The effects of low dose (less than 1 Rad) X-rays on the erythropoietic marrow

Adult female Sprague-Dawley rats were exposed (200 kvp X-rays) to whole body doses of 22-1320 mrad and examined for changes in the level of red blood cell precursors (RBCp) in the marrow at 5–30 weeks post-irradiation, under nonbled and phlebotomy-induced anemic stress conditions. Increases in the RBCp %, RBCp/mg marrow, and RBCp/skeleton under nonbled conditions, and a suppressed erythroid response to an induced anemia, were found after acute doses in the range of at least 70 mrad. Dosages of 22 or 44 mrad that induced no measurable changes when applied only once were found to be effective when they were employed 4 or 2 times/week, respectively. The results suggested the presence of a linear-quadratic dose-response relationship in which the quadratic function exists between 88 and 981 mrad, and the linear dependency, below 88 mrad.     

Nontransferrin-bound Iron in Serum of Patients Receiving Bone Marrow Transplants

Nontransferrin-bound iron (NTBI) and other parameters of iron status were measured in 40 patients undergoing bone marrow transplantation (BMT) prior to conditioning therapy (between day −10 and −7), at the time of BMT (day 0), and 2 weeks later (day +14). Serum iron and transferrin saturation values were normal before conditioning therapy. At day 0 serum iron values were high and median transferrin saturation was 98% (changes in the values of both serum iron and transferrin saturation, p < .0001). Transferrin saturation values were still elevated 2 weeks posttransplant (day +14 vs. baseline values, p = .0001). Starting at low NTBI levels pretransplant (median 0.4 , range 0–4.2 , controls: ≤ 0.4 ), all patients revealed high levels on day 0 (median 4.0 , range 1.9–6.9 , p < .0001) and 2 weeks posttransplant (median 2.7 , range 0–6.2 , p < .0001). These observations indicate that the plasma iron pool in patients undergoing BMT increases to a level at which the normal ability to sequestrate iron becomes exhausted and considerable amounts of NTBI appear in serum. This “free” form of iron can mediate the production of reactive oxygen species and may cause organ toxicity in the early posttransplantation period. © 1997 Elsevier Science Inc.     

The role of mechanics in actin stress fiber kinetics

The dynamic responses of actin stress fibers within a cell's cytoskeleton are central to the development and maintenance of healthy tissues and organs. Disturbances to these underlie a broad range of pathologies. Because of the importance of these responses, extensive experiments have been conducted in vitro to characterize actin cytoskeleton dynamics of cells cultured upon two-dimensional substrata, and the first experiments have been conducted for cells within three-dimensional tissue models. Three mathematical models exist for predicting the dynamic behaviors observed. Surprisingly, despite differing viewpoints on how actin stress fibers are stabilized or destabilized, all of these models are predictive of a broad range of available experimental data. Coarsely, the models of Kaunas and co-workers adopt a strategy whereby mechanical stretch can hasten the depolymerization actin stress fibers that turn over constantly, while the models of Desphande and co-workers adopt a strategy whereby mechanical stress is required to activate the formation of stress fibers and subsequently stabilize them. In three-dimensional culture, elements of both approaches appear necessary to predict observed phenomena, as embodied by the model of Lee et al. After providing a critical review of existing models, we propose lines of experimentation that might be able to test the different principles underlying their kinetic laws.     

The protective effects of XH‐105 against radiation‐induced intestinal injury

Radiation‐induced intestinal injury is one of the major side effects in patients receiving radiation therapy. There is no specific treatment for radiation enteritis in the clinic. We designed and synthesized a new compound named XH‐105, which is expected to cleave into polyphenol and aminothiol in vivo to mitigate radiation injury. In the following study, we describe the beneficial effects of XH‐105 against radiation‐induced intestinal injury. C57BL/6J mice were treated by gavage with XH‐105 1 hour before total body irradiation (TBI), and the survival rate was monitored. Histological changes were examined, and survival of Lgr5⁺ intestinal stem cells Ki67⁺ cells, villi⁺ enterocytes and lysozymes was determined by immunohistochemistry. DNA damage and cellular apoptosis in intestinal tissue were also evaluated. Compared to vehicle‐treated mice after TBI, XH‐105 treatment significantly enhanced the survival rate, attenuated structural damage of the small intestine, decreased the apoptotic rate, reduced DNA damage, maintained cell regeneration and promoted crypt proliferation and differentiation. XH‐105 also reduced the expression of Bax and p53 in the small intestine. These data suggest that XH‐105 is beneficial for the protection of radiation‐induced intestinal injury by inhibiting the p53‐dependent apoptosis signalling pathway.     

植物铁吸收、转运和调控的分子机制研究进展

铁是植物正常生命活动所必需的微量矿质元素,铁离子的吸收、转运和利用是一个复杂的过程,很多基因参与了这一过程。本文对近10年来发现和分离的参与植物铁吸收、转运及调控的基因研究进展进行了综述。根据最近的研究结果,提出了植物控制铁吸收的分子调控模式(机理I)。     

Study of sodium homeostasis in blood in whole body gamma-irradiated rats

Adult male rats were subjected to whole body irradiation of 400 and 1000 rads and sodium homeostasis in blood was studied on the 1st, 4th and 7th days after exposure. A significant decrease in red cell adenosine triphosphatase, progressive loss of erythrocytic potassium and alteration in influx and efflux of sodium-22 in red cellsin vitro were observed in these rats.     

河西走廊土地利用/覆盖变化的景观生态效应——以肃州绿洲为例

近来,在土地利用／覆被变化研究中,都纷纷结合景观格局变化分析模型来研究其空间结构变化趋势及其生态效应,以期为土地持续利用规划设计提供依据。景观格局及其变化既是各种干扰因素相互作用的结果,又影响着区域的生态过程。运用景观生态学原理,借助GIS技术(Arc GIS8．1)和Fragstas 3．3软件,基于1988、2000年Landsat5的4、3、2(RGB)波段合成影像解译结果,对河西走廊中西段肃州绿洲LUCC及其景观生态效应进行了研究。结果表明：(1)受自然地理要素的影响,景观类型空间分布表现出明显的区域差异。耕地主要分布于水系两岸和河流冲积扇;草地主要分布于祁连山地及绿洲边缘;林地主要分布于河流两岸、祁连山北坡一带;戈壁、沙漠广泛分布于绿洲之间,景观格局呈现出以戈壁为基质的戈壁、绿洲、沙漠相间分布的态势;(2)各土地利用类型及景观格局指数均发生了重要变化,耕地、水域明显增加,城镇用地和农村居民点也逐步增加,草地、林地和未利用地呈减少趋势,尤其是高覆盖度草地全部消失;(3)斑块破碎化程度在减小,异质性也在减小,但生态环境质量仍在下降,表现为大部分草地、林地被开垦为耕地,降低了绿洲维护生态平衡的能力,加大了干旱绿洲业已超负的水资源载荷;(4)景观中斑块优势度在减小,斑块类型在景观中趋于均匀分布,异质性的减小和均质化发展必然导致景观稳定性的降低;(5)林地和草地边缘效应降低,使其对周围斑块类型的影响相应减小,原有的景观生态功能减弱;相反,水体、盐碱地和裸地边缘效应有所增强,盐碱地和裸地等对景观发展影响的增强则是景观退化的表现。     

Interactive effects of predation risk and conspecific density on the nutrient stoichiometry of prey

The mere presence of predators (i.e., predation risk) can alter consumer physiology by restricting food intake and inducing stress, which can ultimately affect prey‐mediated ecosystem processes such as nutrient cycling. However, many environmental factors, including conspecific density, can mediate the perception of risk by prey. Prey conspecific density has been defined as a fundamental feature that modulates perceived risk. In this study, we tested the effects of predation risk on prey nutrient stoichiometry (body and excretion). Using a constant predation risk, we also tested the effects of varying conspecific densities on prey responses to predation risk. To answer these questions, we conducted a mesocosm experiment using caged predators (Belostoma sp.), and small bullfrog tadpoles (Lithobates catesbeianus) as prey. We found that L. catesbeianus tadpoles adjust their body nutrient stoichiometry in response to predation risk, which is affected by conspecific density. We also found that the prey exhibited strong morphological responses to predation risk (i.e., an increase in tail muscle mass), which were positively correlated to body nitrogen content. Thus, we pose the notion that in risky situations, adaptive phenotypic responses rather than behavioral ones might partially explain why prey might have a higher nitrogen content under predation risk. In addition, the interactive roles of conspecific density and predation risk, which might result in reduced perceived risk and physiological restrictions in prey, also affected how prey stoichiometry responded to the fear of predation.     

Iron requirement for and effects of promoters and inhibitors of ethylene action on stimulation of Fe(III)-chelate reductase in roots of strategy I species

Stimulation of root Fe(III) reductase activity by iron additions to iron-deficient growth media may be the result of iron activation of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase required for ethylene biosynthesis. Two different ethylene inhibitors, aminooxyacetic acid (AOA) (20 m; ACC synthase inhibitor) and cobalt (3 m CoCl₂; ACC oxidase inhibitor), were used to study the effects of iron supply and cobalt inhibition on ethylene action in controlling the activity of Fe(III)-chelate reductase in pea (Pisum sativum L.) roots. Supplying 20 gm m Fe(III)-N,N-ethylenebis[2-(2-hydroxypheyl)-glycine [Fe(III)-EDDHA] to either cobalt-treated, iron-deficient Sparkle (normal parent) or E107 (brz mutant genotype) pea seedlings reversed the negative effects of cobalt on root Fe(III)-reductase activity. Re-supplying 20 m Fe(III)-EDDHA to iron-deficient, AOA-treated seedlings did not enhance root Fe(III)-reductase. Apparently, cobalt competes with iron for the active site in ACC oxidase during ethylene synthesis. Inhibition of root reductase activity by cobalt treatment lowered manganese, zinc, magnesium and potassium content of mutant E107 pea seedlings. In contrast, iron enhancement of root reductase activity in iron-deficient, cobalt-treated E107 seedlings resulted in higher seedling accumulations of manganese, zinc, magnesium and potassium. These results support the hypothesis that root cell plasma membrane reductase activity plays a role in cation uptake by root cells.     

Purification,electrophoretic behavior,and kinetics of iron release of liver ferritin of Dasyatis akajei

From the liver of fish Dasyatis akajei, ferritin has been isolated by thermal denaturation and ammonium sulfate fractionation and then further purified by anion exchange chromatography and gel exclusion chromatography. The molecular weight of the liver ferritin of D. akajei (DALF) was measured to be 400 kDa by PAGE. Moreover, SDS-PAGE experimentation indicates that protein shell of DALF consists of the H and L subunits with molecular weight of 18 and 13 kDa, respectively. Using isoelectric focusing with pH ranging from 5.0 to 6.0, the ferritin purified by the PAGE exhibited three bands with different pI values in the gel slab. Diameters of the protein shell and iron core were also investigated by transmission electron microscope and determined to be 10–12 nm and 5–8 nm, respectively. A kinetic study of DALF reveals that the rate of self-regulation of the protein shell rather than the complex surface of the iron core plays an important role in forming a process for iron release with mixed orders.     

束缚浸水应激对大鼠肝胆汁分泌的影响及其作用机制的研究

目的：通过研究束缚浸水应激对大鼠肝胆汁分泌的影响,探讨其作用机制。方法：实验分6组（n=8）：A组：室温下单纯束缚＋生理盐水;B组：束缚浸水应激＋生理盐水;C组：室温下单纯束缚＋阿托品;D组：束缚浸水应激＋阿托品;E组：室温下单纯束缚＋酚妥拉明;F组：束缚浸水应激＋酚妥拉明。结果：与A组比较,B组肝胆汁分泌量显著减少（P〈0．05）,pH值显著升高（P〈0．01）;与A组比较,C组肝胆汁分泌量变化不明显,只有微量减少：E组与A组相对照肝胆汁分泌量无明显变化,但也有微量减少。与B组比较,D组肝胆汁分泌量有明显变化（P〈0．05）,肝胆汁pH无明显变化;F组与B组对照其肝胆汁分泌量有明显变化（P〈0．05）,肝胆汁pH无明显变化;D组与F组对照肝胆汁分泌量无明显变化,肝胆汁pH无明显变化。结论：束缚浸水应激对大鼠肝胆汁分泌有明显地抑制作用。浸水应激组肝胆汁的分泌量明显减少,肝胆汁的pH明显升高;迷走神经、交感神经在室温单纯束缚的情况下对肝胆汁的分泌影响较小,而在束缚浸水的情况下迷走神经、交感神经对肝胆汁的分泌有较显著的影响（P〈0．05）。     

Some effects of time,temperature and feeding on infection rates with Babesia bovis and Babesia bigemina in Boophilus microplus larvae

Dalgliesh R. J. and Stewart N. P. 1982. Some effects of time, temperature and feeding on infection rates with Babesia bovis and Babesia bigemina in Boophilus microplus larvae. International Journal for Parasitology12: 323–326. Percentages of larval ticks in which Babesia bovis and B. bigemina parasites could be detected (infection rates) were determined after the larvae had been exposed to temperatures between 9°C and 27°C for periods of 1–35 days and then either fed on calves or heated at 37°C to stimulate babesial development. Infection rates with both species increased during 2–4 weeks after the larvae hatched, regardless of the temperature of exposure. Infection rates with B. bovis were higher after exposure of larvae to 14°C than to 27°C. This effect was less pronounced with B. bigemina. Infection rates were higher in fed larvae than in unfed, ‘heat stimulated’ larvae. The findings indicate that infected larval ticks become more efficient vectors of Babesia during the first 2–4 weeks after hatching and that repeated sampling of a tick population is necessary to determine valid infection rates.     

抑制浓度下锰铁对啤酒废酵母产LYCD活力影响

目的:探讨锰铁离子对啤酒废酵母产生活性酵母细胞衍生物(LYCD)的活力影响.方法:以啤涌废酵母为研究对象、以废液为培养基,在生长抑制浓度下,分别研究了锰、铁离子的作用浓度与时间对啤酒废酵母产生LYCD的活力影响.结果:废酵母在废液中培养28h可达到对数生长期;当废液中Mn~(2+)、Fe~(3+)浓度分别达到200mg/L、50mg/L时可对废酵母产生生长抑制;当Mn~(2+)、Fe~(3+)的作用浓度分别为220mg/L、60mg/L、应激时间分别是25、45min时,啤酒废酵母产的LYCD活性强.结论:应激培养基中金属离子Mn~(2+)、Fe~(3+)达到一定浓度,在一定时间下可使废酵母产生强活力的LYCD.     

片断化森林的边缘效应与自然保护区的设计管理

森林片断化引起了森林边缘物理环境与生物的变化。从森林边缘向林内,光辐射,温度、湿度、风等因素发生改变,这些反过 边缘上和边缘附近的生物产生极其重要的影响。有些研究表明,生物与非生物存在明显的边缘－核心的变化梯度,而有些则没有,除了影响边缘效应的客观因素（如边缘的取向、地势、年龄等）外,主观因素对这缘效应也有影响。边缘对生物与非生物的影响因片断化森林的面积、形状以及与其他森林片连接程度的不同而不同,     

钾对番红花球茎膨大的生理生态效应

名贵中药番红花球茎的大小是决定其入药器官—柱头多少的关键,用4个不同K水平的营养液培养番红花,结果表明,随着施钾水平的提高,叶片中的钾含量、叶绿素含量、ATP相对含量及叶片净光合速率也相应提高,使得叶片作为“代谢源”的能力加强．随着施钾水平提高,新球茎富集钾的能力、可溶性糖含量、Vc含量和蛋白质含量也增加,致使新球茎作为“代谢库”的功能也增强,球茎膨大速率加快,本文对钾元素通过加强“源”和“库”的功能来提高番红花球茎膨大速率的机理进行探讨,为番红花的进一步研究与利用提供了新的依据。     

In vivo and in vitro effects of aluminum treatment on rat liver mitochondrial function

This study examines the effect on mitochondrial respiration and permeability of in vivo and in vitro aluminium (Al) exposure. Rats were treated intraperitoneally with AlCl₃ to achieve serum and liver Al concentrations comparable to those seen in Al-related disorders. Mitochondria isolated from Al-treated rats had higher (p<0.01) Al concentration, lower (p<0.05) state 3 respiration, respiratory control (RCR), and ADP/O ratio (succinate substrate), and greater passive swelling in 100 mM KCl or 200 mM NH₄NO₃ than controls. The in vitro addition of Al (0–180 μM) to mitochondria from normal rats also decreased (p<0.01) state 3 respiration, RCR, and ADP/O and stimulated passive swelling in KCl and NH₄NO₃ at 42–180 μM Al. These studies show that Al depresses mitochondrial energy metabolism and increases membrane permeability. The toxicity associated with Al may be related to its effect on mitochondria.     

Projected effects of Climate‐change‐induced flow alterations on stream macroinvertebrate abundances

Global change has the potential to affect river flow conditions which are fundamental determinants of physical habitats. Predictions of the effects of flow alterations on aquatic biota have mostly been assessed based on species ecological traits (e.g., current preferences), which are difficult to link to quantitative discharge data. Alternatively, we used empirically derived predictive relationships for species’ response to flow to assess the effect of flow alterations due to climate change in two contrasting central European river catchments. Predictive relationships were set up for 294 individual species based on (1) abundance data from 223 sampling sites in the Kinzig lower‐mountainous catchment and 67 sites in the Treene lowland catchment, and (2) flow conditions at these sites described by five flow metrics quantifying the duration, frequency, magnitude, timing and rate of flow events using present‐day gauging data. Species’ abundances were predicted for three periods: (1) baseline (1998–2017), (2) horizon 2050 (2046–2065) and (3) horizon 2090 (2080–2099) based on these empirical relationships and using high‐resolution modeled discharge data for the present and future climate conditions. We compared the differences in predicted abundances among periods for individual species at each site, where the percent change served as a proxy to assess the potential species responses to flow alterations. Climate change was predicted to most strongly affect the low‐flow conditions, leading to decreased abundances of species up to ?42%. Finally combining the response of all species over all metrics indicated increasing overall species assemblage responses in 98% of the studied river reaches in both projected horizons and were significantly larger in the lower‐mountainous Kinzig compared to the lowland Treene catchment. Such quantitative analyses of freshwater taxa responses to flow alterations provide valuable tools for predicting potential climate‐change impacts on species abundances and can be applied to any stressor, species, or region.     

Experimental evidence for root competition effects on community evenness in one of two phytometer species

AimsPlant–plant interactions, being positive or negative, are recognized to be key factors in structuring plant communities. However, it is thought that root competition may be less important than shoot competition due to greater size symmetry belowground. Because direct experimental tests on the importance of root competition are scarce, we aim at elucidating whether root competition may have direct or indirect effects on community structure. Indirect effects may occur by altering the overall size asymmetry of competition through root–shoot competitive interactions.     

茉莉酸甲酯诱导邻近番茄植株抗斜纹夜蛾的浓度和距离效应

茉莉酸甲酯(Methyl jasmonate, MeJA)与植物间的防御通讯密切相关,其挥发性强,可以在空气中传播而诱导邻近植物产生防御反应,为探明MeJA诱导邻近植株抗虫性的浓度和距离效应,本研究在大棚(长4 m×宽1 m×高1 m)进口处喷以不同浓度MeJA,检测离气味源60 cm、120 cm、180 cm、240 cm和300 cm远的番茄植株叶片多酚氧化酶(Polyphenol oxidase, PPO),过氧化物酶(Peroxidase, POD)和脂氧合酶(Lipoxygenase, LOX)的活性以及斜纹夜蛾幼虫取食不同处理番茄植株叶片后的体重增长率,研究结果表明1 mmol/L和10 mmol/L MeJA挥发物可以显著诱导增强邻近番茄植株叶片PPO,POD和LOX酶的活性,以离10 mmol/L MeJA气味源60 cm处植株叶片的酶活性最高,并随着距离的增加而呈降低的趋势;取食60 cm和300 cm对照组植株叶片的斜纹夜蛾幼虫其体重增长率没有显著差异,然而1 mmol/L和10 mmol/L MeJA处理下,取食300 cm处植株叶片的斜纹夜蛾幼虫其体重增长率显...