南方森林雨雪冰冻灾害的特征

近年来极端气候事件频发,各地的雨雪冰冻灾害受到广泛关注。极端的雨雪冰冻灾害作为一个重要的扰动因子,对森林生态系统造成重大影响,尤其是在中国冰雪天气少有发生的南亚热带地区。2008年1-2月中国南方遭受了一场低温雨雪冰冻综合性极端天气灾害,其持续时间长,影响范围广,对中国南方森林造成了严重的损害。国内对此次雨雪冰冻灾情概况、林木受损情况以及雨雪冰冻灾害程度的影响因素等方面开展了大量研究,而现有的研究对受损林木评定的标准主观、粗略不全或是概念混淆,造成各研究结果难以比较。为明晰分类标准及相关概念,本文在总结雨雪冰冻灾害发生的气候与生物学特点、整合前人研究结果的基础上,提出雨雪冰冻灾害中林木生理冻害分类标准以及林木机械损伤分类标准,为相关研究提供参考依据。同时,总结分析雨雪冰冻灾害中导致森林受损的各影响因素,并将众多的因素总结归纳为影响凝雪冰凌重量及林木自身抵抗力2个方面。最后,针对灾害的影响因素以及灾后森林易发生的次生灾害,提出灾后森林恢复与重建的建议。     

病毒感染与宿主细胞DNA损伤应答

病毒感染宿主细胞后,利用细胞内的营养物质和原料进行复制和增殖,同时能引起宿主细胞启动抗病毒免疫应答的防御机制。此外,近年来的研究还表明病毒感染能够引起宿主细胞的DNA损伤应答,该反应是细胞另一种防止病毒入侵的自我保护机制。同时发现,病毒在长期进化过程中形成了不同的机制来对抗宿主细胞的DNA损伤应答,从而消除细胞对其复制和繁殖产生的不利影响。因此,研究和阐述病毒感染后引起宿主细胞DNA损伤应答途径的机制,可使我们采取相应对策选择新的抗病毒靶点,从而有利于新型抗病毒药物的开发。     

Relationships between the lucerne flea, Sminthurus viridis (L.) (Collembola: Sminthuridae), and damage to lucerne

Abstract The effect of lucerne flea, Sminthurus viridis , on plant growth (stem length and leaf number) and damage (percentage of leaves damaged and the percentage reduction in leaf area in the top, mid and lower thirds of stems) was considered at 2-weekly intervals in three consecutive lucerne growth cycles, each with a different mode of attack. The data were analysed to progressively determine relationships leading to a proposal for plant-based thresholds for lucerne flea control. Lucerne flea affected each factor measured, with damage considered more appropriate for making control decisions than plant growth. Damage increased from the base of plants upwards and its effect on yield was carried over into subsequent growth cycles. Damage was significantly related to lucerne flea numbers ( P  < 0.001) in two growth cycles and was higher when large nymphs or adults were dominant in one of these cycles. Yield was closely and best related to the percentage of the total number of leaves damaged ( R ² = 81.3%). The percentage of leaves damaged was also related to loss of final yield estimated at 2 ( R ² = 81.3%), 4 ( R ² = 78.9%) and 6 ( R ² = 66.6%) weeks into the first growth cycle only. Direct damage in the other two cycles did not result in yield loss. The percentage of leaves damaged (± confidence intervals) equating to 5% increments in yield loss were estimated at 2, 4 and 6 weeks into the first growth cycle. These are proposed as damage or treatment thresholds for testing.     

Leucocytosis as a marker of organ damage induced by chronic strenuous physical exercise

The effects of strenuous physical exercise on the serial changes in the haematological, biochemical and hormonal markers were investigated. A group of 14 soldiers, aged 24–36 years, took part in a military training course for about 13 weeks. After severe exercise stress, an increase (90%) in the number of peripheral blood leucocytes was observed. The degree of leucocytosis showed a close correlation with the values of some serum parameters, such as concentrations of aspartate aminotransferase (AST;r = 0.747), lactate dehydrogenase (LD;r = 0.748), blood urea nitrogen (r = 0.756), creatine kinase (CK;r = 0.637), manganese-superoxide dismutase (Mn-SOD;r = 0.508), alanine aminotransferase (ALT;r = 0.542) and uric acid (r = 0.538), and concentrations of urinary parameters, such as vanilmandelic acid (r = 0.429) and free cortisol (r = 0.437). The subjects showing prominent leucocytosis over 9500 cells · l^–1 exhibited a lower concentration of serum cholinesterase than those who showed milder leucocytosis. The serum Mn-SOD concentration was closely correlated with the serial changes in serum concentrations of AST, ALT, LD and CK, indicating exercise-induced muscle and liver damage. The change in peripheral leucocyte number was assumed to be diagnostically informative and may be a prognostic marker, reflecting organ damage and restoration after strenuous physical exercise.     

Impact of deer in lowland Britain on agriculture, forestry and conservation habitats

Probably in response to recent changes in habitat structure, populations of a number of species of deer are increasing both in numbers and in geographical distribution in lowland Britain. In the wake of this expansion there is increasing awareness and concern over damage to agriculture/horticulture and forestry, as well as damage to sensitive vegetation in conservation areas. Despite a perception that damage levels are rising, data that actually quantify the scale of impact by deer on lowland agriculture and forestry interests or conservation habitats are scarce. This review attempts to draw together such objective data as are available to assess more formally the actual impact of deer damage in these different contexts and the economic significance of damage caused. The review concludes with a brief consideration of implications for management. The majority of agricultural damage reported in England and Wales was due to Fallow, Red and Roe Deer; Muntjac were only implicated in a little horticultural damage where they are numerous. Most reports were of damage to pasture or cereals, with oilseed rape, nursery and orchard crops also frequently damaged. Because of fundamental differences in ecology and distribution, different species of deer were implicated in different types of damage, depending on feeding habit and distribution in relation to geographical patterns of crop-type. In a woodland context, Fallow, Red and Roe Deer were implicated in the majority of reported damage in lowland UK, which is most frequent in the north of England and lowest in Wales. Despite the apparent severity of damage caused to agriculture or forestry, the actual economic significance of such damage would appear in many cases to be negligible or small. Field crops frequently recover completely from such damage, and although woodland crops may be checked and quality of the timber may be reduced as a consequence of earlier browsing damage, losses may be far less than they first appear. This whole question of the true economic cost of deer damage needs further research. Deer damage to conservation habitats in England and Wales appears largely restricted to woodland; impact on heathlands, grasslands and wetlands is generally welcomed as helping to arrest invasion of scrub. Within woodlands, while concern is expressed in a small number of cases over losses of sensitive ground flora or suppression of natural regeneration, the major problem is in damage to coppice regrowth on sites where coppice management has been recently reintroduced.     

压力波对听觉器官的致伤作用——Ⅰ.致伤部位和损伤特性

本工作用二十余种武器压力波源在不同暴露条件下对近二千只豚鼠进行了系统的致伤实验。结果表明,压力波暴露后致伤部位主要在中耳和内耳;即使压力峰值已高达190dBSPL,听觉中枢还未见有损伤迹象。中耳损伤和内耳损伤的程度都与压力波的强度有关,但两者并不平行,压力峰值大时压力波可以只损伤或主要损伤中耳,压力峰值不很大但重复发数较多或脉宽较大时,则可能只损伤或主要损伤内耳。在一定的条件下,中耳的损伤能缓冲压力波对内耳的冲击,从而减轻内耳的损伤。在中耳损伤或中耳、内耳混合损伤时,豚鼠的听力丧失并没有象在人的噪声性耳聋时(内耳损伤为主)常见的那种突出的高频选择性。     

Uhrf2 is important for DNA damage response in vascular smooth muscle cells

Emerging evidence shows that Uhrf1 plays an important role in DNA damage response for maintaining genomic stability. Interestingly, Uhrf1 has a paralog Uhrf2 in mammals. Uhrf1 and Uhrf2 share similar domain architectures. However, the role of Uhrf2 in DNA damage response has not been studied yet. During the analysis of the expression level of Uhrf2 in different tissues, we found that Uhrf2 is highly expressed in aorta and aortic vascular smooth muscle cells. Thus, we studied the role of Uhrf2 in DNA damage response in aortic vascular smooth muscle cells. Using laser microirradiation, we found that like Uhrf1, Uhrf2 was recruited to the sites of DNA damage. We dissected the functional domains of Uhrf2 and found that the TTD, PHD and SRA domains are important for the relocation of Uhrf2 to the sites of DNA damage. Moreover, depletion of Uhrf2 suppressed DNA damage-induced H2AX phosphorylation and DNA damage repair. Taken together, our results demonstrate the function of Uhrf2 in DNA damage response.     

烤烟低温冷害指数构建及其变化特征

使用1961-2009年云南烤烟种植区62个气象代表站的逐日平均气温和最低气温,基于低温指标和权重指数构建了烤烟低温冷害指数模型,采用线性趋势及M-K突变检测方法,分析了低温冷害指数的变化特征.结果表明:1961-2009年春、夏、秋烤烟低温冷害指数全省平均值逐年变化均呈减弱趋势,春季减弱最为显著,夏秋减弱趋势不及春季且不显著;春、夏烤烟低温冷害指数全省平均值在20世纪60年代和70年代最高,在2001-2009年最低,秋季则为60年代最高,70年代最低;各季节中低温冷害指数呈减弱趋势及变化显著的站点春、夏季最多,秋季最少;M-K检测表明,春季低温冷害指数全省逐年平均值变化趋势显著,并在1997年出现突变点,而夏季和秋初变化均不显著,春季全省发生显著突变的站点达30％,但夏秋季不到10％,各站点出现突变的时间以20世纪80年代及90年代末期为主.     

Cisplatin resistance: Preclinical findings and clinical implications

Cisplatin is used for the treatment of many types of solid cancers. While testicular cancers respond remarkably well to cisplatin, the therapeutic efficacy of cisplatin for other solid cancers is limited because of intrinsic or acquired drug resistance. Our understanding about the mechanisms underlying cisplatin resistance has largely arisen from studies carried out with cancer cell lines in vitro. The process of cisplatin resistance appears to be multifactorial and includes changes in drug transport leading to decreased drug accumulation, increased drug detoxification, changes in DNA repair and damage bypass and/or alterations in the apoptotic cell death pathways. Translation of these preclinical findings to the clinic is emerging, but still scarce. The present review describes and discusses the clinical relevance of in vitro models by comparing the preclinical findings to data obtained in clinical studies.     

Identifying threshold densities for wild deer in the UK above which negative impacts may occur

• 1 At high densities, deer populations may have adverse effects upon and within their environment. In this review we explore published and unpublished information to derive density thresholds for deer species in relation to impacts upon agriculture, forestry, conservation habitats, road traffic, and human and livestock health in the UK. Impact levels are affected by many factors other than absolute density. We therefore seek to establish the range of densities within which negative impacts might start to occur and which should trigger objective monitoring of actual impacts.
• 2 In commercial forestry, a threshold of 4 deer per 100ha has been suggested. Unfenced native woodlands seem to regenerate naturally if there are fewer than 4–5 large deer or fewer than 25 roe deer Capreolus capreolus per 100ha; open habitats may suffer only light or moderate impacts from red deer Cervus elaphus at landscape densities of 7–8 per 100ha.
• 3 Woodland bird species may have declined where deer densities are high but absolute thresholds seem impossible to establish. One study suggests maximum diversity at about 8 white‐tailed deer Odocoileus virginianus per 100ha.
• 4 Deer–vehicle collisions are affected by various factors in addition to deer density, but British and American studies suggest that accident frequencies decline at densities below 7–8 per 100ha.
• 5 Fallow deer Dama dama populations may maintain bovine TB (bTB) infection at much lower densities (25/100ha) than red or roe deer (91/100ha and 200/100ha, respectively) assuming 100% prevalence. Even at 30% prevalence a density of 75 fallow deer per 100ha could maintain bTB within the population.
• 6 We conclude that deer density alone is unlikely to be a good predictor of impact, and suggest that long‐term management should be based on assessment both of actual impacts and apparent density of deer.

     

SUMO化修饰与DNA损伤修复

由于体内外因素的影响,DNA损伤是生物生命周期中的常见现象,如果得不到及时的修复,DNA损伤的积累将导致基因组的不稳定及染色质的异常,并可能导致肿瘤的发生发展。SUMO化修饰是体内一个重要的蛋白质翻译后修饰,越来越多的研究发现SUMO化修饰与多个参与DNA损伤反应、维持基因组稳定的蛋白质相关,有可能参与肿瘤的发生。本文将阐述SUMO化修饰与DNA损伤修复的关系。     

牙鲆胚胎冷冻损伤的观察

为了观察牙鲆胚胎在冷冻保存过程中的形态受损情况,将其浸入20%PM（20%丙二醇和20%甲醇1∶1的混合液）中平衡,并用程序化法和玻璃化法对其冷冻保存2h后解冻,用摄影显微镜记录其在抗冻剂里平衡时和冷冻保存后的形态。结果显示在平衡过程中胚胎卵膜出现凹陷（称为溶液损伤）,但可以恢复;在冷冻过程出现胞内冰损伤,是致命的;用程序化法冷冻保存的尾芽期胚胎卵膜和卵黄完好,胚体边缘受伤;用玻璃化法保存的尾芽期胚胎,卵膜和卵黄损伤较重,胚体损伤较轻;因此将玻璃化法和程序化法结合可以达到扬长避短的效果。     

Greenfinch feeding behaviour and impact on a rapeseed crop in Oamaru,New Zealand

Abstract

Feeding behaviour of greenfinch flocks on a rapeseed crop was both organised and coordinated. The birds caused minor damage to a large number of plants. They ate approximately half of the rapeseeds from the pods they attacked, and the remaining seeds subsequently fell to the ground. Ripe pods were preferred, and early-ripening plants sustained the heaviest damage. Seed loss calculations from transect data were unsatisfactory because of the high variability of damage levels. Maximum consumption estimates (6.8 g rapeseed per bird per day) and the feeding pressure exerted over the damage period indicated a total seed loss over 16.2 ha of 1.44 tonnes. Earlier planting of the rapeseed crop is suggested as the best method of reducing damage due to birds.     

Oxygen accelerates the accumulation of mutations during the senescence and immortalization of murine cells in culture

Oxidative damage is a causal factor in aging and cancer, but it is still not clear how DNA damage, the cellular responses to such damage and its conversion to mutations by misrepair or misreplication contribute to these processes. Using transgenic mice carrying a lacZ mutation reporter, we have previously shown that mutations increase with age in most organs and tissues in vivo . It has also been previously shown that mouse cells respond to oxidative stress, typical of standard culture conditions, by undergoing cellular senescence. To understand better the consequences of oxidative stress, we cultured mouse embryo fibroblasts (MEFs) from lacZ mice under physiological oxygen tension (3%) or the high oxygen tension (20%) associated with standard culture, and determined the frequency and spectrum of mutations. Upon primary culture, the mutation frequency was found to increase approximately three-fold relative to the embryo. The majority of mutations were genome rearrangements. Subsequent culture in 20% oxygen resulted in senescence, followed by spontaneous immortalization. Immortalization was accompanied by an additional three-fold increase in mutations, most of which were G:C to T:A transversions, a signature mutation of oxidative DNA damage. In 3% oxygen, by contrast, MEFs did not senesce and the mutation frequency and spectrum remained similar to primary cultures. These findings demonstrate for the first time the impact of oxidative stress on the genomic integrity of murine cells during senescence and immortalization.     

Measuring tolerance to herbivory: accuracy and precision of estimates made using natural versus imposed damage

Abstract.— Tolerance to herbivory (the ability of a plant to incur herbivore damage without a corresponding reduction in fitness) can be measured using either naturally occurring or imposed herbivore damage. After briefly reviewing some of the advantages and disadvantages of these approaches, we present calculations describing the degree to which estimates of tolerance will be biased by environmental variables that affect both herbivory and fitness. With naturally occurring herbivory the presence of environmental variables that are correlated with herbivory and fitness will result in biased estimates of tolerance. In contrast, estimates obtained from experiments in which herbivory is artificially imposed will be unbiased; however, under a wide range of parameter values these estimates will be less precise than estimates obtained from experiments in which herbivory is not manipulated.     

Calibration of the comet assay for the measurement of DNA damage in mammalian cells

We used X-rays from a linear accelerator and from a low energy therapeutic source to calibrate the single cell gel electrophoresis (comet assay), a widely used method to measure DNA damage. γ-Rays from ⁶⁰Co, with known efficiency in inducing DNA breakage, were used as reference. Human lymphocytes and one murine tumour cell line, F10-M3 cells, were irradiated under different experimental conditions. A similar relationship between radiation dose and induced DNA damage was obtained with γ- and X-rays. A calibration curve was constructed to convert the comet assay raw data into break frequency. The median levels of DNA breaks and oxidative damage in circulating lymphocytes from healthy volunteers were calculated to be 0.76 and 0.80 breaks/10⁹ Da, respectively, (0.50 and 0.52 breaks/10⁶ bp). The values of oxidative DNA damage were in the same order of magnitude as those found by others with HPLC methods.     

Calibration of the comet assay for the measurement of DNA damage in mammalian cells

We used X-rays from a linear accelerator and from a low energy therapeutic source to calibrate the single cell gel electrophoresis (comet assay), a widely used method to measure DNA damage. γ-Rays from ⁶⁰Co, with known efficiency in inducing DNA breakage, were used as reference. Human lymphocytes and one murine tumour cell line, F10-M3 cells, were irradiated under different experimental conditions. A similar relationship between radiation dose and induced DNA damage was obtained with γ- and X-rays. A calibration curve was constructed to convert the comet assay raw data into break frequency. The median levels of DNA breaks and oxidative damage in circulating lymphocytes from healthy volunteers were calculated to be 0.76 and 0.80 breaks/10⁹ Da, respectively, (0.50 and 0.52 breaks/10⁶ bp). The values of oxidative DNA damage were in the same order of magnitude as those found by others with HPLC methods.     

DNA Damage Checkpoint, Damage Repair, and Genome Stability

Genomic DNA is under constant attack from both endogenous and exogenous sources of DNA damaging agents. Without proper care, the ensuing DNA damages would lead to alteration of genomic structure thus affecting the faithful transmission of genetic information. During the process of evolution, organisms have acquired a series of mechanisms responding to and repairing DNA damage, thus assuring the maintenance of genome stability and faithful transmission of genetic information. DNA damage checkpoint is one such important mechanism by which, in the face of DNA damage, a cell can respond to amplified damage signals, either by actively halting the cell cycle until it ensures that critical processes such as DNA replication or mitosis are complete or by initiating apoptosis as a last resort. Over the last decade, complex hierarchical interactions between the key components like ATM/ATR in the checkpoint pathway and various other mediators, effectors including DNA damage repair proteins have begun to emerge. In the meantime, an intimate relationship between mechanisms of damage checkpoint pathway, DNA damage repair, and genome stability was also uncovered. Reviewed hereinare the recent findings on both the mechanisms of activation of checkpoint pathways and their coordination with DNA damage repair machinery as well as their effect on genomic integrity.