazione della luce in mezzi torbidi. L'evoluzione temporale delle concentrazioni di bilirubina e dei suoi fotoisomeri configurazionali è studiata per mezzo delle equazioni di bilancio nel caso del modello a multistrati della cute, assumendo una sorgente con distribuzione spettrale gaussiana e i profili spettrali delle principali lampade fluorescenti usate clinicamente. I risultati indicano che l'assorbimento e la diffusione della luce negli strati cutanei sposta di circa 30 nm verso lunghezze d'onda maggiori il valore ottimale della lunghezza d'onda d'assorbimento della bilirubina e del tempo di fotoequilibrio. Si discutono comparativamente i dati sul rendimento foroterapeutico di diverse regioni spettraliin vivo (su ratti Gunn e uomo).

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Резюме Теория Кубелки-Мунка рационального переноса в мутной среде применяется для определения влияния оптических потерь в поверхностном слое на эффективность фототерапии. Используя многослойную модель кожи и анализ фотоизомеризации билирубина, вычисляются интенсивности поглощения фототонов билирубином и его конфигурационным фотоизомерами и, в свою очередь, фоторавновесные концентрации и времена возникновения для источников света с гауссовым спектром и для флуоресцентных ламп, используемых в фототерапии. Оказывается, что процессы поглощения и рассеяния света в поверхностных слоях кожи приводят к красному смещению 30 нм оптимальной величины длины волны для поглощения билирубином. Обсуждаются сравнительные данные об эффективности фототерапии в различных спектральных областях ?в естественных условиях?.

     

Collision damage processes due to energetic heavy ions in silver chloride

The optical absorption band induced by energetic heavy ions implanted into AgCl single crystals at 77°K must be connected with the formation of silver colloids. The experimental (primitization and E.P.R. spectra) and theoretical study, makes it possible to obtain an approximate value of cluster radius. The colloid concentration is correlated with nuclear stopping power. It is shown that the collision efficiency is modified by a chemical effect. Finally the conditions of cluster formation are analysed.     

Biostimulation of HeLa cells by low-intensity visible light

Summary The action spectra of low-intensity light in the range from 300 to 900 nm on the synthesis rate of nucleic acids in the culture of HeLa cells has been measured. The synthesis of DNA and RNA is stimulated in several spectral intervals with maxima nearby 400, 630, 680, 760 and 820 nm. The stimulation effect is very sensitive to the irradiation duration (light intensity) at a fixed dose. The dose that causes the maximal stimulation is approximately 10 times smaller in the near-UV blue region than in red-IR region.

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Riassunto Si è misurato lo spettro d’azione della luce a bassa intensità nell’intervallo da 300 a 900 nm sul tasso di sintesi degli acidi nucleici in culture di cellule HeLa. La sintesi di DNA ed RNA è stimolata in parecchi intervalli spetrali con massimi vicino a 400, 630, 680, 760 e 820 nm. L’effetto di stimolazione è molto sensibile alla durata d’irradiazione (intensità della luce) ad una dose fissa. La dose che causa la stimolazione massima è approssimativamente dieci volte piú piccola nella regione blu dell’ultravioletto vicino che nella regione del rosso-infrarosso.

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Резюме Измерен спектр действия низкоинтенсивного света в диапазоне (300⋎900) нм на скорость синтеза нуклеиновых кислот в культуре клеток HeLa 1.5 часа после облучения. Синтез ДНК и РНК стимулируется в несколбких спектральных интервалах с максимумами вблизи 400, 630, 680, 760 и 820 нм. Эффект стимуляции очень чувствителен к продолжительности облуения (интенсивности света) при фиксированной дозе. Доза, при которой наблюдается максимальная стимудяция, в несколько ваз меньше в ближнеи УФ-синей области с максимумом около 400 нм.

     

Physical and radiobiological parameters of proton beams up to 31 MeV

Summary Frequency distributions of energy deposition in microscopic tissue volumes determined by means of a ?Rossi type? proportional counter for 31, 12 and 8 MeV proton beams and, dose response curves for mortality and chromosome aberrations in cultured human cells exposed to the same beams are analysed with a view to determining suitable parameters to specify radiation quality. The behaviour of quantities LET,Z ^*2/β² and the microdosimetric parameter as a function of energy are compared with the corresponding behaviour of the most significant radiobiological parameters as mean lethal dose per targetD ₀, mean inactivation dose , intensity of chromosome aberrations, and dicentrics. It is shown that is the most suitable physical parameter to characterize the relative effectiveness of protons in the (8÷31) MeV range. Work partially supported by grant No. 8000165896 for the Finalized Project ?Tumor Growth Control?.     

Stimulation of E. coli growth by laser and incoherent red light

Summary The effect of low-intensity He−Ne laser radiation (λ=632.8 nm) and incoherent red light on DNA synthesis and cell division in Escherichia coli has been studied. It has been shown that the radiations of He−Ne laser (λ=632.8 nm) and filament lamp (λ=(631±4) nm) stimulate DNA synthesis and cell growth at doses of 10³ to 10⁴ J/m². The highest level of DNA synthesis is observed 10 min after irradiation and the difference in the numbers of irradiated and control cells is maximum 1 or 2 h after irradiation. The action spectrum of visible light on the growth rate of E. coli cells (from 560 nm to 640 nm) has been measured. The action spectrum has its maximum at (620±7) nm.

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Riassunto Si è studiato l'effetto della radiazione laser He−Ne a bassa intensità e della luce rossa incoerente sulla sintesi del DNA e sulla divisione della cellula in Escherichia coli. Si è mostrato che le radiazioni del laser He−Ne (λ=632.8 nm) e della lampada con filamento (λ=(631±4) nm) stimolano la sintesi del DNA e la crescita cellulare a dose di (10³⋎10⁴) J/m². Il piú alto livello di sintesi del DNA è osservato 10 min dopo l'irradiazione e la differenza nei numeri di cellule irradiate e di controllo è massima 1 o 2 ore dopo irradiazione. Si è misurato lo spettro d'azione della luce visibile sul rapporto di crescita delle cellule di E. coli (da 560 nm a 640 nm). Lo spettro d'azione ha il suo massimo a (620±7) nm.

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Резюме Изучалось влияние низконтенсивного излучения He−Ne лазэра (λ=632.8 нм) и некогерентного красного света на синтез ДНК и клеточное деление в клэтках Escherichia coli. Показано, что как излучение He−Ne лазера, так и лампьи накаливания (λ=(631±4) нм) стимулирует синтез ДНК и клетпчное леление в дозах (10⁻²⋎10⁻³) Джм². Наиболее вьисокий уровень синтеза ДНК наблюлаеттся чурез 10 минут после облучения, скорость клеточногхого делэния максимальна через (1⋎2) часа после облучения. Измерен спектр действия видимого света на скрость деления клеток E. coli от λ=560 нм до λ=640 нм. Спектр действия имеет максимум при (620±7) нм.