Genetic differentiation in the winter pine processionary moth (Thaumetopoea pityocampa--wilkinsoni complex), inferred by AFLP and mitochondrial DNA markers

The winter pine processionary moth has become an important pine pest in the last century, as a consequence of the spread of pine cultivation in the Mediterranean region. The pattern of genetic differentiation of this group, that includes two sibling species (Thaumetopoea pityocampa and Th. wilkinsoni), has been studied in nine populations using amplified fragment length polymorphism (AFLP) and single strand conformation polymorphism-sequence analysis (SSCP) of the mitochondrial cytochrome oxidase 1 (COI) and cytochrome oxydase 2 (COII). Results indicate the existence of strong genetic differentiation between the two species that became separated before the Quaternary ice ages. Moreover data indicate that Th. pityocampa has a strong geographical structure, particularly evident at the nuclear level, where all pairwise phiST resulted to be highly significant and individuals from the same population resulted to be strongly clustered when an individual tree was reconstructed. The estimates of the absolute number of migrants between populations (Nm), obtained from mitochondrial and nuclear DNA markers, suggest that gene flow is low and that a gender-related dispersal could occur in this species. The males appear to disperse more than females, contributing to the genetic diversity of populations on a relatively wide range, reducing the risks of inbreeding and the genetic loss associated with bottlenecks occurring in isolated populations.     

绵刺属的分布区及其区系地理成分

绘制了绵刺属新的分布区图。阐明了该属的生态地理分布的基本特征和规律。确定了其区系地理成分为“阿拉善-东戈壁”成分。     

电刺激下丘脑外侧区对大鼠胃缺血-再灌注损伤的影响

采用夹闭大鼠腹腔动脉30min,松开动脉夹血流复灌60min的胃缺血－再灌注损伤(gastric ischemia reperfusion injury,GI-RI)模型,用电和化学刺激,电损毁的方法观察了下丘脑外侧区（lateral hypothalamic area,LHA)对GI－RI的影响,并对其机制进行了初步分析,结果表明：（1）以0．2,0．4,0．6mA的电流强度刺激LHA,GI－RI均显著加重,且有强度－效应依赖关系,LHA内注射L－谷氨酸（L－Glu)后,对LI－RI的效应与电刺激相似,电损毁双侧LHA,GI－RI面积较电刺激组明显减小;（2）损毁双侧背侧迷走复合体（dorsal vagal complex,DVC)或切损毁是LHA,GI－RI面积较电刺激组明显减小;（2）损 侧背侧迷走复合体（dorsal vagal complex,DVC)或切断膈下迷走神经均能取消电刺激LHA加重GI－RI的作用。（3）电刺激LHA使缺血－再灌注（ischemia-reperfusion,I-R)的胃粘膜丙二醛（MDA）含量升高,超氧化物歧化酶（SOD）活性降低;（4）电刺激LHA使I－R的胃液量和总酸排出量增多,而酸度,胃蛋白酶活性和胃壁结合粘液量等无明显改变,结果提示;LHA是对GI－RI具有加重作用的中枢部位,其作用是通过DVC及迷走神经下传的,电刺激LHA加重GI－RI的作用与胃粘膜MDA含量增加,SOD活性降低,胃液量和总酸排出量增加等因素有关,而似与酸度,胃蛋白酶活性,胃壁结合粘液量等因素无关。     

Origins of protein denatured state compactness and hydrophobic clustering in aqueous urea: inferences from nonpolar potentials of mean force

Free energies of pairwise hydrophobic association are simulated in aqueous solutions of urea at concentrations ranging from 0-8 M. Consistent with the expectation that hydrophobic interactions are weakened by urea, the association of relatively large nonpolar solutes is destabilized by urea. However, the association of two small methane-sized nonpolar solutes in water has the opposite tendency of being slightly strengthened by the addition of urea. Such size effects and the dependence of urea-induced stability changes on the configuration of nonpolar solutes are not predicted by solvent accessible surface area approaches based on energetic parameters derived from bulk-phase solubilities of model compounds. Thus, to understand hydrophobic interactions in proteins, it is not sufficient to rely solely on transfer experiment data that effectively characterize a single nonpolar solute in an aqueous environment but not the solvent-mediated interactions among two or more nonpolar solutes. We find that the m-values for the rate of change of two-methane association free energy with respect to urea concentration is a dramatically nonmonotonic function of the spatial separation between the two methanes, with a distance-dependent profile similar to the corresponding two-methane heat capacity of association in pure water. Our results rationalize the persistence of residual hydrophobic contacts in some proteins at high urea concentrations and explain why the heat capacity signature (DeltaC(P)) of a compact denatured state can be similar to DeltaC(P) values calculated by assuming an open random-coil-like unfolded state.     

Powder properties and their influence on dry powder inhaler delivery of an antitubercular drug

The purpose of this study was to determine if aerosol delivery of drug loaded microparticles to lungs infected withMycobacterium tuberculosis may be achieved by predicting dispersion of dry powders through knowledge of particle surface properties. Particle sizes of rifampicin-loaded poly(lactide-co-glycolide) microparticles (R-PLGA), rifampicin alone, and lactose and maltodextrin carrier particles (bulk and 75-125-μm sieved fractions) were determined by electron microscopy for the projected area diameter (D_p) and laser diffraction for the volume diameter (D_v). Surface energies (Y) of R-PLGA, rifampicin alone, lactose, and maltodextrin were obtained by inverse phase gas chromatography, surface areas (S_a) by N₂ adsorption, and cohesive energy densities by calculation. Particle dispersion was evaluated (Andersen nonviable impactor) for 10% blends of R-PLGA and rifampicin alone with bulk and sieved fractions of the carriers. D_p for R-PLGA and rifampicin alone was 3.02 and 2.83 μm, respectively. D_v was 13±1 and 2±1 μm for R-PLGA and rifampicin alone, respectively, indicating that R-PLGA was more aggregated. This was evident in Y of 35±1 and 19±6 mJ/m² for R-PLGA and rifampicin alone. D_p for lactose and maltodextrin (sieved and bulk) was approximately 40 mm. Bulk maltodextrin (D_v=119±6 mm) was more aggregated than bulk lactose (D_v=54±2 mm). This was a result of the higher S_a for maltodextrin (0.54 m²/g) than for lactose (0.21 m²/g). The Y of bulk lactose and maltodextrin was 40±4 and 60±6 mJ/m² and of sieved lactose and maltodextrin was 39±1 and 50±1 mJ/m². Impaction studies yielded higher fine particle fractions of R-PLGA from sieved lactose, 13%±3%, than from sieved maltodextrin, 7%±1%, at 90 L/min. An expression, based on these data, is proposed as a predictor of drug dispersion from carrier particles. Delivery of dry powder formulations can be achieved by characterizing particle surfaces and predicting impact on dispersion.     

Secondary cell wall deposition causes radial growth of fibre cells in the maturation zone of elongating tall fescue leaf blades

A gradient of development consisting of successive zones of cell division, cell elongation and cell maturation occurs along the longitudinal axis of elongating leaf blades of tall fescue (Festuca arundinacea Schreb.), a C3 grass. An increase in specific leaf weight (SLW; dry weight per unit leaf area) in the maturation region has been hypothesized to result from deposition of secondary cell walls in structural tissues. Our objective was to measure the transverse cell wall area (CWA) associated with the increase in SLW, which occurs following the cessation of leaf blade elongation at about 25 mm distal to the ligule. Digital image analysis of transverse sections at 5, 15, 45, 75 and 105 mm distal to the ligule was used to determine cell number, cell area and protoplast area of structural tissues, namely fibre bundles, mestome sheaths and xylem vessel elements, along the developmental gradient. Cell diameter, protoplast diameter and area, and cell wall thickness and area of fibre bundle cells were calculated from these data. CWA of structural tissues increased in sections up to 75 mm distal to the ligule, confirming the role of cell wall deposition in the increase in SLW (r2 = 0.924; P < or = 0.01). However, protoplast diameter of fibre cells did not decrease significantly as CWA increased, although mean thickness of fibre cell walls increased by 95 % between 15 and 105 mm distal to the ligule. Therefore, secondary cell wall deposition in fibre bundles of tall fescue leaf blades resulted in continued radial expansion of fibre cells rather than in a decrease in protoplast diameter.     

Tillering in grain sorghum over a wide range of population densities: identification of a common hierarchy for tiller emergence,leaf area development and fertility

Most studies of tiller development have not related the physiological and morphological features of each culm to its subsequent fertility. This introduces problems when trying to account for the effects of tillering on yield in crop models. The objective of this study was to detect the most likely early determinants of tiller fertility in sorghum by identifying hierarchies for emergence, fertility and grain number of tillers over a wide range of assimilate availabilities. Emergence, phenology, leaf area development and dry weight partitioning were quantified weekly for individual tillers and main culms of tillering and uniculm plants grown at one of four densities, from two to 16 plants m(-2). For a given plant in any given density, the same tiller hierarchy applied for emergence of tillers, fertility of the emerged tillers and their subsequent grain number. These results were observed over a range of tiller fertility rates (from 7 to 91%), fertile tiller number per plant at maturity (from 0.2 to 4.7), and tiller contribution to grain yield (from 5 to 78 %). Tiller emergence was most probably related to assimilate supply and light quality. Development, fertility and contribution to yield of a specific tiller were highly dependent on growing conditions at the time of tiller emergence, particularly via early leaf area development of the tiller, which affected its subsequent leaf area accumulation. Assimilate availability in the main culm at the time of tiller emergence was the most likely early determinant of subsequent tiller fertility in this study.     

Tillering in grain sorghum over a wiide range of population densities: modelling dynamics of tiller fertility

The prediction of tillering is poor or absent in existing sorghum crop models even though fertile tillers contribute significantly to grain yield. The objective of this study was to identify general quantitative relationships underpinning tiller dynamics of sorghum for a broad range of assimilate availabilities. Emergence, phenology, leaf area development and fertility of individual main culms and tillers were quantified weekly in plants grown at one of four plant densities ranging from two to 16 plants m(-2). On any given day, a tiller was considered potentially fertile (a posteriori) if its number of leaves continued to increase thereafter. The dynamics of potentially fertile tiller number per plant varied greatly with plant density, but could generally be described by three determinants, stable across plant densities: tiller emergence rate aligned with leaf ligule appearance rate; cessation of tiller emergence occurred at a stable leaf area index; and rate of decrease in potentially fertile tillers was linearly related to the ratio of realized to potential leaf area growth. Realized leaf area growth is the measured increase in leaf area, whereas potential leaf area growth is the estimated increase in leaf area if all potentially fertile tillers were to continue to develop. Procedures to predict this ratio, by estimating realized leaf area per plant from intercepted radiation and potential leaf area per plant from the number and type of developing axes, are presented. While it is suitable for modelling tiller dynamics in grain sorghum, this general framework needs to be validated by testing it in different environments and for other cultivars.     

Effects of elevated ultraviolet-B radiation on native and cultivated plants of southern Africa

Seventeen herb, shrub and tree species of commercial and ecological importance in southern Africa were exposed at one location to ultraviolet-B (UV-B, 280-315 nm) radiation approx. 35 % above clear-sky background (control). The aims were to assess how UV-B affects canopy area, dry mass, and some biochemical and morphological properties of leaves, and to investigate whether differences between species are related to growth form of the plants. There was no pattern of response to UV-B related to growth form. Leaves of trees had altered chlorophyll a and b, carotenoid and flavonoid concentrations, but those of shrubs or herbs did not. Non-structural carbohydrates were unaffected. Smaller canopy areas and dry masses were observed under enhanced UV-B, but these were not statistically different among growth forms. There was a general insensitivity of species to elevated UV-B. Only five species had significantly altered leaf biochemical and morphological properties, canopy area and dry mass, the changes differing in magnitude. There was no consistent pattern of change in leaf thickness or biochemical composition with increased UV-B. Correlation analyses did not support the view that growth is less negatively affected in species with thick leaves or in those where leaf thickness increases, or in species with naturally high leaf flavonoid contents or that are able to synthesize additional flavonoids in response to UV-B enhancement. The analyses did not support the hypothesis that growth was inhibited by starch accumulation in leaves under elevated UV-B. However, changes in leaf shape did correlate with canopy area and dry mass, showing the importance of photomorphogenetic changes caused by UV-B which affect species' performance. We conclude that generalizations on plant sensitivity to UV-B based on growth form and functional type could be misleading, and that the great majority of economically important species of the region are likely to be insensitive to future UV-B increases. Notable exceptions include the Colophospermum mopane tree ecotypes chota and leslie and the arable annual Vigna unguiculata, both of which are traditional sources of livelihood to rural African populations and of importance to African industry and agriculture.     

On the conservative nature of the leaf mass-area relationship

In a previous empirical study, Hughes and colleagues showed that for several herbaceous species there is apparently a unique species-specific relationship between the area and mass of leaves. We tested this proposition using measurements from 15 broad-leaved species. We found that to a reasonable approximation, leaf area was proportional to leaf mass within a given species despite relatively large variations in both leaf thickness and the mass fraction of liquid matter. These observations show that the inverse density-thickness of leaves from a given species, which we call the Hughes constant, is approximately conserved. We conclude that the Hughes constant is likely to be more conservative than other traits traditionally used to describe leaves.