A method for studying histochemical reactions in intact human dentine with a polarizing incident light microscope

Localization and distribution of non-specific esterases has been studied in intact human dentine, by reflected light microscopy. The method of specimen preparation described here permits the visualization of optical sections in depth within the specimen at high optical resolution. Non-specific esterase was found deposited as discrete bands across the tubules. or as droplets, or as a diffuse microsomal variety in the dentinal tubules and in the interglobular spaces. It was possible to distinguish the droplet variety from the microsomal variety, of esterase within the same tubule, by means of a novel optical method using antiflex and differential interference contrast systems of reflected light microscopy. It was found that the coefficient of reflection of dentine diminished gradually from the enamel to the pre-dentine and was inversely related to the scattering of light in dentine. This scattering plays an important role in the formation of the image with reflected light microscopy. The reflected light microscope offers an economically attractive alternative or a supplementary mode of microscopy to the confocal scanning microscopes for studying intact dentine at varying depths.     

Morphological observation and characterization of the Pseudoregma bambucicola with the scanning electron microscope

Both leica microscopic camera system and scanning electron microscopy was used to observe and characterize the feet, back, abdomen, antennae and mouthparts of the Pseudoregma bambucicola from the bamboo, Bambusa multiplex. The possible functions of all the external morphological characteristics of the P. bambucicola were described and discussed in detail, which offers a basis for further enriching the biology, phylogeny and ecological niche of the P. bambucicola. Moreover, the morphological results should contribute to morphological identification and differentiation of the P. bambucicola from other aphids in the same family.     

Force spectroscopy reveals the presence of structurally modified dimers in transthyretin amyloid annular oligomers

Toxicity in amyloidogenic protein misfolding disorders is thought to involve intermediate states of aggregation associated with the formation of amyloid fibrils. Despite their relevance, the heterogeneity and transience of these oligomers have placed great barriers in our understanding of their structural properties. Among amyloid intermediates, annular oligomers or annular protofibrils have raised considerable interest because they may contribute to a mechanism of cellular toxicity via membrane permeation. Here we investigated, by using AFM force spectroscopy, the structural detail of amyloid annular oligomers from transthyretin (TTR), a protein involved in systemic and neurodegenerative amyloidogenic disorders. Manipulation was performed in situ , in the absence of molecular handles and using persistence length‐fit values to select relevant curves. Force curves reveal the presence of dimers in TTR annular oligomers that unfold via a series of structural intermediates. This is in contrast with the manipulation of native TTR that was more often manipulated over length scales compatible with a TTR monomer and without unfolding intermediates. Imaging and force spectroscopy data suggest that dimers are formed by the assembly of monomers in a head‐to‐head orientation with a nonnative interface along their β‐strands. Furthermore, these dimers stack through nonnative contacts that may enhance the stability of the misfolded structure.     

Setal morphology of grooming appendages in the spider crab,Libinia dubia

In crustaceans, grooming behaviors decrease fouling by removing debris from the exoskeleton and body structures; these grooming behaviors improve respiration, sensory reception, movement, and reproduction. Setal morphologies of the following grooming appendages in the decapod crustacean spider crab Libinia dubia are examined including the first pereiopod (cheliped), first, second, and third maxillipeds (mouthparts), and first, second, and third epipods (internal extensions of the maxillipeds). The objective of this study was to describe setal morphologies of these grooming appendages and to elucidate possible functions and efficiencies of setal structures. Spider crabs are hypothesized to have elaborate setal morphologies, mainly for cleaning specialized decorating setae as well as for cleaning inside the gill chamber, which has a higher likelihood of becoming fouled compared to other decapods such as shrimps. Fourteen setal types are documented and included several varieties of serrate and pappose setae as well as simple setae, cuspidate setae, papposerrate setae, and canoe setae. Maxillipodal epipods in the gill chamber are free of fouling, suggesting the setation on the third maxilliped protopod has an efficient functional morphology in removing debris before water enters the gill chamber. Serrate setae may function for detangling and separating structures whereas pappose setae may function for fine detailed grooming. The cheliped is the only grooming appendage that can reach decorating setae and it contains only pappose setae; thus decorating setae is not likely groomed in a manner that would greatly decrease fouling. J. Morphol. 277:1045–1061, 2016. © 2016 Wiley Periodicals, Inc.     

Endocytosis and Exocytosis Events Regulate Vesicle Traffic in Endothelial Cells

We used water-soluble styryl pyridinium dyes that fluoresce at the membrane-water interface to study vesicle traffic in endothelial cells. Cultured endothelial cells derived from bovine and human pulmonary microvessels were incubated in styryl probes, washed to remove dye from the plasmalemmal outer face, and observed by digital fluorescence microscopy. Vesicles that derived from plasmalemma by endocytosis were filled with the styryl dye. These vesicles were distributed throughout the cytosol as numerous particles of heterogeneous diameter and brightness. Vesicle formation was activated 2-fold following addition of extracellular albumin whereas a control protein, immunoglobulin G, had no effect. Dye uptake was abrogated by labeling at low temperatures and inhibitors of phosphoinositide-3-kinase (PI 3-kinase). Tyrosine kinase inhibitors (genistein and herbimycin A) prevented the albumin-induced vesicle formation. Cytochalasin B prevented vesicle redistribution indicating involvement of actin filaments in translocation of endosomes away from sites of vesicle formation. Styryl dye was lost from cells by exocytosis as evident by the disappearance of discrete fluorescent particles. N-ethylmaleimide and botulinum toxin types A and B caused cells to accumulate increased number of vesicles suggesting that exocytosis was regulated by NSF-dependent SNARE mechanism. The results suggest that phosphoinositide metabolism regulates endocytosis in endothelial cells and that extracellular albumin activates endocytosis by a mechanism involving tyrosine phosphorylation, whereas exocytosis is a distinct process regulated by the SNARE machinery. The results support the hypothesis that albumin regulates its internalization and release in vascular endothelial cells via activation of specific endocytic and exocytic pathways.     

The NADPH-dependent electron flow in chloroplasts of the higher plants

The NADPH-dependent reduction of some photosynthetic electron carriers in the dark, and the reduction of NADP+ associated with the glycolytic sequence and the oxidative pentose phosphate pathway in chloroplasts are reviewed. The postulated pathways of electron transports sensitive and insensitive to antimycin A are also evaluated. It is proposed that the electron flow, predominantly through cytochrome bf complex, may be also involved in the pathway of NADPH-dependent and antimycin A-insensitive back electron transport. An information on the chlororespiration in higher plants is also included. This revised version was published online in June 2006 with corrections to the Cover Date.     

Site-Specific Structural Variations Accompanying Tubular Assembly of the HIV-1 Capsid Protein

The 231-residue capsid (CA) protein of human immunodeficiency virus type 1 (HIV-1) spontaneously self-assembles into tubes with a hexagonal lattice that is believed to mimic the surface lattice of conical capsid cores within intact virions. We report the results of solid-state nuclear magnetic resonance (NMR) measurements on HIV-1 CA tubes that provide new information regarding changes in molecular structure that accompany CA self-assembly, local dynamics within CA tubes, and possible mechanisms for the generation of lattice curvature. This information is contained in site-specific assignments of signals in two- and three-dimensional solid-state NMR spectra, conformation-dependent ¹⁵N and ¹³C NMR chemical shifts, detection of highly dynamic residues under solution NMR conditions, measurements of local variations in transverse spin relaxation rates of amide ¹H nuclei, and quantitative measurements of site-specific ¹⁵N–¹⁵N dipole–dipole couplings. Our data show that most of the CA sequence is conformationally ordered and relatively rigid in tubular assemblies and that structures of the N-terminal domain (NTD) and the C-terminal domain (CTD) observed in solution are largely retained. However, specific segments, including the N-terminal β-hairpin, the cyclophilin A binding loop, the inter-domain linker, segments involved in intermolecular NTD–CTD interactions, and the C-terminal tail, have substantial static or dynamical disorder in tubular assemblies. Other segments, including the 3₁₀-helical segment in CTD, undergo clear conformational changes. Structural variations associated with curvature of the CA lattice appear to be localized in the inter-domain linker and intermolecular NTD–CTD interface, while structural variations within NTD hexamers, around local 3-fold symmetry axes, and in CTD–CTD dimerization interfaces are less significant.