The combined effect of lymphokine activated killer cell and radiation therapy on rat brain tumorin vitro

Thein vitro effect of a combined treatment with lymphokine activated killer (LAK) cell and radiation therapy on rat brain tumor was examined using⁵¹Cr release assay. The tumor cell-line used in this experiment was 9L rat brain tumor derived from a Fischer 344 rat. LAK cells were obtained by culturing rat lymphocytes with recombinant human interleukin 2 for at least 3 days. The cytotoxic activity of the LAK cells was examined by⁵¹Cr release assay. Irradiation was done by exposing the microtiter plate in which the¹⁵Cr labeled 9L cells and LAK cells were cultured to a¹³⁷Cs gamma cell unit. Without irradiation, there was 18% cytotoxicity in the 1:100 tumor-to-LAK cell ratio specimen after 24 hrs cocultivation. However, if 5 Gy of irradiation was given, followed by 12 hrs incubation, the cytotoxicity was enhanced significantly at the same cell ratio (30%). This enhancement effect was the most prominent when the cell ratio was 1:100 and the irradiation dose was 5 Gy. To generate the enhancement effect, an incubation time of over 8 hrs both before and after irradiation was required. The supernatant of the LAK cells showed 19.8% and 11.4% cytotoxicity with and without irradiation, respectively. This result indicates the participation of a cytotoxic factor released from LAK cells.This work is supported in part by grant from Univeristy of Tsukuba Project Research.     

Superoxide production by thylakoids during chilling and its implication in the susceptibility of plants to chilling-induced photoinhibition

Factors influencing the rate of superoxide (O ₂ ^- ) production by thylakoids were investigated to determine if increased production of the radical was related to injury induced by chilling at a moderate photon flux density (PFD). Plants used were Spinacia oleracea L., Cucumis sativus L. and Nerium oleander L. grown at either 200° C or 45° C. Superoxide production was determined by electron-spin-resonance spectroscopy of the (O ₂ ^- )-dependent rate of oxidation of 2-ethyl-1-hydroxy-2,5,5-trimethyl-3-oxazolidine (OXANOH) to the corresponding oxazolidinoxyl radical, OXANO ·. For all plants, the steady-state rate of O ₂ ^- production by thylakoids, incubated at 25° C and 350 mol photon · m^–2 · s^–1 (moderate PFD) with added ferredoxin and NADP, was between 7.5 and 12.5 mol · (mg chlorophyll)^–1 · h^–1. Incubation at 5° C and a moderate PFD, decreased the rate of O ₂ ^- production 40% and 15% by thylakoids from S. oleracea and 20° C-grown N. oleander, chillinginsensitive plants, but increased the rate by 56% and 5% by thylakoids from C. sativus and 45° C-grown N. oleander, chilling-sensitive plants. For all plants, the addition of either ferredoxin or methyl viologen increased the rate of O ₂ ^- -production at 25° C by 75–100%. With these electron acceptors, lowering the temperature to 5° C caused only a slight decrease in O ₂ ^- production. In the absence of added electron acceptors, thylakoids produced O ₂ ^- at a rate which was about 45% greater than that when ferredoxin and NADP were present. The addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea reduced O ₂ ^- production under all conditions tested. The results show that the rate of O ₂ ^- production increases in thylakoids when the rate of electron transfer to NADP is reduced. This could explain differences in the susceptibility of thylakoids from chilling-sensitive and chilling-insensitive plants to chilling at a moderate PFD, and is consistent with the proposal that O ₂ ^- production is involved in the injury leading to the inhibition of photosynthesis induced under these conditions.Abbreviations Chl chlorophyll - DCMU 3-(3,4-dichlorophen-yl)-1,1-dimethylurea - Fd ferredoxin - MV methyl viologen - 20°oleander Nerium oleander grown at 20° C - 45°-oleander N. oleander grown at 45° C - OXANOH 2-ethyl-1-hydroxy-2,5,5-tri-methyl-3-oxazolidine - PFD photon flux density (photon fluence rate) - TEMED tetramethyl ethylenediamine We would like to thank R.T. Furbank, R.S.B.S., Australian National University, Canberra, A.C.T., and C.B. Osmond, now of Duke University, Durham, N.C., USA, for the gift of ferredoxin, R.A.J.H. was supported by a Commonwealth Postgraduate Research Award.     

Weak field influence on biomolecular changes

Model equations for the kinetics of the synthesis and decay of molecular aggregates are used to show the high sensitivity of equilibrium concentrations of high-molecular aggregates to external radiation. This phenomenon is used to explain the effects of low-intensity microwave fields on the functioning of biological systems. The experimental results on the influence of SHF-radiation on ferricyanide reduction by erythrocytes are interpreted in detail.     

Foundations of vectorial metabolism and osmochemistry

Chemical transformations, like osmotic translocations, are transport processes when looked at in detail. In chemiosmotic systems, the pathways of specific ligand conduction are spatially orientated through osmoenzymes and porters in which the actions of chemical group, electron and solute transfer occur as vectorial (or higher tensorial order) diffusion processes down gradients of total potential energy that represent real spatially-directed fields of force. Thus, it has been possible to describe classical bag-of-enzymes biochemistry as well as membrane biochemistry in terms of transport. But it would not have been possible to explain biological transport in terms of classical transformational biochemistry or chemistry. The recognition of this conceptual asymmetry in favour of transport has seemed to be upsetting to some biochemists and chemists; and they have resisted the shift towards thinking primarily in terms of the vectorial forces and co-linear displacements of ligands in place of their much less informative scalar products that correspond to the conventional scalar energies. Nevertheless, considerable progress has been made in establishing vectorial metabolism and osmochemistry as acceptable biochemical disciplines embracing transport and metabolism, and bioenergetics has been fundamentally transformed as a result.     

1H and15N resonance assignments and secondary structure of the human thioredoxin C62A,C69A,C73A mutant

Summary The complete assignment of¹H and¹⁵N backbone resonances and near-complete¹H side-chain resonance assignments have been obtained for the reduced form of a mutant of human thioredoxin (105 residues) in which the three non-active site cysteines have been substituted by alanines: C62A, C69A, C73A. The assignments were made primarily on the basis of three-dimensional.¹⁵N-separated nuclear Overhauser and Hartmann-Hahn spectroscopy, in conjunction with two-dimensional homonuclear and heteronuclear correlation experiments. Based on comparisons of short-range and interstrand nuclear Overhauser effects, patterns of amide exchange, and chemical-shift differences, the structure appears essentially unchanged from that of the previously determined solution structure of the native protein [Forman-Kay. J.D. et al. (1991)Biochemistry, 30, 2685–2698). An assay for thioredoxin shows that the C62A, C69A, C73A mutant retains activity. The assignment of the spectrum for this mutant of human thioredoxin constitutes the basis for future studies aimed at comparing the details of the active-site conformation in the reduced and oxidized forms of the protein.     

Disulfide bridges in tomato pectinesterase: variations from pectinesterases of other species; conservation of possible active site segments.

Analysis of tomato pectinesterase by carboxymethylation, with and without reduction, shows that the enzyme has two intrachain disulfide bridges. Analysis of fragments obtained from the native enzyme after digestion with pepsin identified bridges connecting Cys-98 with Cys-125, and Cys-166 with Cys-200. The locations of disulfide bridges in tomato pectinesterase are not identical to those in three distantly related pectinesterases (18-33% residue identities) from microorganisms. However, one half-Cys (i.e., Cys-166) position is conserved in all four enzymes. Sequence comparisons of the overall structures suggest a special importance for three short segments of the entire protein. One segment is at the N-terminal part of the tomato pectinesterase, another in the C-terminal portion near the distal end of the second disulfide loop, and the third segment is located in the central part between the two disulfide bridges. The latter segment, encompassing only 40 residues of the entire protein, appears to high-light a functional site in a midchain segment.     

互花米草人工植被生态效益和经济效益的初步研究

前言在我国海涂中被日潮淹没的中、低潮带,天然生长的高等植物种类比较贫乏,分布面积也较小,许多中低潮带海滩为光滩裸地。为了绿化海滩、保护海滩,提高海滩生态系统的初级生产力,我国在1963年和1978年分别从英国     

电离辐射引起胃排空延迟机理的初步探讨

本文观察了800rad照射后胃肠肌电的变化及切斷内脏神经与电刺激迷走神经对官的影响,初步分析了电离辐射引起胃排空延迟的机理。结果是:800rad照后大鼠胃肠肌电的峰波平均振幅胃幽部窦部照后1小时至第4天明显降低(P<0.05);幽门括约肌政变不大;十二指肠球部照后第3～7天明显下降(P<0.01)。切断内脏神经后照射大鼠胃肠肌电的峰波平均振幅胃幽门窦部变化不大,幽门括约肌照后1小时至第5天明显升高(P<0.05),十二指肠球部照后第3～7天明显下降(P<0.05)。800rad照后第4天大鼠胃对电刺激迷走神经的反应性明显降低(P<0.01)。上述结果表明:照后胃排空延迟的原因不仅与神经-体液调节紊乱有关,而且与射线损伤了平滑肌,使其兴奋性暂时的功能性降低有关。此外照后由于十二指肠球部运动的变化而使内感受器对胃运动的调节发生紊乱也是值得重视的因素。     

Radiation chemistry of a multicomponent aqueous system relevant to chemistry of cometary nuclei

Summary We have examined a water-dominated multicomponent system after irradiation in the multimegarad dose range with gamma rays from a⁶⁰Co source at both 77 and 310 K. The constituents were simple organic compounds in the proportions in which they appear in a dense interstellar cloud: HCN/CH₃OH/CH₃CN/C₂H₅CN/HCOOH=10.60.20.10.05. The total amounts were adjusted to correspond to a carbon to nitrogen ratio of 1.8 and a water content of about 50% in a cometary nucleus where the dust to volatiles ratio is 1; the total amount of CN-bearing compounds was taken to correspond to 0.4% of the cometary mass. In experiments at 310 K about 40 radiolytic products are identified, among them aldehydes and amino and carboxylic acids. Abundant polymeric material (M_w up to 80,000 daltons) is formed. The basic aspects of radiolysis of the liquid system are present also at 77 K, although at radiation-chemical yields that are lower by one to two orders of magnitude. We have considered the relevance of the present findings to the chemistry of a liquid-water core and the icy layers of a cometary nucleus.     

Radiation chemistry of an aqueous solution of glycine: compounds of interest to chemical evolution studies

Summary We have examined the radiolysis of an O₂-free aqueous solution of glycine at absorbed doses of⁶⁰Co gamma-radiation of up to 20 Mrad. At least 20 compounds are formed during radiolysis, among them several amino acids, an oligoamine, and the nitrogen-free polymers (M_w28,000 daltons). When dicyandiamide is present in the solution of glycine, various nitrogen-containing products, including some polymers (M_w12,000 daltons), are synthesized along with radiolytic products of glycine; polyglycines are not formed. We have determined the radiation-chemical yields of radiolytic-product formation and of decomposition of glycine, and have considered possible free-radical reactions leading to the radiation-induced changes observed.