哺乳动物化石牙齿釉质的碳,氧同位素组成与古气候重建方面的研？…

哺乳动物化石牙齿釉质能有效地抵抗成岩作用的影响,并保存原始的碳、氧稳定同位素组成信息。通过对食草类哺乳动物化石牙齿釉质同位素组成的分析可以重建这些动物生存时代的古气候。釉质碳酸盐的碳同位素组成响应于取食植物的碳同位素组成,藉此可以恢复陆地生态系统中Ｃ３和Ｃ４植物的分布比例,这个比例主要受控于大气的ＣＯ２水平、气压和光照等因素,与不同的纬度带和气候带有关,釉质磷酸盐的氧同位素组成响应于饮用水的氧同位     

哺乳动物化石牙齿釉质的碳、氧同位素组成与古气候重建方面的研究进展

哺乳动物化石牙齿釉质能有效地抵抗成岩作用的影响,并保存原始的碳、氧稳定同位素组成信息。通过对食草类哺乳动物化石牙齿釉质同位素组成的分析可以重建这些动物生存时代的古气候。釉质碳酸盐的碳同位素组成响应于取食植物的碳同位素组成,藉此可以恢复陆地生态系统中C3和C4植物的分布比例,这个比例主要受控于大气的CO2水平、气压和光照等因素,与不同的纬度带和气候带有关;釉质磷酸盐的氧同位素组成响应于饮用水的氧同位素组成,饮用水来源于大气降水,其氧同位素组成响应于温度变化,所以釉质的氧同位素组成与气温之间有显著的线性相关,藉此可以计算地史时期的年平均温度、绘制气候的冷暖变化曲线。     

哺乳动物牙釉质碳氧稳定同位素揭示早期人类演化与环境关系

早期人类演化、扩散、技术发展与自然环境的关系一直是学术界关注的前沿与热点.本文梳理了环境变化与早期人类演化关系研究中牙釉质碳氧稳定同位素分析的研究历史、原理以及取样方法,与此同时,介绍了不同学者利用哺乳动物牙釉质碳氧稳定同位素分析在早期人类演化与环境关系探索的相关研究进展,并对东非早期人类奥杜威技术向阿舍利技术转变过程...     

巨猿牙齿釉质厚度及对食性适应与系统演化的意义

步氏巨猿(Gigantopithecus blacki)是更新世时期生活于我国华南地区的一种超大型猿类, 它的体态特征和演化分类倍受关注。牙齿釉质厚度在探讨灵长类食性、环境适应以及系统演化方面具有重要意义。本文利用显微CT技术构建18颗巨猿臼齿虚拟模型, 测量其釉质厚度。将巨猿釉质厚度与现代人、现生类人猿、古人类、中新世古猿及其他现生灵长类进行比较, 从牙齿釉质厚度探讨巨猿的食性适应和系统演化问题。结果发现巨猿的实测釉质厚度是目前所有已知现生和化石灵长类中最厚的, 只有傍人、南非早期人属及奥兰诺古猿三种化石灵长类与之接近; 如果考虑不同物种牙齿与身体大小的关联因素, 相对釉质厚度指数显示巨猿属于"厚"釉质类型, 但非"超厚"类型, 低于奥兰诺古猿、傍人、南非早期人属; 巨猿与某些中新世古猿 (如原康修尔猿尼安萨种、非洲古猿)、南方古猿、东非早期人属、亚洲直立人以及现代人、现生卷尾猴的相对釉质厚度指数相近。巨猿的厚釉质特征与其食性和环境适应密切相关, 使得牙齿具有非常强的抗磨损功能, 能够适应长时间的咀嚼和研磨食物。从釉质厚度的系统演化角度推测, 厚釉质应该是人类祖先的特征性状, 巨猿有可能是早期人类支系演化过程中的一个特化旁支, 同时也不排除巨猿是从某种具有厚釉质的中新世古猿旁支平行演化而来的可能性。     

湖泊摇蚊亚化石氧同位素:一种有效的古气候代用指标

湖泊沉积物摇蚊亚化石的氧同位素作为一种新的指标,近来成为古气候重建的一种重要手段。本文在综述摇蚊亚化石氧同位素的来源特征、迁移过程及影响因素的基础上,揭示了其在古气候重建研究中的原理、优势、应用范围,并介绍了目前存在的实验技术瓶颈(生物体内氧同位素的提取)及其进展。本文着重涉及以下内容:(1)湖泊沉积物中摇蚊亚化石相较其它微体生物指标有易保存、个体大显著优势,方便提取足量的样品进行氧同位素分析;(2)摇蚊头壳氧同位素含量的影响因素众多,室内控制实验成果表明其幼虫体内约69%的氧都来自于栖息地的水中,而与食物中的氧同位素关系不显著,因此为摇蚊头壳中氧同位素信号的解释、历史气候条件的重建提供了重要的理论依据;(3)实验分析技术定量评估了不同实验方案(如化学处理、样品量大小、锡箔容器等)的误差;同时同位素质谱仪技术的发展极大的方便了测量过程。(4)摇蚊头壳氧同位素能较好地重建历史气温及降水的情况,但目前主要研究工作在欧美高山、极地地区展开。     

苔藓植物化石的研究进展及应用

苔藓植物化石为探索植物界物种进化发展和重建古气候环境提供了重要的科学基础。该文通过大量的化石资料,结合当今前沿科学技术和热点问题,从苔藓植物起源分化及物种多样性分布、形态表现及分子进化及古气候环境的重建等方面对该领域的研究成果进行了综述和总结。(1)苔藓植物起源于早古生代的赤道低纬度区,至少在奥陶纪时期就有了苔类与藓类的分化;其物种多样性总体上呈增加趋势,并具有低纬度区物种多样性高的特点,但个别地质年代苔类与藓类的物种多样性具有明显差异,凸显了二者对气候环境的敏感程度不同。(2)苔藓植物具有缓慢的形态和分子进化,其中苔类的进化速率相对较快。(3)对于显生宙古气候环境的变迁及重建,苔藓植物化石自身的形态特征、孢粉学和古分子化石的分析、以及碳和氧同位素的测量均提供了重要的科学依据。针对苔藓植物化石研究中存在的问题,作者提出了自己的观点。     

广西化石猩猩牙齿釉质厚度研究

华南和东南亚发现大量更新世的猩猩牙齿化石。本研究应用CT扫描三维重建的技术方法研究了广西更新世化石猩猩牙齿釉质厚度,并与现生类人猿、现代人、化石类人猿以及早期人类进行比较分析。结果显示:广西猩猩同类牙齿的釉质厚度与牙齿大小相关性很小;臼齿和前臼齿釉质厚度在上下颌之间不存在显著性差异;来自广西不同地区的猩猩化石牙釉质厚度无显著差异。与早期人科成员相比,广西猩猩的牙釉质相对较薄,平均与相对釉质厚度值都明显小于南方古猿、傍人。与早期人属相比,小于直立人、尼人以及非洲和欧洲的早期人属化石。与现代人和现生灵长类相比,广西化石猩猩釉质厚度明显大于大部分猴类和非洲大猿;平均釉质厚度稍大于现生猩猩,而与现代人更为接近;相对釉质厚度小于现代人,而与现生猩猩差异不大,都属于偏厚型釉质。本文讨论了釉质厚度与系统分类演化、食性适应的相关问题,作者推测釉质厚度可能是物种的特征属性,与牙齿功能适应有密切关联。     

哺乳动物化石群落线指示的甘肃临夏盆地晚新生代环境演变(英文)

哺乳动物群的演替过程在重建古环境和古气候中具有重要的作用。群落线(cenogram)是将陆生哺乳动物群中非肉食性种类按体重分布顺序排列的一种曲线,并可在图中将肉食性种类单独排序,以便显示动物群的整体组成。通过与现生哺乳动物群的比较,化石动物群的群落线已经被用来推断古环境及其在地质历史时期的变化。基于甘肃临夏盆地晚新生代哺乳动物群的群落线进行古环境重建,时代从晚渐新世直到早更新世。大多数化石种类的体重通过下第一臼齿面积与体重的回归公式来估计,少数种类用其他牙齿或肢骨来估计。大多数体重估计的测量数据来自临夏盆地的化石,少数取自文献。对7个化石动物群分别计算群落线的统计结果,在此基础上进行古环境解释。这些分析揭示了临夏盆地在晚中新世、早上新世和早更新世具有开阔的环境,晚渐新世是半开阔的林地,而中中新世为比较紧密的森林;在晚渐新世和晚中新世早期气候干燥,晚中新世的其他时段以及早上新世和早更新世为半干旱环境,而中中新世时期相当湿润。     

扫描电镜研究牙齿釉质的制样方法

<正> 釉质是动物体内最硬的组织,它被覆于几乎所有的哺乳动物牙齿冠面,由于它的硬度很高,大大提高了牙齿对食物的粉碎和咀嚼机能.多年来,人们利用各种仪器和方法对釉质的组织学结构和化学成分作了大量的分析和研究,为探讨釉质的发育,进化以及治疗牙齿疾病等方面的应用奠定了基础.扫描电镜用于牙齿微观结构的研究,扩展了人们对釉质结构的了解,越来越多的古生物学家和口腔医学专家认为釉质在动物的分类和系统发育研究中具有重要作用.扫描电镜由于其制样方法比较简单,放大倍数高、立体感强,可以直接观察样品表面结构等优点而更适合脊椎动物化石材料的研究工作.在国外,研究现生和化石脊椎动物牙齿微观结     

新疆哈密雷兽化石的发现

1959年春,新疆维吾尔自治区地质局在哈密野马泉采到几块哺乳动物牙齿化石寄古脊椎动物与古人类研究所鉴定。这几块标本是一种副雷兽(Parabrontops)的臼齿。雷兽化石在新疆发现还是首次。     

Exercise-induced hormone responses in girls at different stages of sexual maturation

The dependence of exercise-induced hormone responses on sexual maturation was tested in a 3-year longitudinal experiment on 34 girls (aged 11–12 years at the beginning). Sexual maturation was evaluated by Tanners five-stage scale. Children cycled for 20-min at 60% maximal oxygen uptake once a year. Cortisol, insulin, growth hormone, β-oestradiol, progesterone and testosterone concentrations in venous blood were determined by radioimmunoassay procedures. Basal concentrations of growth hormone increased and of cortisol decreased when breast stage III was reached. Reaching breast stage IV was associated with an increase in basal concentrations of β-oestradiol, progesterone and testosterone. The exercise induced significant increases in concentrations of cortisol, growth hormone and β-oestradiol and a decrease in insulin concentration. At breast stage III the increase in cortisol concentration was to a lower level [467 (SEM 42) vs 567 (SEM 46)nmol · l⁻¹] and growth hormone concentration to a higher level [29.4 (SEM 0.5) vs 12.8 (SEM 0.4)ng · ml⁻¹], while the fall in insulin concentration was less pronounced [postexercise level 10.6 (SEM 0.9) vs 7.8 (SEM 0.8)mU · l⁻¹] than in stage II. The magnitude of the cortisol response was reduced in the last stage of breast development (+42.1% vs +55.5% at stage II, +66.2% at stage III, and +50.0% at stage IV). The magnitude of β-oestradiol response was the lowest in breast stage IV (+15.8%) and the highest at stage V (+41.1%). The progesterone response became significant at stage IV and testosterone response at stage V. In conclusion, we found that reaching breast stage III was associated with altered responses of cortisol, insulin and growth hormone concentrations while the responses of the sex hormone concentrations became pronounced in the last stages of sexual maturation. Accepted: 17 September 1997     

Photoprotection of phytochrome

High-fluence-rate white light is shown to retard the degradation of phytochrome in etiolated seedlings of four different species: Amaranthus caudatus, Phaseolus radiatus (mung bean), Pisum sativum (garden pea), and Avena sativa (oat). In Amaranthus, a high photon fluence rate (approx. 1000 mol · m^-2 · s^-1) preserved nearly 50% of the total phytochrome over a period of 5 h; at 3 mol · m^-2 · s^-1, less than 8% remained over the same period. Kinetics of the loss of total phytochrome could be interpreted in terms of two populations, one with rapid, and one with slow, turnover rates. A log-linear relationship between fluence rate and proportion of slowly degrading phytochrome was observed; a similar relationship between fluence rate and the amount of phytochrome remaining after a 5-h light treatment was seen. In mung bean, although two populations of differing degradation rates were not resolvable, a similar log-linear relationship between fluence rate and amount remaining after a standard light treatment was evident. Detailed kinetic analyses were not performed with peas and oats, but comparisons of low and high fluence rates demonstrated that photoprotection was similarly effective in these species. In Amaranthus, transfer from high to low fluence rate was accompanied by a rapid increase in degradation rate, indicating that the retarding effect of high-fluence-rate light is not a consequence of the disablement of the degradative machinery.Immunochemical analyses confirmed the existence of photoprotection in all four species, and allowed the extension of the observations to periods of light treatment during which substantial chlorophyll production occurred. Considerable photoprotection was observed in oat seedlings exposed to summer sunlight. These results are interpreted in terms of the accumulation under high fluence rates of photoconversion intermediates not available to the degradative machinery which is specific for the far-red-absorbing form of phytochrome.Abbreviations Pfr far-red absorbing form of phytochrome - Po amount of phytochrome measured at time zero - Pt amount of phytochrome measured at time t - Ptot total phytochrome - WL white light     

论＂医德＂的基本范畴

医德是医疗卫生领域精神文明建设的重要部分,也是调整医务人员与病人、医务人员之间以及与社会之间关系的行为准则。医德范畴是指人们对现代医务人员职业道德和医患关系的总结,它不仅概括了医生所应履行的职责义务,而且反映着一段时间内医患关系的本质。本文通过对医德范畴内,医生的权利和义务、责任和良心、功力和荣誉、审慎和保密四类问题的阐述,探讨当下医生在工作中应该保持何种心态,如何与患者进行沟通,以期更好地提供医疗服务。     

Regulation of cellular immune responses by selenium

Selenium (Se) is an essential nutritional factor that affects the development and expression of cell-mediated immune responses directed toward malignant cells. These studies have shown that dietary (2 ppm for 8 wk) or in in vitro (1×10⁻⁷ M) supplementation with Se (as sodium selenite) results in a significant enhancement of the proliferative responses of spleen lymphocytes from C57B1/6J mice in response to stimulation with mitogen or antigen. Se deficiency (0.02 ppm for 8 wk) had the opposite effect. The alterations in the ability of the cells to proliferate, which occurred in the absence of changes in the endogenous levels of interleukin-2 (II₂) or interleukin 1, were apparently related to the ability of Se to alter the kinetics of expression of high-affinity Il₂ receptors on the surface of activated lymphocytes. This resulted in an enhanced or delayed clonal expansion of the cells, and in an increased or decreased frequency of cytotoxic cells within a given cell population. The changes in tumor cytotoxicity were paralleled by changes in the amounts of lymphotoxin produced by the activated cells. Dietary Se modulations had a comparable effect on macrophage-mediated tumor cytodestruction. The results also suggested that Se exerts its effect 8–24 h after stimulation, and that it most likely affects processes in the cytoplasmic and/or nuclear compartments of activated lymphocytes.     

Responses of soil bacterial and fungal communities to reciprocal transfers of soil between adjacent coniferous forest and meadow vegetation in the Cascade Mountains of Oregon

Little information exists on the responses of soil fungal and bacterial communities in high elevation coniferous forest/open meadow ecosystems of the northwest United States of America to treatments that impact vegetation and soil conditions. An experiment was conducted in which soil cores were reciprocally transplanted between immediately adjacent forests and meadows at two high elevation (∼1,600 m) sites (Carpenter and Lookout) in the H.J. Andrews Experimental Forest located in the Cascade Mountains of Oregon. Half of the cores were placed in PVC pipe (closed) to prevent new root colonization, whereas the other cores were placed in mesh bags (open) to allow recolonization by fine roots. A duplicate set of open and closed soil cores was not transferred between sites and was incubated in place. After 2 year, soil cores were removed and changes in fungal and bacterial biomasses determined using light microscopy, and changes in microbial community composition determined by PLFA analysis, and by length heterogeneity PCR of the internal transcribed spacer region of fungal ribosomal DNA. At both sites soil microbial community structures had responded to treatments after 2 year of incubation. At Carpenter, both fungal and bacterial community structures of forest soil changed significantly in response to transfer from forest to meadow, with the shift in fungal community structure being accompanied by a significant decrease in the PLFA biomarker of fungal biomass,18:2ω6,9. At Lookout, both fungal and bacterial community structures of forest soil changed significantly in response to open versus closed core treatments, with the shift in the fungal community being accompanied by a significant decrease in the 18:2ω6,9 content of closed cores, and the shift in the bacterial community structure being accompanied by a significant increase in bacterial biomass of closed cores. At both sites, fungal community structures of meadow soils changed differently between open and closed cores in response to transfer to forest, and were accompanied by increases in the18:2ω6,9 content of open cores. Although there were no significant treatment effects on the bacterial community structure of meadow soil at either site, bacterial biomass was significantly higher in closed versus open cores regardless of transfer.     

Comparative study of major lipid constituents in human and monkey aorta

The contents of total lipids, phospholipids, cholesterol, triglyceride and free fatty acid in intima and media of thoracic and abdominal segments of aorta from normal human subjects and rhesus monkeys were determined. An increase in total lipids in intima as compared to that of media was noted in both species. A comparison of lipid contents of thoracic and abdominal segments from both species revealed that abdominal segment contained significantly greater lipid. Further, human thoracic and abdominal aortic intima and media had higher content of cholesterol as compared to that of monkey aorta. The differences in lipid profile in aorta of these two species have been highlighted to provide a clue with respect to the differences in the prevalence and morphology of atherosclerosis as seen in monkey and man.     

食用菌产业发展需要科学研究的强力支撑

我国是世界食用菌产业大国,产量占全球总产80%,拥有全球最多的食用菌基础科学和应用技术研究者,近年来在这两个领域都取得了显著成绩,但仍远远不能满足产业发展的科学需求。我国食用菌产业的发展需要科学研究的强力支持。本专刊集结了食用菌的资源与利用、遗传育种、组学分析、生理栽培、加工技术、活性成分、保健功效评价等方面的论文共计32篇。本刊论文还涉及了食用菌与病原菌的互作研究、野生菌的种类产地鉴定等方面的研究。     

关于苏北地区某三甲医院进口与国产医疗设备和耗材使用情况及反馈的研究．

目的：初步了解了进口与国产医疗设备与耗材的发展状况和使用反馈情况,并对国内医疗设备与耗材行业的发展提供合理化建议。方法：通过对苏北地区某三级甲等医院设备科工作人员、医生、护士长、患者及患者家属进行调研或访谈,并以调研和访谈的统计结果为依据得出结论并提出建议。结果：技术成熟的中小型医疗设备或耗材,从质量、价格等因素综合考虑,国内产品优于进口产品,一定程度上得到了医务人员和消费者的认可。在高端大中型医疗设备与耗材方面,进口产品具有较大的技术优势。结论：国内医疗设备生产企业应当积极开展研发工作,提高产品的技术含量与质量,巩固自身在中小型医疗设备与耗材方面的优势,并努力在高端大中型医疗设备与耗材方面取得突破。     

Electroporative deformation of salt filled lipid vesicles

Membrane electroporation, vesicle shape deformation and aggregation of small, NaCl-filled lipid vesicles (of radius a = 50 nm) in DC electric fields was characterized using conductometric and turbidimetrical data. At pulse durations t_E≤ 55 ± 5 ms the increase in the conductivity of the vesicle suspension is due to the field-induced efflux of electrolyte through membrane electropores. Membrane electroporation and Maxwell stress on the vesicle membrane lead to vesicle elongation concomitant with small volume reduction (up to 0.6% in an electric field of E = 1 MV m^–1). At t_E > 55 ± 5 ms, further increases in the conductivity and the optical density suggest electroaggregation and electrofusion of vesicles. The conductivity changes after the electric pulse termination reflect salt ion efflux through slowly resealing electropores. The analysis of the volume reduction kinetics yields the bending rigidity κ = (4.1 ± 0.3) ⋅ 10^–20 J of the vesicle membrane. If the flow of Na⁺ and Cl^– ions from the vesicle interior is treated in terms of Hagen-Poiseuille's equation, the number of permeable electropores is N = 39 per vesicle with mean pore radius r_p = 0.85 ± 0.05 nm at E = 1 MVm^–1 and t_E≤ 55 ± 5 ms. The turbidimetric and conductometric data suggest that small lipid vesicles (a ≤ 50 nm) are not associated with extensive membrane thermal undulations or superstructures. In particular with respect to membrane curvature, the vesicle results are suggestive for the design and optimization of electroporative delivery of drugs and genes to cell tissue at small field strengths (≤1 MVm^–1) and large pulse durations (≤100 ms). Received: 8 July 1997 / Accepted: 15 September 1997