Ultrastructural analysis of midgut cells from Culex quinquefasciatus (Diptera: Culicidae) larvae resistant to Bacillus sphaericus

The larvicidal action of the entomopathogen Bacillus sphaericus towards Culex quinquefasciatus is due to the binary (Bin) toxin present in crystals, which are produced during bacterial sporulation. The Bin toxin needs to recognize and bind specifically to a single class of receptors, named Cqm1, which are 60-kDa α-glucosidases attached to the apical membrane of midgut cells by a glycosylphosphatidylinositol anchor. C. quinquefasciatus resistance to B. sphaericus has been often associated with the absence of the α-glucosidase Cqm1 in larvae midgut microvilli. In this work, we aimed to investigate, at the ultrastructural level, the midgut cells from C. quinquefasciatus larvae whose resistance relies on the lack of the Cqm1 receptor. The morphological analysis showed that midgut columnar cells from the resistant larvae are characterized by a pronounced production of lipid inclusions, throughout the 4th instar. At the end of this stage, resistant larvae had an increased size and number of these inclusions in the midgut cells, while only a small number were observed in the cells from susceptible larvae. The morphological differences in the midgut cells of resistant larvae found in this work suggested that the lack of the Cqm1 receptor, which also has a physiological role as being an α-glucosidase, can be related to changes in the cell metabolism. The ultrastructural effects of Bin toxin on midgut epithelial cells from susceptible and resistant larvae were also investigated. The cytopathological alterations observed in susceptible larvae treated with a lethal concentration of toxin included breakdown of the endoplasmic reticulum, mitochondrial swelling, microvillar disruption and vacuolization. Some effects were observed in cells from resistant larvae, although those alterations did not lead to larval death, indicating that the receptor Cqm1 is essential to mediate the larvicidal action of the toxin.This is the first ultrastructural study to show differences in the cell morphology of resistant larvae and further investigation is needed to understand the impact of the lack of expression of midgut enzymes on the physiology of resistant insects.     

A note on the Joint Embedding Property in Fragments of Arithmetic

It is known that full Peano Arithmetic does not have the jointembedding property(JEP). At the other extreme of the hierarchy,Open Induction also fails to have this property. We prove, using some conservation results about fragments ofarithmetic, that if T is a theoryconsistent with PA and T I (bounded existential parameter-freeinduction), then any two m dels of PA which jointly embed ina model of T also jointly embed in an elementary extension ofone of them. In particular, any fragment of PA extending I fails to have JEP.     

Uptake of silver nanoparticles by monocytic THP-1 cells depends on particle size and presence of serum proteins

Human health risks by silver nanoparticle (AgNP) exposure are likely to increase due to the increasing number of NP-containing products and demonstrated adverse effects in various cell lines. Unfortunately, results from (toxicity) studies are often based on exposure dose and are often measured only at a fixed time point. NP uptake kinetics and the time-dependent internal cellular concentration are often not considered. Macrophages are the first line of defense against invading foreign agents including NPs. How macrophages deal with the particles is essential for potential toxicity of the NPs. However, there is a considerable lack of uptake studies of particles in the nanometer range and macrophage-like cells. Therefore, uptake rates were determined over 24 h for three different AgNPs sizes (20, 50 and 75 nm) in medium with and without fetal calf serum. Non-toxic concentrations of 10 ng Ag/mL for monocytic THP-1 cells, representing realistic exposure concentration for short-term exposures, were chosen. The uptake of Ag was higher in medium without fetal calf serum and showed increasing uptake for decreasing NP sizes, both on NP mass and on number basis. Internal cellular concentrations reached roughly 32/10 %, 25/18 % and 21/15 % of the nominal concentration in the absence of fetal calf serum/with fetal calf serum for 20-, 50- and 75-nm NPs, respectively. Our research shows that uptake kinetics in macrophages differ for various NP sizes. To increase the understanding of the mechanism of NP toxicity in cells, the process of uptake (timing) should be considered.     

Varactor-tuned gunn diode voltage controlled oscillator antenna array

A simple varactor tuned X-band Gunn diode VCO antenna array which is strongly coupled has been demonstrated. These arrays have the advantages of simple biasing circuit, no resistors required to eliminate multimode problem and suitable for monolithic integration circuit. Preliminary results show a maximum tuning range of 47MHz for 1×1 array and 170MHz for 2×2 array. In order to solve power combining heating problem, we move the backside metal forward and it becomes a microstrip form. The measured frequency and radiation patterns of these grid arrays agree very well with theoretical calculations.     

Variable angle NMR spectroscopy and its application to the measurement of residual chemical shift anisotropy

The successful measurement of anisotropic NMR parameters like residual dipolar couplings (RDCs), residual quadrupolar couplings (RQCs), or residual chemical shift anisotropy (RCSA) involves the partial alignment of solute molecules in an alignment medium. To avoid any influence of the change of environment from the isotropic to the anisotropic sample, the measurement of both datasets with a single sample is highly desirable. Here, we introduce the scaling of alignment for mechanically stretched polymer gels by varying the angle of the director of alignment relative to the static magnetic field, which we call variable angle NMR spectroscopy (VA-NMR). The technique is closely related to variable angle sample spinning NMR spectroscopy (VASS-NMR) of liquid crystalline samples, but due to the mechanical fixation of the director of alignment no sample spinning is necessary. Also, in contrast to VASS-NMR, VA-NMR works for the full range of sample inclinations between 0° and 90°. Isotropic spectra are obtained at the magic angle. As a demonstration of the approach we measure 13C-RCSA values for strychnine in a stretched PDMS/CDCl? gel and show their usefulness for assignment purposes. In this context special care has been taken with respect to the exact calibration of chemical shift data, for which three approaches have been derived and tested.     

Analysis of HRTEM images for carbon nanostructure quantification

Image processing algorithms have been developed to extract fringe length, tortuosity and separation from high resolution transmission electron microscopy images. To validate the separation algorithm, a comparison is made between the image-based fringe separation and that obtained by analysis of X-ray diffraction data for a progressively heat-treated carbon black. Agreement is favorable. To illustrate the utility of the analysis parameters for a range of carbon nanostructures, analysis is applied to a series of pyrolytically prepared carbon soots – qualitatively described as containing amorphous, graphitic or fullerenic nanostructure. For all processing, the intermediate image, in the form of a skeletonized binary image of the original high resolution transmission electron micrograph, is shown and found to accurately reflect the nanostructural organization within the carbon as visually observed. Statistical results for each analysis parameter, extracted from the binary images, are presented in the form of histograms and quantitatively distinguish the different carbon nanostructures.     

Cytoplasmic RNA and nuclear changes detected cytochemically during the degeneration of salivary glands of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari, Ixodidae)

The present study reports cytochemistry data about salivary glands of females (unfed, engorged, and at day three post-engorgement) and males (unfed, at day seven post-attachment, and at days three and seven post-detachment from the host) of the tick Rhipicephalus sanguineus. The results revealed nuclear changes in engorged females and at day three post-engorgement, and in males in all stages (except unfed). These changes were more prominent in females. Cytoplasmic changes were also observed in cells of all acini of males and females. In types II and III acini of engorged females, nuclear changes were observed in the shape (irregular, with blebs, fragmenting or fragmented), size (enlarged or reduced), and arrangement and condensation level of chromatin (marginal or as blebs). Changes were also detected in nucleoli, regarding their shape (fragmenting or fragmented), size (enlarged), and location (central, marginal or as blebs). Some nucleoli were also compacted or disorganized. In females at day three pos-engorgement, all acini exhibited similar changes to those observed in engorged females. RNA staining was stronger in cells of engorged females than those at day three post-engorgement. In males at day seven post-attachment, cells of types II, III, IV acini presented changes in the size of the nucleus and condensation level of chromatin similar to those of females. The shape of the nucleus was round, irregular or undergoing fragmentation, and the chromatin was located at the margin or throughout the nucleus. The changes in the nucleolus were similar to those of females, regarding size and organization, although round-shaped and in the central location. In males at day three post-detachment, cells of all acini exhibited nuclear changes similar to those of males at day seven post-attachment, in addition to the fragmentation of the nucleolus. At day seven post-detachment, changes were detected in all acini similar to the observed in males at day seven post-attachment. Regarding cytoplasmic RNA, staining was prominent in males at day seven post-attachment and weak in those at day seven post-detachment from the host. In females as well as males, different RNA staining patterns in the cytoplasm and nuclear changes characterized apoptotic cell death.     

Modifications of interface chemistry of LSM-YSZ composite by ceria nanoparticles

A porous composite electrode LSM-YSZ (lanthanum strontium manganite and yttria stabilized zirconia) was impregnated with different amounts of SDC (samarium substituted ceria) nanoparticles. The materials were investigated with X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy to determine the microstructure, the interface chemistry and the surface chemistry of the various impregnated samples. The SDC nanoparticles cover the surface of the LSM-YSZ backbone to a large extent; they are approximately 5-20 nm in diameter and have a cubic crystal structure. Low concentrations of lanthanum and manganese originating from LSM were detected within SDC particles. It was also observed that the relative atomic concentration of strontium increased on the LSM-YSZ surface with increasing amount of SDC nanoparticles. These findings are related to the applied nanoparticle impregnation method. It is indicated that interactions between surfactant, nanoparticles, impregnation solution and the LSM-YSZ composite take place which can locally affect the surface and interface chemistry of the investigated materials.