Hysteresis in the response of stomatal conductance in Pinus sylvestris L needles to light: observations and a hypothesis

Abstract. The response of stomatal conductance in Pinus sylvestris L. to a sequence of progressively changed photon flux densities showed hysteresis when the direction of the sequence was reversed. Hysteresis was most evident when 1 h was allowed for stabilization at a temperature of 10°C and a leaf-air vapour pressure difference of 0.5 kPa. The hysteresis was largely eliminated by a stabilization time of 2.5 h or a temperature of 20°C. Elimination of self shading also largely eliminated the hysteresis and resulted in light saturation of stomatal conductance at about 600 μE m⁻² s⁻¹ whereas with the normal grouping of fasicles light saturation was not achieved at 1750 μE m⁻² s⁻¹ even with bilateral illumination. Hysteresis was also eliminated by reduction in the maximum attainable conductance as a result of large leaf-air vapour pressure differences (> 1.8 kPa) but reducing the ambient CO₂ concentration to the compensation concentration or below had no effect on hysteresis. In addition to the hysteresis, there was a carry-over effect of the previous treatment. When the direction of the sequence of photon flux densities was changed, stomatal conductance continued to change in the direction appropriate to the previous sequence for at least 1 h. The presence of a transportable chemical intermediate is postulated, the amount or activity of which would take some time to change after a change in photon flux density. The presence of such an intermediate could account for both the sluggishness of the stomata and the carry over effect. As a result of the sluggish behaviour and carryover, in the field stomatal conductance will tend to follow the general trend in photon flux density and will be very insensitive to short term fluctuations.     

海南一新记录科——伯乐树科

报道了海南一新记录科,即伯乐树科。这是该科在中国最南端的分布,而且是分布于热带山地雨林中。文章并对其地理分布和保护建议进行了阐述。     

Surface Temperature Distribution of a Breast With and Without Tumour

Abstract

Breast cancer is a common and dreadful disease in women. Regular screening helps in its early detection. At present the most common methods of screening are by self examination and mammography. The surface temperature distribution of the breast can also provide some information on the presence of tumour. This distribution has a relation to the size and location of tumour and can be seen using thermography, where the infrared radiation emitted from the surface of the breast is recorded and a thermal pattern obtained. Thermography is a non-invasive and an inexpensive tool which could be used for early detection. In order to simulate the surface temperature distribution, a two-dimensional model of female breast with and without a carcinoma is considered. The breast is modelled with varying layer thickness close to the actual shape and numerically solved using finite element analysis. Temperature profiles are obtained for a normal breast and for a malignant one by varying the tumour size, location and the blood flow rates. The results show that the surface temperature for a malignant breast is higher than that of a normal one. In addition the size and location of the tumour do have an effect on the surface temperature distribution. It can also be seen that tumour of different sizes placed at the same location would yield the same maximum temperature depending on the blood perfusion rate.     

低剂量胸部CT自动管电流调节技术在超重体型患者检查中的可行性研究

目的：探讨16层螺旋CT自动管电流调节技术（CAREDose4D）在超重体型患者检查中的可行性。方法：收集行胸部CT检查的超重体型患者（BMI值于24-27．9之间）100例,扫描分低剂量组（A组）和常规剂量组（B组）,其中A组扫描运用CAREDose4D技术自动调节管电流;B组扫描运用常规剂量管电流为70mAs扫描。扫描完成后记录加权CT剂量指数（CTDlvol）、有效mAs值、剂量长度乘积（DLP）,计算出有效剂量（ED）及剂量减低比值（DR）,并比较两组的剂量及图像质量。结果：与B组相比,A组常规扫描辐射剂量显著降低,差异有显著统计学意义（P〈0．01）,A组剂量减低比值（DR）降低约20．84％,而图像质量无明显下降,不影响诊断,在主动脉弓上4cm（肺尖）层面A组图像质量优于B组,差异有统计学意义（x^2=8．442,P=0．015）。结论：自动管电流调节技术既可以减少患者的辐射剂量,对待超重体型患者个体化、人性化,又不影响影像诊断,是一项有价值的检查方法。     

Variable number tandem repeats – Their emerging role in sickness and health

Understanding the mechanisms regulating tissue specific and stimulus inducible regulation is at the heart of understanding human biology and how this translates to wellbeing, the ageing process, and disease progression. Polymorphic DNA variation is superimposed as an extra layer of complexity in such processes which underpin our individuality and are the focus of personalized medicine. This review focuses on the role and action of repetitive DNA, specifically variable number tandem repeats and SINE-VNTR-Alu domains, highlighting their role in modification of gene structure and gene expression in addition to their polymorphic nature being a genetic modifier of disease risk and progression. Although the literature focuses on their role in disease, it illustrates their potential to be major contributors to normal physiological function. To date, these elements have been under-reported in genomic analysis due to the difficulties in their characterization with short read DNA sequencing methods. However, recent advances in long read sequencing methods should resolve these problems allowing for a greater understanding of their contribution to a host of genomic and functional mechanisms underlying physiology and disease.     

通用流感疫苗研究进展

流感是一种对人类危害极大的传染病,接种疫苗被认为是预防流感的最有效手段。目前所用的流感疫苗主要是根据现行流行株的减毒或灭活病毒疫苗及基于流感血凝素和神经氨酸酶设计的重组蛋白质疫苗。但流感病毒变异大,易逃逸机体免疫监视,有效的疫苗须不断分离新流行株和不断更新疫苗免疫原。为解决这一问题,很多科学家一直在研究基于病毒高度保守性蛋白质、能够预防所有流感病毒毒株、可诱导持久保护性免疫的通用流感疫苗。我们对基于基质蛋白M2、核蛋白等的通用流感疫苗做一简要综述。     

声触诊组织定量技术鉴别诊断甲状腺微小癌的价值

目的：声触诊组织定量技术（VTQ）是一种新的弹性成像方法,能够定量、无创地评价组织硬度信息。本文的研究目的是探讨声触诊组织定量技术在鉴别诊断甲状腺微小癌（TMCs）中的应用价值。方法：应用VTQ 技术对110 例共114 个结节（最大直径≤1 cm）进行检测,获取并分析结节及周边甲状腺组织的横向剪切波速度（SWV）。利用ROC曲线对测量结果进行分析,评价VTQ技术的诊断价值并确定最佳诊断界值。结果：114 个结节中良性结节32 个（30 个为结节性甲状腺肿,2 个为腺瘤）,恶性结节82 个（均为乳头状癌）。甲状腺良性结节及周边甲状腺组织的SWV 平均值分别为（2.30± 0.49） m/s、（2.08± 0.40） m/s,恶性结节及周边甲状腺组织的SWV 平均值分别为（3.12± 0.97） m/s、（2.06± 0.46） m/s。恶性结节的SWV 值明显高于良性结节,两者之间差异具有统计学意义（t=5.911,P＜0.0001）;恶性结节与其周边甲状腺组织比较有显著差异（P＜0.0001）;而良性结节与其周边甲状腺组织无统计学差异（P＞0.05）。ROC曲线下面积为0.833,以2.30 m/s诊断界值点时,敏感度、特异度分别为90.2%、62.5%。结论：甲状腺恶性结节的SWV 值明显高于良性结节。VTQ 技术能够提供组织硬度信息,在鉴别诊断甲状腺微小癌方面具有一定的临床应用价值。     

圈养大熊猫性情、饲养管理和社群-性行为的关系

以往研究表明,许多成年雄性大熊猫在圈养状态下不能表达正常的社群性行为。我们设计了一个实验来研究大熊猫正常社群性行为与性情特征、展示、以及饲养管理的关系。通过调查获得大熊猫展示和饲养管理的数据,询问饲养员得知2001年繁殖季节中大熊猫的社群性行为发生频次,然后评估社群性行为能力。研究对象是分布在中国4个繁育中心的37头(12头雄性和25头雌性)成体大熊猫。通过提供新物品和气味来评估大熊猫情绪反应状况。情绪反应分为3类:畏惧、访问和访问玩耍。在有饲养员陪同玩耍的一组里,雌、雄大熊猫的"访问玩耍"的分值都较高。"畏惧"类的雌性大熊猫气味标记行为少,表达的性行为也少,并且更多地攻击接近它们的雄性,或者不理睬雄性。在繁殖季节前就接近雄性大熊猫围栏的雌性,表现出更多的气味标记行为和性行为。这些雌性的"访问玩耍"分值也高。"访问"分值高的雄性大熊猫,接近雌性的行为更多。那些与饲养员接触时间少的雄性大熊猫倾向于攻击雌性,与那些攻击性小的雄性相比,这些雄性倾向于能够接受丰富性低的环境。这些结果表明,应该采取措施减少大熊猫的畏惧,在大熊猫和饲养员之间建立积极的关系,在繁殖季节之前,增加雌性和雄性之间的熟悉程度。     

The Somatic Function of the Germ Nucleus in Pseudourostyla cris tat a: Asexual Reproduction and Stomatogenesis

The micronuclei of the ciliated protozoan Pseudourostyla cristata were eliminated by amputation shortly before binary fusion. The amicronucleate cell lines derived from regenerants were maintained for more than a year. They exhibited a lower viability and reduced vigor in asexual propagation. There was some improvement in the growth of the cell lines 1 mo after operation, but the growth rate remained subnormal even up to 1 yr of culture. The exact cause of the poor growth and survival in the first 3 wk after operation, whether the loss of the micronucleus or operational damage, remains to be determined. It is nevertheless clear that the micronucleus is important for subsequent asexual propagation. The amicronucleate cell lines were permanently crippled in morphogenesis, unlike the situation in Paramecium amicronucleates in which stomatogenesis returned to near-normal during asexual propagation. They always included some cells with a characteristically defective adoral zone of membranelles, reduced number of frontal-ventral-transverse cirri, and reduced body length. They were also reluctant to encyst. It is evident that the micronucleus is important for maintaining normality of the oral apparatus. It is postulated that the permanent stomatogenic crippling of amicronucleates might be related to genomic reduction in the developing macronucleus in sexual reproduction, as exhibited by other hypotrichs. The morphological defects associated with the adoral zone of membranelles may be rationalized as arising from the spreading of a zone of degeneration in the cortex affecting the left edge of the membranelles.     

黑色素瘤相关抗原MAAT1p15与LRP6的相互作用及其对Wnt信号通路的调控

为了深入研究Wnt信号的传导机制 ,利用GAL4酵母双杂交系统 ,以Wnt受体LRP6的胞内区为诱饵蛋白 ,筛选小鼠 11 5d胚胎cDNA文库 ,发现了一个新的LRP6相互作用蛋白 :黑色素瘤相关抗原MAAT1p15 (melanoma associatedantigenrecognizedbycytotoxicTlymphocytesp15 ) .免疫共沉淀方法证明了LRP6胞内区和MAAT1p15在哺乳动物细胞中也存在相互作用 .荧光素酶报告系统分析实验显示 ,MAAT1p15能够明显增强Wnt1和LRP6响应的下游基因的转录活性 ,提示MAAT1p15可能是LRP6的一个辅助蛋白