Cytochemistry and freeze-fracture of membranes isolated from the electrocyte of Electrophorus electricus (L.)

Summary Membranes were isolated from the main electric organ of Electrophorus electricus and studied by means of cytochemistry and freezefracture. The membrane fractions consisted of vesicles inside-in as determined by localization of anionic sites using colloidal iron and cationized ferritin particles. The anionic sites were not homogeneously distributed on the surface of the vesicle. Freeze-fracture showed the presence of intramembranous particles associated with either protoplasmic (P) or extracellular (E) faces of the membrane. Regions of the membrane without particles were observed. The results are discussed in relation to the existence of association between intramembranous particles and membrane receptors.For all correspondence     

Preferred egg laying sites in Palmacorixa nana (Heteroptera : Corixidae)

Female Palmacorixa nana showed clear preference for wood oviposition substrates over Elodea and plexiglass in both laboratory and field experiments. Wood was chosen because of its rigidity and rough surface. These data raise the possibility that males could gain access to females by controlling localized resources.Present address: Department 0f Entomology University 0f Alberta Edmonton, Alberta, Canada T6 G 2E3Present address: Department 0f Entomology University 0f Alberta Edmonton, Alberta, Canada T6 G 2E3     

The vanishing clone: karyotypic evidence for extensive intraclonal genetic variation in the peach potato aphid,Myzus persicae (Hemiptera: Aphididae)

Analysis of holocentric mitotic metaphase chromosomes of the peach‐potato aphid Myzus persicae (Sulzer) clone 33H revealed different chromosome numbers, ranging from 12 to 17 within each embryo, in contrast to the standard karyotype of this species (2n = 12). Chromosome length measurements revealed that the observed chromosomal mosaicism is the result of recurrent fragmentations of chromosomes X, 1 and 3 because of fragile sites or hot spots of recombination. Fluorescent in situ hybridization experiments showed that X chromosomes were frequently involved in recurrent fragmentations, in particular their telomeric end opposite to the nucleolar organizer region. Experiments to induce males showed that M. persicae clone 33H is obligately parthenogenetic. The reproduction by apomictic parthenogenesis, together with a high telomerase expression that stabilized the chromosomes involved in the fragmentations observed in the M. persicae clone 33H, appears to favour the stabilization of the observed chromosome instability. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 350–358.     

Rational Design of Nanocatalysts with Nonmetal Species Modification for Electrochemical CO2 Reduction

Converting CO₂ to valuable carbonaceous fuels and chemicals via electrochemical CO₂ reduction by using renewable energy sources is considered to be a scalable strategy with substantial environmental and economic benefits. One of the challenges in this field is to develop nanocatalysts with superior electrocatalytic activity and selectivity for targeted products. Nonmetal species modification of nanocatalysts is of great significance for the construction of distinctive active sites to overcome the kinetic limitations of CO₂ reduction. These types of modification enable the efficient control of the selectivity and significantly decrease the reaction overpotential. Herein, a comprehensive review of the recent progress of nonmetal species modification of nanocatalysts for electrochemical CO₂ reduction is presented. After discussing some fundamental parameters and the basic principles of CO₂ reduction, including possible reaction pathways in light of theoretical modeling and experiments, the identification of active sites and elucidation of reaction mechanisms are emphasized for unraveling the role of nonmetal species modification, such as heteroatom incorporation, organic molecule decoration, electrolyte engineering, and single‐atom engineering. In the final section, future challenges and constructive perspectives are provided, facilitating the accelerated advancement of mechanism research and practical applications of green carbon cycling.     

Miro: A molecular switch at the center of mitochondrial regulation

The orchestration of mitochondria within the cell represents a critical aspect of cell biology. At the center of this process is the outer mitochondrial membrane protein, Miro. Miro coordinates diverse cellular processes by regulating connections between organelles and the cytoskeleton that range from mediating contacts between the endoplasmic reticulum and mitochondria to the regulation of both actin and microtubule motor proteins. Recently, a number of cell biological, biochemical, and protein structure studies have helped to characterize the myriad roles played by Miro. In addition to answering questions regarding Miro's function, these studies have opened the door to new avenues in the study of Miro in the cell. This review will focus on summarizing recent findings for Miro's structure, function, and activity while highlighting key questions that remain unanswered.     

Application of an optimized marker amplification protocol in immunohistochemistry — a valuable tool for visualizing antigenic sites of low signal strength or sparse distribution

Amplification of immunohistochemical markers received considerable attention during the 1980s and 1990s. The amplification approach was largely abandoned following the development of antigen retrieval and reporter amplification techniques, because the latter were incorporated more easily into high throughput automated procedures in industrial and diagnostic laboratories. There remain, however, a number of instances where marker amplification still has much to offer. Consequently, we examined experimentally the utility of an optimized marker amplification technique in diagnostically relevant tissue where either the original signal strength was low or positive sites were visible, but sparsely distributed. Marker amplification in the former case not only improved the visibility of existing positive sites, but also revealed additional sites that previously were undetectable. In the latter case, positive sites were rendered more intense and therefore more easily seen during low magnification examination of large areas of tissue.     

Amyloid from a histochemical perspective. A review of the structure,properties and types of amyloid,and a proposed staining mechanism for Congo red staining

Amyloid is a diverse group of unrelated peptides or proteins that have positive functionality or are associated with various pathologies. Despite vast differences, all amyloids share several features that together uniquely define the group. 1) All amyloids possess a characteristic cross-ß pattern with X-ray diffraction typical of ß-sheet secondary protein structures. 2) All amyloids are birefringent and dichroic under polarizing microscopy after staining with Congo red, which indicates a crystalline-like (ordered) structure. 3) All amyloids cause a spectral shift in the peak wavelength of Congo red with conventional light microscopy due to perturbation of π electrons of the dye. 4) All amyloids show heightened intensity of fluorescence with Congo red, which suggests an unusual degree of packing of the dye onto the substrate. The ß portion of amyloid molecules, the only logical substrate for specific Congo red staining under histochemical conditions, consists of a stack of ß-sheets laminated by hydrophilic and hydrophobic interactions between adjacent pairs. Only the first and last ß-sheets are accessible to dyes. Each sheet is composed of numerous identical peptides running across the width of the sheet and arranged in parallel with side chains in register over the length of the fibril. Two sets of grooves are bordered by side chains. X grooves run perpendicular to the long axis of the fibril; these grooves are short (the width of the sheet) and number in the hundreds or thousands. Y grooves are parallel with the long axis. Each groove runs the entire length of the fibril, but there are very few of them. While Congo red is capable of ionic bonding with proteins via two sulfonic acid groups, physical constraints on the staining solution preclude ionic interactions. Hydrogen bonding between dye amine groups and peptide carbonyls is the most likely primary bonding mechanism, because all ß-sheets possess backbone carbonyls. Various amino acid residues may form secondary bonds to the dye via any of three van der Waals forces. It is possible that Congo red binds within the Y grooves, but that would not produce the characteristic staining features that are the diagnostic hallmarks of amyloid. Binding in the X grooves would produce a tightly packed series of dye molecules over the entire length of the fibril. This would account for the signature staining of amyloid by Congo red: dichroic birefringence, enhanced intensity of fluorescence and a shift in visible absorption wavelength.