Assessment of a model for intron RNA secondary structure relevant to RNA self-splicing--a review

A widespread class of introns is characterized by a particular RNA secondary structure, based upon four conserved nucleotide sequences. Among such "class I" introns are found the majority of introns in fungal mitochondrial genes and the self-splicing intron of the large ribosomal RNA of several species of Tetrahymena. A model of the RNA secondary structure, which must underlie the self-splicing activity, is here evaluated in the light of data on 16 further introns. The main body or "core structure" of the intron always consists of the base-paired regions P3 to P9 with the associated single-stranded loops, with P2 present also in most cases. Two minority sub-classes of core structure occur, one of which is typical of introns in fungal ribosomal RNA. Introns in which the core structure is close to the 5' splice site all have an internal guide sequence (IGS) which can pair with exon sequences adjacent to the 5' and 3' splice sites to align them precisely, as proposed by Davies et al. [Nature 300 (1982) 719-724]. In these cases, the internal guide model allows us to predict correctly the exact location of splice sites. All other introns probably use other mechanisms of alignment. This analysis provides strong support for the RNA splicing model which we have developed.     

Phase-dependent nucleotide substitution in protein-coding sequences

It is well known that due to the degeneracy of genetic code, most of the silent substitutions appear in the third codon position, so the mutation frequency of the third codon position is much higher than that of the first two positions. However, it remains unknown whether the directionality of point mutation in three codon positions is similar or not. In this paper, through analyzing 15 sets of orthologous genes, it is revealed that most of the substitution types are significantly different between any two codon positions, especially between the 2nd and the 3rd phases. Furthermore, the average frequencies of each type of substitution calculated from the fifteen sets of orthologous genes are similar to those identified in single nucleotide polymorphisms (SNPs) of human and mouse genome. The present analyses suggest that the nucleotide substitution in protein-coding sequences is not only context-dependent (so called neighboring-nucleotide effects), but also phase-dependent, which is of significance to improving the prevalent nucleotide-evolution models.     

优秀赛艇运动员不同部位肌肉微循环血流灌注量的变化特点

目的：探讨优秀赛艇运动员不同部位肌肉微循环血流灌注量（MB）的变化特点,为无创微循环相关指标更好的应用于运动员机能监控提供参考和借鉴。方法：运用PeriFlux System5000系列激光多普勒血流仪对12名优秀男子赛艇运动员不同部位肌肉微循环血流灌注量进行无创测试,测试环境为室内,温度（25±3）℃,湿度45．O％～65．O％。结果：①基础值：肱二头肌〉肱桡肌〉股四头肌〉腓肠肌,且肱二头肌显著高于肱桡肌（P〈0．05）,极显著高于股四头肌和腓肠肌（P〈0．01）;②加热后值及加热前后差值：肱桡肌〉肱二头肌〉股四头肌〉腓肠肌,且肱二头肌、肱桡肌显著高于腓肠肌（P〈0．05）。结论：优秀男子赛艇运动员上肢肌肉值MBF值要明显高于下肢肌肉,尤其加热后值上肢肌肉明显高于下肢肌,而上肢肌肉或下肢肌肉之间则不存在明显差异,因此为了使监测结果更具有代表性,赛艇运动员进行微循环血流灌注量及其相关指标监测时应选取上肢相同肌肉上同一空间的解剖位点。     

Fluorescence and reflectance characteristics of manganese deficient soybean leaves: Effects of leaf age and choice of leaflet

Leaf reflectance and fluorescence characteristics of soybean (Glycine max cv Bragg) are influenced strongly by Mn availability. This report evaluates the effects of leaflet choice, leaf age, and leaf nodal position on several spectral characteristics. Leaves were obtained from soybeans grown hydroponically under controlled environmental conditions with wide differences in Mn supply. The ratio of constant yield fluorescence (F_o) to variable yield fluorescence (F_v), the ratios of reflectance at 750 nm to 550 nm and that at 650 nm to 550 nm, the position of the "red edge" near 700 nm, and an index of leaf "yellowness" were measured periodically. Increasing leaf age caused increases in the "red edge" and in both reflectance ratios. Leaf "yellowness" and the fluorescence ratio F_o/F_v decreased with leaf age and increased with leaf nodal position, primarily in Mn deficient leaves. Effects arising from leaf choice were smaller than those caused by Mn deficiency.     

Waterstriders (Gerris paludum F.) compensate for drift with a discontinuously working visual position servo

Waterstriders on ponds and creeks compensate for displacement caused by wind or water current with periodical jumps against the direction of drift. This behavior is mediated by visual stimuli.

菊小长管蚜的实验种群生命表

用叶子圆片法饲养菊小长管蚜,组建了既考虑若蚜个体间不同发育速率又包括成蚜翅型差异的实验种群生命表。结果表明,这一方法不但清楚地揭示了蚜虫个体发育进度差异对种群生长的影响,而且还阐明了翅二型性对种群发展的重要作用。     

On the systematic position of the family Gyrinidae (Coleoptera: Adephaga)

Various characters of adult and larval members of Adephaga and Cupedidae were analyzed, and suggest that Gyrinidae are the sister-group of the remaining Adephaga, and are not closely related to the remaining aquatic Adephaga. The aquatic families Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae seem to form a well founded monophyletic unit. The following characters are considered as synapomorphies of Adephaga excluding Gyrinidae: bifurcate condition of the muscle (= M.) tentoriopraementalis inferior, reduction of hypopharynx, strongly developed prosternal process, reduction in size and specialized modification of the ventral sclerite of the mesothorax, strongly developed mesofurcal arms, a high mesopleural ridge, globular mesocoxae restricted to rotatory movements, invaginated sternum VIII (coxostemum), the strongly curved base of the median lobe of the aedeagus, which articulates with the parameres, the rotated position of the aedeagus in repose, fusion of the larval clypeolabrum with the frons and reduction of the larval lacinia. Mesal shifting of M. episterno-coxalis prothoracis, and the fusion of the apical portions of the malpighian tubules of either side are considered as synapomorphies of Adephaga excluding Rhysodidae and Gyrinidae. Lateral reduction of the meta “sternal” transverse ridge and the presence of the subcubital setal binding patch of the hind wing are considered as synapomorphic characters of Trachypachidae, Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae. We postulate that the metacoxal fusion occurred independently in gyrmids and the common ancestor of Trachypachidae, Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae. Consequently we consider this character state as another synapomorphy of Trachypachidae and Hydradephaga excluding Haliplidae and Gyrinidae. The following characters are considered as synapomorphies of Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae: Loss of tactile setae on the head capsule, metafurcal origin on the intercoxal wall, expansion of the intercoxal wall, elongation of the subcubital setal binding patch, loss of Mm. furca-coxale anterior and posterior, reduction of the larval abdominal segments IX and X, and the shifting of the uropmphi onto the ventral side of segment VIII. Presence of M. tentorio-mandibularis and M. stipitopalpalis intemus are certainly primitive features of adult gyrinids but the distribution of these character states among most members of Adephaga is yet unclear. Chemical defence gland constituents point towards a very isolated position of Gyrinidae. The old age of the group, documented by a larva found in upper Permian deposits, may support the hypothesis of a sister-group relation-ship between Gyrinidae and the remainder of Adephaga.     

Feeding Position of Laccifer lucca on Dalbergia balansae and the Influence of Parasitism on Bark Structure

When Laccifer lacca fed in the bark of Dalbergia balansae, the penetration in the bark by a stylet was mainly intracellular, seldom intercellular. Finally, the stylet arrived at the funtional sieve element, and fed in it. The tip of tt,e stylet was at a distance of 0.48–0.78 mm from the surface of periderm. 70.3% of the stylets fed in the zone of newly-differentiated sieve elements. The fed sieve element had P-protein and callose, and exhibited no serious reaction of injury. The parenchyma cells that were pierced through by the stylet and the neighbouring cells Lad obvious reaction of injury, such as: thickened cytoplasm and plasmolysed; dark stained nuclei; smaller starch grains and intracellular deposition of concentrated golden material. The stylet that pierced through the bark was encircled by a stylet sheath consisted of proteins. The stylet sheath looked like a string of beads as a whole. Branching stylet sheath was observed. Some branches even reached far into the xylem, but the stylet finally reached the sieve element. At the same time, the stylet might penetrate through many sieve elements, finally reach newly-differentiated sieve elements. These results suggest that feeding of Laccifer lacca was a process of initiative choice. Two years after collecting shellac by means of skinning instead of cutting the branch, tb.e stylets and styler sheaths still remained in the bark. Several layers of ceils around them were dead and fully imbued with yellow-brown material. Stylers and styler sheaths in the outer cortex were surrounded by bending phellogen and separated from the living cells, forming many cyst-like structures in the periderm. Such bark should not be further used for feeding.     

自由体位分娩加分娩减痛法在初产顺产妇中的临床应用效果

目的:研究和探讨自由体位分娩法和分娩减痛法结合起来在初产顺产妇中的临床应用效果。方法:选取2013年1月至2013年12月已被收治的符合标准的初产顺产妇女360例为研究对象,将其随机分成A1组(自由体位分娩法组)、A2组(分娩减痛法组)和A1+A2组(两种方法结合组),每组120例。观察和比较三组产妇阴道分娩产程时间、疼痛等级评分、出血量、剖宫产率、新生儿Apgar评分情况和产后不良情况发生率。结果:①A1+A2组的分娩产程时间低于A1组及A2组,疼痛等级评分优于A1组和A2组(P均0.05);②A1+A2组的分娩过程中的出血量和剖宫产率均低于A1组及A2组(P0.05);③A1+A2组新生儿Apgar评分情况比A1组及A2组好(P0.05);④A1+A2组产后不良情况的发生率也低(P0.05)。然而以上观察指标A1组与A2组之间的差异均无统计学意义(P0.05)。结论:在临床实践过程中对初产顺产产妇实施自由体位分娩结合分娩减痛法可以显著地改善产妇分娩过程中的不良情况,对新生儿的影响也是积极的。两种方法的综合应用更具有良好的临床效果。