DIPTEREX RESISTANCE IN THE HOUSEFLY AND THE SYNERGIC MECHANISM OF SV1 IN RELATION TO PENETRATION THROUGH CUTICLE

Abstract  SV₁ was observed to have obvious synergism and could delay housefly ( Musca domestica vicina ) resistance development to Dipterex. The penetration rates of Dipterex through housefly cuticle were determined in a susceptible and two resistant strains. The results indicated that the penetration in the resistant housefly strains was obviously slower than in the susceptible one. The penetrating rate of SV₁+ Dipterex (in mixture) was higher than that of Dipterex. The penetration reduction in resistant houseflies may be an important factor in bringing forth resistance. The increase of the penetrating rate of Dipterex and the decrease of its metabolic rate are regarded as the important mechanisms of SV₁ synergism to Dipterex.     

Penetration of soil aggregates of finite size

Summary Maximum penetrometer pressure was measured on artificial soil aggregates of finite size (2–29 mm) using blunt probes (total cone angle 60°) driven at 3 mm min⁻¹. Maximum penetrometer pressure increased asymptotically with increase in dimensionless aggregate radius,b/a, wherea andb are the probe and aggregate radii, respectively. A theory was developed for penetration of blunt probes into soil aggregates of finite size. The theory assumed that plastic failure occurs out to a radius,R, and that beyond this only elastic straining occurs. This theory can be applied to estimate the radial and tangential stresses adjacent to a blunt probe. The estimated radial and tangential stresses increased with increase in dimensionless aggregate radius,b/a. The radius of the plastic front,R, around the probe is predicted to increase with increased aggregate size. The results also demonstrate the effect of soil shear cohesion and internal friction angle onR. The results are discussed with reference to root penetration.     

Assessment of penetration of quantum dots through in vitro and in vivo human skin using the human skin equivalent model and the tape stripping method

Quantum dots (QDs) are rapidly emerging as an important class of nanoparticles (NPs) with potential applications in medicine. However, little is known about penetration of QDs through human skin. This study investigated skin penetration of QDs in both in vivo and in vitro human skin. Using the tape stripping method, this study demonstrates for the first time that QDs can actually penetrate through the stratum corneum (SC) of human skin. Transmission electron microscope (TEM) and energy diverse X-ray (EDX) analysis showed accumulation of QDs in the SC of a human skin equivalent model (HSEM) after dermal exposure to QDs. These findings suggest possible transdermal absorption of QDs after dermal exposure over a relatively long period of time.     

Reliability of wavefront shaping based on coherent optical adaptive technique in deep tissue focusing

Wavefront shaping can compensate the wavefront distortions in deep tissue focusing, leading to an improved penetration depth. However, when using the backscattered signals as the feedback, unexpected compensation bias may be introduced, resulting in focusing position deviations or even no focus in the illumination focal plane. Here we investigated the reliability of wavefront shaping based on coherent optical adaptive technique in deep tissue focusing by measuring the position deviations between the foci in the illumination focal plane and the epi‐detection plane. The experimental results show that when the penetration depth reaches 150 μm in mouse brain tissue (with scattering coefficient ~22.42 mm^?1) using a 488 nm laser and an objective lens with 0.75 numerical aperture, the center of the real focus will deviate out of one radius range of the Airy disk while the optimized focus in the epi‐detection plane maintained basically at the center. With the penetration depth increases, the peak to background ratio of the focus in the illumination focal plane decreases faster than that in the epi‐detection plane. The results indicate that when the penetration depth reaches 150 μm, feedback based on backscattered signals will make wavefront shaping lose its reliability, which may provide a guidance for applications of non‐invasive precise optogenetics or deep tissue optical stimulation using wavefront shaping methods. A, Intensity distribution in the epi‐detection plane and the illumination focal plane before and after correction, corresponding to brain sections with 250 and 300 μm thickness, respectively. Scale bar is 2 μm. B, Averaged focusing deviations in the epi‐detection plane (optimized) and the illumination focal plane (monitored) after compensation. The unit of the ordinate is one Airy disk diameter. Black dashed line represents one Airy disk radius. Bars represent the SE of each measurement set.      

High levels of arbuscular mycorrhizal fungus colonization on Medicago truncatula reduces plant suitability as a host for pea aphids (Acyrthosiphon pisum)

This study sheds light on a poorly understood area in insect-plant-microbe interactions,focusing on aphid probing and feeding behavior on plants with varying levels of arbuscular mycorrhizal(AM)fungus root colonization.It investigates a commonly occurring interaction of three species:pea aphid Acyrthosiphon pisum,barrel medic Medicago truncatula,and the AM fungus Rhizophagus irregularis,examining whether aphid-feeding behavior changes when insects feed on plants at different levels of AM fungus colonization(42% and 84% root length colonized).Aphid probing and feeding behavior was monitored throughout 8 h of recording using the electrical penetration graph(EPG)technique,also,foliar nutrient content and plant growth were measured.Summarizing,aphids took longer to reach their 1st sustained phloem ingestion on the 84% AM plants than on the 42% AM plants or on controls.Less aphids showed phloem ingestion on the 84% AM plants relative to the 42% AM plants.Shoots of the 84% AM plants had higher percent carbon(43.7%)relative to controls(40.5%),and the 84% AM plants had reduced percent nitrogen(5.3%)relative to the 42% AM plants(6%).In conclusion,EPG and foliar nutrient data support the hypothesis that modifications in plant anatomy(e.g.,thicker leaves),and poor food quality(reduced nitrogen)in the 84% AM plants contribute to reduced aphid success in locating phloem and ultimately to differences in phloem sap ingestion.This work suggests that M.truncatula plants benefit from AM symbiosis not only because of increased nutrient uptake but also because of reduced susceptibility to aphids.     

苜蓿假盘菌侵染苜蓿叶片的细胞学研究

采用微分干涉相差显微镜、扫描和透射电镜技术系统研究了苜蓿假盘菌Pseudopeziza medicaginis在苜蓿叶片的侵染过程及超微结构特征。结果表明，接种4h后，子囊孢子萌发产生芽管；12h后，芽管以直接侵入的方式进入表皮细胞形成侵染菌丝；24h后，表皮细胞中侵染菌丝向相邻表皮细胞扩展，同时侵入到叶肉细胞以胞内生长方式扩展；接种72h后，侵染菌丝在表皮细胞下的叶肉组织中形成初始菌落；第5d后，菌丝扩展至整个叶片组织，大量菌丝聚集形成子座组织，并进一步形成子囊盘与子囊。病菌菌丝在侵入寄主细胞初期，并不     

A functional nanocarrier that copenetrates extracellular matrix and multiple layers of tumor cells for sequential and deep tumor autophagy inhibitor and chemotherapeutic delivery

To further enhance the intensity of deep tumor drug delivery and integrate a combined therapy, we herein report on a core-shell nanocarrier that could simultaneously overcome the double barriers of the extracellular matrix (ECM) and multiple layers of tumor cells (MLTC). A pH-triggered reversible swelling-shrinking core and an MMP2 (matrix metallopeptidase 2) degradable shell were developed to encapsulate chemotherapeutics and macroautophagy/autophagy inhibitors, respectively. MMP2 degraded the shell, which was followed by the autophagy inhibitors' release. The exposed core could diffuse along the pore within the ECM to deliver chemotherapeutics into deep tumors, and it was able to swell in lysosomes and shrink back in the cytoplasm or ECM. The swelling of the core resulted in the rapid release of chemotherapeutics to kill autophagy-inhibited cells. After leaving the dead cells, the shrinking core could act on neighboring cells that were closer to the center of the tumor. The core thus could also cross MLTC layer by layer to deliver chemotherapeutics into the deep tumor.     

Ex vivo thickness measurement of cartilage covering the temporomandibular joint

Articular cartilage covers the temporomandibular joint (TMJ) and provides smooth and nearly frictionless articulation while distributing mechanical loads to the subchondral bone. The thickness of the cartilage is considered to be an indicator of the stage of development, maturation, aging, loading history, and disease. The aim of our study was to develop a method for ex vivo assessment of the thickness of the cartilage that covers the TMJ and to compare that with two other existing methods. Eight porcine TMJ condyles were used to measure cartilage thickness. Three different methods were employed: needle penetration, micro-computed tomography (micro-CT), and histology; the latter was considered the gold standard. Histology and micro-CT scanning results showed no significant differences between thicknesses throughout the condyle. Needle penetration produced significantly higher values than histology, in the lateral and anterior regions. All three methods showed the anterior region to be thinner than the other regions. We concluded that overestimated thickness by the needle penetration is caused by the penetration of the needle through the first layer of subchondral bone, in which mineralization is less than in deeper layers. Micro-CT scanning method was found to be a valid method to quantify the thickness of the cartilage, and has the advantage of being non-destructive.     

镉、铅及其复合污染对大麦幼苗部分生理指标的影响

以Cd、Pb为胁迫因子，以大麦为试验材料，采用室内培养法，研究了重金属Cd﹑Pb及复合污染不同时间（3、5d）对大麦幼苗叶片部分生理指标的影响。结果表明，随着 Cd﹑Pb及Cd+Pb处理浓度的增加，大麦幼苗叶片中可溶性糖的含量表现为先升后降。在Cd﹑Pb单一处理条件下，不同浓度Cd﹑Pb均可造成叶细胞膜透性增大，叶片的相对电导率和脯氨酸含量上升。不同浓度的Cd+Pb复合处理对叶细胞膜的损伤均大于单一处理，低浓度Cd+Pb（5+50 mg·L^-1）复合处理组的可溶性糖含量比单一处理高。在不同处理时间（3、5d）内，所有Cd+Pb复合处理组叶中脯氨酸含量均高于单一处理组，Cd﹑Pb复合处理对脯氨酸的积累有促进作用。单一处理中Cd对大麦幼苗的毒性比Pb大，而复合处理（Cd+Pb）对大麦幼苗的损伤和毒害作用比单一处理更为严重，其交互作用机理值得进一步研究。