高动态光学血管造影成像

我们提出一种高动态光学血管造影成像(HDOA)方法来实现活体生物样本血管造影成像.该方法通过设置高动态范围曝光时间,依据动态积分效应和吸收效应以实现高动态积分时间调制.通过该方法,不仅能够同时获得各级血管清晰的造影图像,还能消除样品厚度不均、吸收系数不同对成像造成的影响.论文以仿体和活体金鱼为样品,通过实验验证了HDOA方法根据动态积分调制效应和吸收效应,能有效实现各级血管同时成像.     

Wind‐mediated horseweed (Conyza canadensis) gene flow: pollen emission,dispersion, and deposition

Horseweed (Conyza canadensis) is a problem weed in crop production because of its evolved resistance to glyphosate and other herbicides. Although horseweed is mainly self-pollinating, glyphosate-resistant (GR) horseweed can pollinate glyphosate-susceptible (GS) horseweed. To the best of our knowledge, however, there are no available data on horseweed pollen production, dispersion, and deposition relative to gene flow and the evolution of resistance. To help fill this knowledge gap, a 43-day field study was performed in Champaign, Illinois, USA in 2013 to characterize horseweed atmospheric pollen emission, dispersion, and deposition. Pollen concentration and deposition, coupled with atmospheric data, were measured in a source field (180 m by 46 m) and its surrounding areas up to 1 km downwind horizontally and up to 100 m vertically. The source strength (emission rate) ranged from 0 to 140 pollen grains per plant per second (1170 to 2.1×10⁶ per plant per day). For the life of the study, the estimated number of pollen grains generated from this source field was 10.5×10¹⁰ (2.3×10⁶ per plant). The release of horseweed pollen was not strongly correlated to meteorological data and may be mainly determined by horseweed physiology. Horseweed pollen reached heights of 80 to100 m, making long-distance transport possible. Normalized (by source data) pollen deposition with distance followed a negative-power exponential curve. Normalized pollen deposition was 2.5% even at 480 m downwind from the source edge. Correlation analysis showed that close to or inside the source field at lower heights (≤3 m) vertical transport was related to vertical wind speed, while horizontal pollen transport was related to horizontal wind speed. High relative humidity prevented pollen transport at greater heights (3–100 m) and longer distances (0–1000 m) from the source. This study can contribute to the understanding of how herbicide-resistance weeds or invasive plants affect ecology through wind-mediated pollination and invasion.     

Active aggregation among sexes in bean flower thrips (Megalurothrips sjostedti) on cowpea (Vigna unguiculata)

Male sexual aggregations are a common territorial, mating‐related or resource‐based, behaviour observed in diverse organisms, including insects such as thrips. The influence of factors such as plant substrate, time of day, and geographic location on aggregation of thrips is uncertain, therefore we monitored the dispersion of male and female bean flower thrips (BFT), Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), on cowpea, Vigna unguiculata (L.) Walp. (Fabaceae), over three cowpea growth stages and across three cowpea‐growing areas of Kenya. Our results indicated that for all the crop growth stages, the density of BFTs varied over the time of day, with higher densities at 10:00, 13:00, and 16:00 hours than at 07:00 hours. Thrips densities did not differ among blocks at the budding stage, but they did at peak flowering and podding stages. Dispersion indices suggested that both male and female BFTs were aggregated. Active male aggregation occurred only on green plant parts and it varied across blocks, crop stages, and locations. Similarly, active female aggregation was observed in peak flowering and podding stages. Such active aggregation indicates a semiochemical or behaviour‐mediated aggregation. Identification of such a semiochemical may offer new opportunities for refining monitoring and management strategies for BFT on cowpea, the most important grain legume in sub‐Saharan Africa.     

Investigation of optical attenuation imaging using optical coherence tomography for monitoring of scars undergoing fractional laser treatment

We demonstrate the use of the near‐infrared attenuation coefficient, measured using optical coherence tomography (OCT), in longitudinal assessment of hypertrophic burn scars undergoing fractional laser treatment. The measurement method incorporates blood vessel detection by speckle decorrelation and masking, and a robust regression estimator to produce 2D en face parametric images of the attenuation coefficient of the dermis. Through reliable co‐location of the field of view across pre‐ and post‐treatment imaging sessions, the study was able to quantify changes in the attenuation coefficient of the dermis over a period of ～20 weeks in seven patients. Minimal variation was observed in the mean attenuation coefficient of normal skin and control (untreated) mature scars, as expected. However, a significant decrease (13 ± 5%, mean ± standard deviation) was observed in the treated mature scars, resulting in a greater distinction from normal skin in response to localized damage from the laser treatment. By contrast, we observed an increase in the mean attenuation coefficient of treated (31 ± 27%) and control (27 ± 20%) immature scars, with numerical values incrementally approaching normal skin as the healing progressed. This pilot study supports conducting a more extensive investigation of OCT attenuation imaging for quantitative longitudinal monitoring of scars.

En face 2D OCT attenuation coefficient map of a treated immature scar derived from the pre‐treatment (top) and the post‐treatment (bottom) scans. (Vasculature (black) is masked out.) The scale bars are 0.5 mm.     

液体培养条件下细菌浓度两种测定方法比较

液体培养细菌后,分别测定培养液、培养液沉淀 无菌盐水的吸光度,结果存在明显差异。采用稀释平板法和显微计数法测定了培养液中细菌数量,并推导出嗜水气单胞菌活菌数与吸光度的关系为logI0/I=6.848×10-25·C。     

Band-selective 13C Homonuclear 3D Spectroscopy for Solid Proteins at High Field with Rotor-synchronized Soft Pulses

We demonstrate improved 3D ¹³C–¹³C–¹³C chemical shift correlation experiments for solid proteins, utilizing band-selective coherence transfer, scalar decoupling and homonuclear zero-quantum polarization transfer. Judicious use of selective pulses and a z-filter period suppress artifacts with a two-step phase cycle, allowing higher digital resolution in a fixed measurement time. The novel correlation of C^ali–C^ali–CX (C^ali for aliphatic carbons, CX for any carbon) reduces measurement time by an order of magnitude without sacrificing digital resolution. The experiment retains intensity from side-chain carbon resonances whose chemical shift dispersion is critical to minimize spectral degeneracy for large proteins with a predominance of secondary structure, such as β-sheet rich fibrillar proteins and α-helical membrane proteins. We demonstrate the experiment for the β1 immunoglobulin binding domain of protein G (GB1) and fibrils of the A30P mutant of α-synuclein, which is implicated in Parkinson’s disease. Selective pulses of duration comparable the rotor period give optimal performance, but must be synchronized with the spinning in non-trivial ways to minimize chemical shift anisotropy recoupling effects. Soft pulses with a small bandwidth-duration product are best for exciting the ~70 ppm bandwidth required for aliphatic-only dimensions.     

Structural analysis of the PP2C phosphatase tPphA from Thermosynechococcus elongatus: a flexible flap subdomain controls access to the catalytic site

The homologue of the phosphoprotein PII phosphatase PphA from Thermosynechococcus elongatus, termed tPphA, was identified and its structure was resolved in two different space groups, C222₁ and P4₁2₁2, at a resolution of 1.28 and 3.05 Å, respectively. tPphA belongs to a large and widely distributed subfamily of Mg²⁺/Mn²⁺-dependent phosphatases of the PPM superfamily characterized by the lack of catalytic and regulatory domains. The core structure of tPphA shows a high degree of similarity to the two PPM structures identified so far. In contrast to human PP2C, but similar to Mycobacterium tuberculosis phosphatase PstP, the catalytic centre exhibits a third metal ion in addition to the dinuclear metal centre universally conserved in all PPM members. The fact that the third metal is only liganded by amino acids, which are universally conserved in all PPM members, implies that the third metal could be general for all members of this family. As a specific feature of tPphA, a flexible subdomain, previously recognized as a flap domain, could be revealed. Comparison of different structural isomers of tPphA as well as site-specific mutagenesis implied that the flap domain is involved in substrate binding and catalytic activity. The structural arrangement of the flap domain was accompanied by a large side-chain movement of an Arg residue (Arg169) at the basis of the flap. Mutation of this residue strongly impaired protein stability as well as catalytic activity, emphasizing the importance of this amino acid for the regional polysterism of the flap subdomain and confirming the assumption that flap domain flexibility is involved in catalysis.     

The first crystal structure of gluconolactonase important in the glucose secondary metabolic pathways

The first gluconolactonase crystal structure from bacteria has been determined to a resolution of 1.61 Å using X-ray crystallography. It belongs to the senescence marker protein 30/gluconolaconase superfamily but exhibits substrate specificity mainly toward d-glucono-δ-lactone. It forms a novel disulfide-bonded clamshell dimer comprising two doughnut-shaped six-bladed β-propeller domains, yet with an exceptionally long N-terminal subdomain forming an extra helix and four additional β-strands to enclose half of the outermost β-strands of each propeller. Extensive interactions, including H-bonds, salt bridges, disulfide bonds, and coordination bonds, along with numerous bridging water molecules, are present in the interface to institute the “top-to-top” clamshell-type dimer. Three calcium ions per subunit were observed. Two are present in the central water-filled channel, with the top one coordinated to four highly conserved amino acids and is possibly involved in substrate hydrolysis, while the bottom one is coordinated to the backbone oxygen atoms, which is possibly for stabilizing the propeller domain. One calcium ion is situated in the interface also to stabilize the dimer form. Since gluconolactonase is essential in the glucose secondary metabolic pathways leading to the synthesis of pentose, vitamin C, or “antiaging” factors, determination of its tertiary structure should help understand these important biochemical processes.     

A fibre optic catheter for simultaneous measurement of longitudinal and circumferential muscular activity in the gastrointestinal tract

Diagnostic catheters based on fibre Bragg gratings (FBG's) are proving to be highly effective for measurement of the muscular activity associated with motility in the human gut. While the primary muscular contractions that generate peristalsis are circumferential in nature, it has long been known that there is also a component of longitudinal contractility present, acting in harmony with the circumferential component to improve the overall efficiency of material movement. We report the detection of longitudinal motion in mammalian intestine using an FBG technique that should be viable for similar detection in humans. The longitudinal sensors have been combined with our previously reported FBG pressure sensing elements to form a composite catheter that allows the relative phase between the two components to be detected. The catheter output has been validated using video mapping in an ex‐vivo rabbit ileum preparation. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)