Probing hemoglobin confinement inside submicron silica tubes using synchrotron SAXS and electrochemical response

The configuration of hemoglobin in solution and confined inside silica nanotubes has been studied using synchrotron small angle X-ray scattering and electrochemical activity. Confinement inside submicron tubes of silica aid in preventing protein aggregation, which is vividly observed for unconfined protein in solution. The radius of gyration (R-g) and size polydispersity (p) of confined hemoglobin was found to be lower than that in solution. This was also recently demonstrated in case of confined hemoglobin inside layered polymer capsules. The confined hemoglobin displayed a higher thermal stability with Rg and p showing negligible changes in the temperature range 25-75 degrees C. The differences in configuration between the confined and unconfined protein were reflected in their electrochemical activity. Reversible electrochemical response (from cyclic voltammograms) obtained in case of the confined hemoglobin, in contrary to the observance of only a cathodic response for the unconfined protein, gave direct indication of the differences between the residences of the electroactive heme center in a different orientation compared to that in solution state. The confined Hb showed loss of reversibility only at higher temperatures. The electron transfer coefficient (alpha) and electron transfer rate constant (k(s)) were also different, providing additional evidence regarding structural differences between the unconfined and confined states of hemoglobin. Thus, absence of any adverse effects due to confinement of proteins inside the inorganic matrices such as silica nanotubes opens up new prospects for utilizing inorganic matrices as protein ``encapsulators'', as well as sensors at varying temperatures.

Time-dependent nanoscale plasticity in nanocrystalline nickel rods and tubes

Time-dependent nanoscale plasticity of nanocrystalline nickel at room temperature was critically explored through a series of micropillar creep and quasi-static compression experiments on rod and tube specimens fabricated by electron beam lithography and electroplating. Enhanced creep rates in tubes as compared to rods, establishes the facilitating role played by the free surface in time-dependent deformation. Creep stress exponent, n, and strain-rate sensitivity, m, were compared to examine connections between creep and the rate-dependent plasticity, if any. (C) 2015 Elsevier Ltd. All rights reserved.

Investigation on Nonequlibrium Radiation and Relaxation Phenomena in Shock Tubes

The experimental results for the excited time of the nonequlibrium radiation and the ionization behind strong shock waves are presented. Using an optical multichannel analyzer, InSb infrared detectors and near-free-molecular Langmuir probes, the infrared radiation, the electron density of air and the nonequilibrium radiation spectra at different moments of the relaxation process in nitrogen test gas behind normal shock waves were obtained, respectively, in hydrogen oxygen combustion driven shock tubes.

Preparation of Ga2O3 nanoribbons and tubes by electrospinning

A simple way to synthesize beta-Ga2O3 nanoribbons and tubes by electrospinning is introduced. The diameters of the electrospun fibers range from 150 nm to 2.5 mu m and their lengths reach up to several millimeters. The relationship among precursors, precursor concentrations, and crystal growth of beta-Ga2O3 nanoribbons and tubes are discussed. The structures of beta-Ga2O3 fibers have been investigated by various methods such as thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction, FT-IR, Raman spectra, scanning electron micrograph (SEM), and transmission electron micrograph (TEM).

Electron microscopic features of experimental choroidal neovascularization

We produced choroidal neovascularization in the rhesus monkey by diminishing the blood supply to the inner retina and producing defects in Bruch's membrane by photocoagulation. The neovascular fronds which developed either infiltrated the subretinal space or proliferated through necrotic and gliotic retina into the vitreous cavity. Sequential electron microscopic sections of neovascular fronds in the subretinal space demonstrated that the advancing capillary sprouts were composed of primitive endothelial tubes surrounded by pericytes and enmeshed in a loose basement-membrane-like substance. More mature capillaris and displayed endothelial fenestrations and endothelial-pericyte membranous contacts. Large neovascular fronds developed major feeding vessels that closely resembled normal small choroidal arteries and veins. Retinal pigment epithelial cells in various guises were in constant association with proliferating neovascular networks.

Light and electron microscope studies of host-parasite relations in a mycoparasite

Light microscope studies of the mycoparasite Piptocephalis virginiana revealed that the cylindrical spores of the parasite became spherical upon germination and produced 1-4 germ tubes. Generally t"l.vO germ tubes were produced by each spore. When this parasite was inoculated on its potential hosts, Choanephora cucurbitarum and Phascolomyces articulosus, the germ tube nearest to the host hypha continued to grow and made contact with the host hypha. The tip of the parasite's germ tube became swollen to form a distinct appressorium. Up to this stage the behavior of the parasite was similar regardless of the nature of the host. In the compatible host-parasite combination, the parasite penetrated the host, established a nutritional relationship and continued to grow to cover the host completely with its buff colored spores in 3-4 days. In the incompatible host-parasite combination, the parasite penetrated the host but its further advance was arrested. As a result of failure to establish a nutritional relationship with the resistant host, the parasite made further attempts to penetrate the host at different sites producing multiple infections. In the absence of nutrition the parasite weakened and the host outgrew the parasite completely. In the presence of a non-host species, Linderina pennispora the parasite continued to grow across the non-host 1).yp_hae vlithout establishing an initial contact. Germination studies showed that the parasite germinated equally well in the presence of host and non-host species. Further electron microscope studies revealed that the host-parasite interaction between P. virginiana and its host, C. cucurbi tarum, was compatible when the host hyphae were young slender, with a thin cell wall of one layer. The parasite appeared to penetrate mechanically by pushing the host-cell wall inward. The host plasma membrane invaginated along the involuted cell wall. The older hyphae of C. cucurbitarum possessed two distinct layers of cell wall and-showed an incompatible interaction when challenged vlith the parasite. At the point of contact, the outer layer of the host-cell wall dissolved, probably by enzymatic digestion, and the inner layer became thickened and developed a papilla as a result of its response to the parasite. The haustoria of the parasite in the old hyphae were always surrounded by a thick, well developed sheath, whereas the haustoria of the same age in the young host mycelium were devoid of a sheath during early stages of infection. Instead, they were in direct contact with the host protoplast. The incompatible interaction between a resistant host, P. articulosus and the parasite showed similar results as with the old hyphae of C. cucurbitarum. The cell wall of P. articulosus appeared thick-with two or more layers even in the 18-22 h-old hyphae. No contact or interaction was established between the parasite and the non-host L. pennispora. The role of cell wall in the resistance mechanism is discussed.

Cell wall composition regulates cell shape and growth behaviour in pollen tubes

L’une des particularités fondamentales caractérisant les cellules végétales des cellules animales est la présence de la paroi cellulaire entourant le protoplaste. La paroi cellulaire joue un rôle primordial dans (1) la protection du protoplaste, (2) est impliquée dans les mécanismes de filtration et (3) est le lieu de maintes réactions biochimiques nécessaires à la régulation du métabolisme et des propriétés mécaniques de la cellule. Les propriétés locales d’élasticité, d’extensibilité, de plasticité et de dureté des composants pariétaux déterminent la géométrie et la forme des cellules lors des processus de différentiation et de morphogenèse. Le but de ma thèse est de comprendre les rôles que jouent les différents composants pariétaux dans le modelage de la géométrie et le contrôle de la croissance des cellules végétales. Pour atteindre cet objectif, le modèle cellulaire sur lequel je me suis basé est le tube pollinique ou gamétophyte mâle. Le tube pollinique est une protubérance cellulaire qui se forme à partir du grain de pollen à la suite de son contact avec le stigmate. Sa fonction est la livraison des cellules spermatiques à l’ovaire pour effectuer la double fécondation. Le tube pollinique est une cellule à croissance apicale, caractérisée par la simple composition de sa paroi et par sa vitesse de croissance qui est la plus rapide du règne végétal. Ces propriétés uniques font du tube pollinique le modèle idéal pour l’étude des effets à courts termes du stress sur la croissance et le métabolisme cellulaire ainsi que sur les propriétés mécaniques de la paroi. La paroi du tube pollinique est composée de trois composantes polysaccharidiques : pectines, cellulose et callose et d’une multitude de protéines. Pour comprendre les effets que jouent ces différents composants dans la régulation de la croissance du tube pollinique, j’ai étudié les effets de mutations, de traitements enzymatiques, de l’hyper-gravité et de la gravité omni-directionnelle sur la paroi du tube pollinique. En utilisant des méthodes de modélisation mathématiques combinées à de la biologie moléculaire et de la microscopie à fluorescence et électronique à haute résolution, j’ai montré que (1) la régulation de la chimie des pectines est primordiale pour le contrôle du taux de croissance et de la forme du tube et que (2) la cellulose détermine le diamètre du tube pollinique en partie sub-apicale. De plus, j’ai examiné le rôle d’un groupe d’enzymes digestives de pectines exprimées durant le développement du tube pollinique : les pectate lyases. J’ai montré que ces enzymes sont requises lors de l’initiation de la germination du pollen. J’ai notamment directement prouvé que les pectate lyases sont sécrétées par le tube pollinique dans le but de faciliter sa pénétration au travers du style.

Destinée des S-RNases dans les tubes polliniques lors des croisements compatibles et incompatibles

L’auto-incompatibilité (AI) est la capacité génétiquement déterminée d’une plante fertile de rejeter son propre pollen. Chez les Solanacées l’AI dépend des éléments d’un locus fort complexe (locus S) multigénique. L’élément du locus-S exprimé dans le pistil est une ribonucléase (S-RNase) dont le rôle est de dégrader l’ARN chez le pollen self, tandis que l’élément du locus S exprimé dans le pollen est un ensemble de protéines du type F-box, qui sont normalement impliquées dans la dégradation des protéines. Cependant, comment les S-RNases self restent actives lors des croisements incompatibles et comment les S-RNases non-self sont inactivées lors des croisements compatibles ce n’est encore pas clair. Un modèle propose que les S-RNases non-self soient dégradées lors des croisements compatibles. Un autre modèle propose que toutes les S-RNases, self et non-self, soient d'abord séquestrées à l’intérieur d’une vacuole, et elles y resteraient lors des croisements compatibles. Lors de croisements incompatibles, par contre, elles seraient relâchées dans le cytoplasme, où elles pourront exercer leur action cytotoxique. Notre étude tente de répondre à ces questions. Notamment, nous cherchons à mettre en évidence la localisation vacuolaire et/ou cytoplasmique des S-RNases et leur concentration par immunolocalisation, en utilisant un anticorps ciblant la S11-RNase de Solanum chacoense et la microcopie électronique à transmission. Nos résultats montrent que la densité de marquage observée pour les S-RNases cytoplasmiques est significativement plus haute dans les tubes incompatibles que dans ceux compatibles ce qui nous indique que pour qu’un tube pollinique soit compatible il doit contenir une faible densité de S-RNase cytoplasmique.

Ultrastructural analysis of plastids in angiosperm pollen tubes

When Rhododendron pollen tubes are cultured in the dark, electron-dense bodies are present that appear to be a metabolically altered form of a proplastid that is difficult to fix for electron microscopy, and whose membranes may not be intact. When similar pollen tubes are cultured in a dark/light regime, ultrastructurally well-defined proplastids are present after fixation in glutaraldehyde with PIPES buffer and tannic acid, followed by osmic acid. This fixation technique also gave the best ultrastructural images of those proplastids in pollen tubes grown in the dark. Pollen tube plastids have the potential to become chromoplasts when cultured in a dark/light regime as evidenced by the presence of branched tubules characteristic of these organelles. Light appears to be a hitherto neglected environmental factor involved in regulating pollen tube growth. This improved fixation procedure demonstrates the bilayered nature of the membranes surrounding sperm cells and the existence of cytoplasmic channels connecting sperm cell and pollen tube plasma membranes.

Demulsification of water/sunflower oil emulsions by a tangential filtration process using chemically impregnated ceramic tubes

A tangential filtration process was implemented in this study using porous ceramic tubes made of alpha-alumina produced by the slip-casting technique. These tubes were sintered at 1450 degrees C and characterized by mercury intrusion porosimetry, which revealed a mean pore size of 0.5 mu m. The tubes were chemically impregnated with a zirconium citrate solution, after which they were calcined and heat treated at temperatures of up to 600 and 900 degrees C to eliminate volatile organic compounds and transform the zirconium citrate into zirconium oxide impregnated in the alumina in the form of nanoparticle agglomerates. The microporous pipes were tested on a microfiltration hydraulic system to analyze their performance in the demulsification of sunflower oil and water mixtures. The fluid-dynamic parameters of Reynolds number and transmembrane pressure were varied in the process. The volume of permeate was analyzed by measuring the Total Organic Carbon concentration (TOC), which indicated 99% of oil phase retention. The emulsified mixture was characterized by optical microscopy, while the morphology and composition of the impregnated microporous tubes were analyzed by scanning electron microscopy (SEM). Quantification of the TOC values for the tube impregnated once at 600 degrees C showed the best demulsification performance, with the concentration on permeate smaller than 10 mg/L. The impregnated tube sintered once at 900 degrees C presented low carbon concentration (smaller than 20 mg/L), has the advantage of presenting the greatest trans-membrane flux in relation to the other microporous tube. (c) 2006 Elsevier B.V. All rights reserved.

Ultrastructural changes on the epithelial cells of uterine tubes of Wistar rats after chronic ethanol ingestion

The present paper describes the morphological alterations of the epithelial layer of the uterine tubes of rats submitted to experimental chronic alcoholism using anatomical, histological, ultrastructural and morphometric methods. Sixty adult rats (Rattus norvegicus albinus) at the same age (3 months) and with a mean body weight of 228 g were divided into two groups. The control group received solid diet (Purina rat chow) and tap water ad libitum. The alcoholic group received the same solid diet and was allowed to drink only sugar cane brandy dissolved in 30° Gay Lussac (v/v). After periods of 90, 180 and 270 days of treatment animals at normal estrus were anaesthetised with ethyl ether, weighed and sacrificed. Subsequently, the uterine tubes were dissected, weighed and prepared for TEM and SEM methods. The final mean body weights were similar in the control and alcoholic groups. The morphometric analysis showed no difference between control and alcoholic epithelial height. The alcoholic animals showed ultrastructural alterations: intense lipid droplet and lysosomes accumulation, dilated rough endoplasmic reticulum cisternae and vacuolization in both periods of treatment. It was concluded that alcohol acts as a toxin on the epithelial layer of the uterine tubes of rats.

Low-dimensional carbon allotropes: an electron microscopy investigation

The research reported in this manuscript concerns the structural characterization of graphene membranes and single-walled carbon nanotubes (SWCNTs). The experimental investigation was performed using a wide range of transmission electron microscopy (TEM) techniques, from conventional imaging and diffraction, to advanced interferometric methods, like electron holography and Geometric Phase Analysis (GPA), using a low-voltage optical set-up, to reduce radiation damage in the samples. Electron holography was used to successfully measure the mean electrostatic potential of an isolated SWCNT and that of a mono-atomically thin graphene crystal. The high accuracy achieved in the phase determination, made it possible to measure, for the first time, the valence-charge redistribution induced by the lattice curvature in an individual SWCNT. A novel methodology for the 3D reconstruction of the waviness of a 2D crystal membrane has been developed. Unlike other available TEM reconstruction techniques, like tomography, this new one requires processing of just a single HREM micrograph. The modulations of the inter-planar distances in the HREM image are measured using Geometric Phase Analysis, and used to recover the waviness of the crystal. The method was applied to the case of a folded FGC, and a height variation of 0.8 nm of the surface was successfully determined with nanometric lateral resolution. The adhesion of SWCNTs to the surface of graphene was studied, mixing shortened SWCNTs of different chiralities and FGC membranes. The spontaneous atomic match of the two lattices was directly imaged using HREM, and we found that graphene membranes act as tangential nano-sieves, preferentially grafting achiral tubes to their surface.

CO2-driven ocean acidification alters and weakens integrity of the calcareous tubes produced by the serpulid tubeworm, Hydroides elegans

As a consequence of anthropogenic CO2-driven ocean acidification (OA), coastal waters are becoming increasingly challenging for calcifiers due to reductions in saturation states of calcium carbonate (CaCO3) minerals. The response of calcification rate is one of the most frequently investigated symptoms of OA. However, OA may also result in poor quality calcareous products through impaired calcification processes despite there being no observed change in calcification rate. The mineralogy and ultrastructure of the calcareous products under OA conditions may be altered, resulting in changes to the mechanical properties of calcified structures. Here, the warm water biofouling tubeworm, Hydroides elegans, was reared from larva to early juvenile stage at the aragonite saturation state (Omega A) for the current pCO2 level (ambient) and those predicted for the years 2050, 2100 and 2300. Composition, ultrastructure and mechanical strength of the calcareous tubes produced by those early juvenile tubeworms were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and nanoindentation. Juvenile tubes were composed primarily of the highly soluble CaCO3 mineral form, aragonite. Tubes produced in seawater with aragonite saturation states near or below one had significantly higher proportions of the crystalline precursor, amorphous calcium carbonate (ACC) and the calcite/aragonite ratio dramatically increased. These alterations in tube mineralogy resulted in a holistic deterioration of the tube hardness and elasticity. Thus, in conditions where Omega A is near or below one, the aragonite-producing juvenile tubeworms may no longer be able to maintain the integrity of their calcification products, and may result in reduced survivorship due to the weakened tube protection.

Actin-Bundling Protein Isolated from Pollen Tubes of Lily : Biochemical and Immunocytochemical Characterization

A 135-kD actin-bundling protein was purified from pollen tubes of lily (Lilium longiflorum) using its affinity to F-actin. From a crude extract of the pollen tubes, this protein was coprecipitated with exogenously added F-actin and then dissociated from F-actin by treating it with high-ionic-strength solution. The protein was further purified sequentially by chromatography on a hydroxylapatite column, a gel-filtration column, and a diethylaminoethyl-cellulose ion-exchange column. In the present study, this protein is tentatively referred to as P-135-ABP (Plant 135-kD Actin-Bundling Protein). By the elution position from a gel-filtration column, we estimated the native molecular mass of purified P-135-ABP to be 260 kD, indicating that it existed in a dimeric form under physiological conditions. This protein bound to and bundled F-actin prepared from chicken breast muscle in a Ca2+-independent manner. The binding of 135-P-ABP to actin was saturated at an approximate stoichiometry of 26 actin monomers to 1 dimer of P-135-ABP. By transmission electron microscopy of thin sections, we observed cross-bridges between F-actins with a longitudinal periodicity of 31 nm. Immunofluorescence microscopy using rhodamine-phalloidin and antibodies against the 135-kD polypeptide showed that P-135-ABP was colocalized with bundles of actin filaments in lily pollen tubes, leading us to conclude that it is the factor responsible for bundling the filaments.

Theory of electron driven shock waves

"STL/TR-60-0000-GR310."