基因网络相继故障机理分析

癌相关基因在疾病发生与发展过程中的作用机理是非常重要的研究课题。现代数据分析方法,为从基因组数据中推断癌相关基因之间的关联,以及分析基因组的作用机理提供了有效的手段。本文根据基因表达谱数据分别建立了正常组织与神经胶质瘤和肾癌的患病组织的基因互信息网络。用以介数为基础的相继故障模型研究了基因网络结构与鲁棒性之间的关系。定义了网络相继故障节点百分比、平均相继故障规模和相继故障规模比例累积概率等衡量网络鲁棒性的结构参数。通过对照组与实验组之间的比对,我们发现实验组网络比对照组网络更加稳定,并将引起网络大规模相继故障的基因称为结构性关键基因。这些结构性关键基因中的一部分已经被证明与神经胶质瘤或肾癌的发生、发展有密切关系。大多数基因被预测在神经胶质瘤和肾癌的发生中起着激励或抑制作用,需要进一步的试验验证。预测信息为研究癌相关基因提供了新的方向。     

越南苦苣苔科石蝴蝶属植物随记暨国家级分布新记录

石蝴蝶属(Petrocosmea Oliv.)植物的现代分布与分化中心位于中国的西南山地以及周边国家和地区,如印度(阿萨姆邦)、缅甸、泰国、越南等也有分布。近年来,中国和中南半岛上各个国家和地区的新分类群和国家级新记录层出不穷,进一步加深了研究人员对中国和中南半岛植物区系以及该属植物在上述区域的多样性的理解。例如,滇黔石蝴蝶[Petrocosmea martinii (H. Léveillé)H. Léveillé]和丝毛石蝴蝶(P. sericea C.Y. Wu ex H. W. Li)曾被认为是中国的特有种,前者分布于贵州、广西北部和云南东南部,而后者仅见于云南东南部。该文报道了这两种石蝴蝶属植物的越南国家级分布新记录。这两个新记录种的发现,使得越南分布的石蝴蝶属植物种的数量上升到了5 种,这些新记录种的报道或暗示未来在与中国西南山地邻近的地区还将会有更多该属的新分类群或新记录有待发现。该文还同时提供了这两个国家级分布新记录物种的描述、图示、濒危等级现状评价以及目前所有越南已知分布的石蝴蝶属植物的检索表以备检索和核对。     

A new trogiid genus from lower Eocene Fushun amber (Insecta: Psocodea: Trogiomorpha)

A new fossil brachypterous psocid tax on belonging to the family Trogiidae is characterized, illustrated and described from the early Eocene Fushun amber. Paralepinotus fushunensis nov. gen., nov. sp., shares several characters with the genus Lepinotus von Heyden, 1850, but differs from it mainly by the presence of tibial spurs other than apical ones and the absence of a forked sensillum on the last maxillary palp. This fossil taxon is also characterized by relatively developed elytriform forewing but still not reaching the tip of the abdomen. A checklist of all known Trogiidae is provided.     

Evidence for Chromosomal Macronuclear Substructures in Tetrahymena*†

SYNOPSIS.
Under the growth conditions employed, the G₁ macronucleus of Tetrahymena pyriformis HSM contains 7.4 × 10^-12 g DNA, the G₂ micronucleus 0.42 × 10^-12 g. DNA content from the Tetrahymena thermophila macronucleus did not significantly differ from that of HSM, but the micronucleus contained about twice as much DNA as the micronucleus of the HSM cells. The T. thermophila macronucleus contained on average enough DNA for ˜ 35 haploid micronuclear copies. A new spreading technic allowed separation of macronuclear substructures from cells of late G₂ to early G₁. Photometric determination of DNA content of 345 individual structures suggested the existence of 5 different-sized macronuclear structures with a DNA content corresponding to 2, 4, 8, and 16 × the basic values. Comparison of the DNA content of these structures with (a) mitotic micronuclear chromosomes and (b) meiotic micronuclear chromosomes of T. thermophila cells suggests that the 5 basic values of macronuclear structures derive from structures of micronuclear chromosomes. The micronuclear chromosomes of T. pyriformis may be oligotenic. It is suggested that these results further our understanding of macronuclear organization.     

Seed Size,Seed Germination,and Seedling Survival of Brazilian Tropical Tree Species Differing in Successional Status1

Seed germination and seedling establishment patterns have been used to classify species as shade tolerant or intolerant. The main objective of this research was to investigate, under controlled conditions, seed germination of species from different successional positions as well as to follow seed germination and seedling survival under natural shade in the field. The species studied were Solarium granuloso‐leprosum, Trema micrantha, Cecropia pachystachya, Croton piptocalyx, Bauhinia forficata subsp. pruinosa. Senna macranthera, Schizolobium parahyba, Piptadenia gonoacantha, Chorisia speciosa, Pseudobombax grandiflorum, Ficus guaranitica, Esenbeckia leiocarpa, Pachystroma longifolium, Myroxylon peruiferum, and Hymenaea courbaril. Field trials were carried out at Santa Genebra Municipal Reserve, Campinas, SP, Brazil, at the forest edge and in the understory. No significant correlations were detected between successional status and seed size or seed water content. Light‐regulated germination was present only in small‐seeded species. In field experiments, most species, including the light‐sensitive ones, were able to germinate under the canopy, where a low red/far‐red ratio predominates. Most species, mainly those of early‐ and intermediate successional positions, presented low seedling survival rates under shade. Myroxylon peruiferum was the most shade tolerant species, while 5. granuloso‐leprosum, C. speciosa, P. gonoacantha, F. guaranitica, T. micrantha, and 5. parahyba were the most shade intolerant. These latter species showed little or no survival under the shade conditions.     

Ca2+-binding Motif of βγ-Crystallins

βγ-Crystallin-type double clamp (N/D)(N/D)XX(S/T)S motif is an established but sparsely investigated motif for Ca²⁺ binding. A βγ-crystallin domain is formed of two Greek key motifs, accommodating two Ca²⁺-binding sites. βγ-Crystallins make a separate class of Ca²⁺-binding proteins (CaBP), apparently a major group of CaBP in bacteria. Paralleling the diversity in βγ-crystallin domains, these motifs also show great diversity, both in structure and in function. Although the expression of some of them has been associated with stress, virulence, and adhesion, the functional implications of Ca²⁺ binding to βγ-crystallins in mediating biological processes are yet to be elucidated.     

31P nuclear magnetic resonance study on changes in phosphocreatine and the intracellular pH in rat skeletal muscle during exercise at various inspired oxygen contents

We measured ATP, phosphocreatine (PCr), inorganic phosphate (P_i), and the intracellular pH in rat hindlimb muscles during submaximal isometric exercise with various O₂ deliveries using³¹P nuclear magnetic resonance spectroscopy (³¹P NMR) to evaluate changes in energy metabolism in relation to O₂ availability. Delivery of O₂ to muscles was altered by controlling the fractional concentration of inspired oxygen (F _IO₂) at 0.50, 0.28, 0.21, 0.11 and 0.08 with monitoring partial pressure of oxygen and carbon dioxide, and bicarbonate at the femoral artery. The steady-state ratio of PCr : (PCr + P_i) during exercise decreased as a function ofF _IO₂ even at 0.21. Significant acidification of the intracellular pH during exercise occurred at 0.08F _IO₂. Change in the PCr : (PCr + P_i) ratio demonstrated that the oxidative capacity, i.e. the maximal rate of the oxidative phosphorylation reaction, in muscle was not limited by O₂ delivery at 0.50F _IO₂, but was significantly limited at 0.21F _IO₂ or below. Change in the intracellular pH at 0.08F _IO₂ could be interpreted as an increase in lactate, suggesting activation of glycolysis. Correlation between the PCr : (PCr + P_i) ratio and the intracellular pH revealed the existence of a critical PCr : (PCr + P_i) ratio and pH for glycolysis activation at around 0.4 and 6.7, respectively.     

Forest history and the development of old‐growth characteristics in fragmented boreal forests

Questions: Can small and isolated high‐conservation value forests (e.g. designated woodland key habitats) maintain old‐growth forest characteristics and functionality in fragmented landscapes? To what extent have past disturbances (natural and anthropogenic) influenced the development of old‐growth characteristics of these forests? How long does it take for selectively cut stands to attain conditions resembling old‐growth forests? Location: Southern boreal zone of central Sweden. Methods: We linked multiple lines of evidence from historical records, biological archives, and analyses of current forest structure to reconstruct the forest history of a boreal landscape, with special emphasis on six remaining core localities of high‐conservation value forest stands. Results: Our reconstructions revealed that several of these stands experienced wildfires up to the 1890s; all had been selectively harvested in the late 1800s; and all underwent substantial structural and compositional reorganization over the following 100‐150 years. This time interval was sufficient to recover considerable amounts of standing and downed dead wood (mean 60.3 m³ ha^?1), a range of tree ages and sizes (mean basal area 32.6 m² ha^?1), and dominance of shade‐tolerant spruce. It was insufficient to obtain clearly uneven tree age structures and large (>45 cm diameter) living and dead trees. Thus, these forests contain some, but not all, important compositional and structural attributes of old‐growth forests, their abundance being dependent on the timing and magnitude of past natural and anthropogenic disturbances. Our landscape‐level analysis showed marked compositional and structural differences between the historical forest landscape and the present landscape, with the latter having a greater proportion of young forests, introduction of non‐native species, and lack of large trees and dead wood. Conclusions: The remnant high‐conservation value stands were not true representatives of the pre‐industrial forests, but represent the last vestige of forests that have regenerated naturally and maintained a continuous tree cover. These traits, coupled with their capacity for old‐growth recovery, make them valuable focal areas for conservation.     

Four Species of Theridiid Spider (Araneae) from Korea with a Description of New Species, Robertus naejangensis

Four species of the family Theridiidae, Robertus naejangensis sp. nov., Chrysso pulcherrima (Mello‐Leitao), Neottiura herbigrada (Simon) and Theridion longipalpum Zhu, are described with illustrations of their diagnostic features. The latter three species are newly recorded in the Korean spider fauna.