Re-Exposure of Tapes at High Temperature and Pressure in the Lycopodium Clavatum Spore Exine

Lamellations are visualizable through the staining commonly used in transmission electron microscopy during exine formation on Lycopodium and other spores, and the nexine of pollen grains. The lamellations so exposed consist-of dark tapes at either side of an unstained (white) line. Neither tapes nor white lines are visualizable in the exine of mature spores of Lycopodium. The continued presence of lamellations having tape-white line spacing has been demonstrated with inorganic tracers in the nexine of pollen in which lamellations otherwise appeared to be absent. Through high contrast staining methods for TEM we have observed lamellations in the residual exine following heat treatment (350[ddot]C) of mature spores of Lycopodium clavatum. The surface of these residual exines was etched by treatment with hot 2-aminoethanol and filaments were observed to protrude from the etched surfaces. The residual exine stained darkly. Lycopodium spores heated to 300[ddot]C at 1 kb pressure had long filaments exposed at the surface of the residual exine (sporopollenin). Sections of the pellet remaining after heat and pressure treatment also included bundles of closely parallel filaments and masses of isolated filaments. The filaments were stained while the exine residue, assumed to include sporopollenin, was not. Isolated filaments produce a stable metachromasia with toluidine blue indicating the presence of many closely spaced sites of negative charge. The staining of intact exines with basic dyes may result from anionic sites on filaments embedded within the exine rather than being due to sporopollenin. The results of our experiments indicate that the filaments are more resistant to heat and pressure and 2-aminoethanol than is sporopollenin. We propose that the trilamellar elements commonly called tapes and white lines might be composed of two filaments bridged by polybasic molecules.     

Morphometric analyses of the electric organ of Torpedo: The influence of different fixative modes on the vesicle diameter

Summary The influences of various fixatives on the vesicle size of the electric organ of Torpedo marmorate were investigated. Thin section and freeze etched preparations were examined under the electron microscope.In thin section increased vesicle diameters were observed compared with the freeze etched preparations. The same experiments in different torpedo fish led to significantly different vesicle sizes observed. Variations of the molarity, the pH and osmolarities result in particularly high differences in vesicle diameters.Using Karnovsky's method (1965) and a fixative consisting of 2.5% glutaraldehyde in 0.2 M cacodylate buffer, pH 7.2, results in vesicle sizes comparable to those reported by other authors.Results obtained from freeze etched preparations are not comparable in general with results from thin section experiments with the same fixative.     

Shear bond strength between different materials bonded with two resin cements

doi: 10.1111/j.1741‐2358.2011.00565.x
Shear bond strength between different materials bonded with two resin cements Background: The aim of this study was to compare the shear bond strength between Ni–Cr alloy specimens bonded to air‐abraded Ni–Cr, bur‐abraded Ni–Cr, etched ceramic and etched enamel substrates using the resin cements RelyX ARC or Enforce. Materials and methods: Ni–Cr specimens were made and sandblasted with Al₂O₃ airborne‐particles. Disc‐shaped patterns were made for each of the four experimental substrates: Ni–Cr treated with Al₂O₃ airborne‐particles, Ni–Cr treated with diamond bur abrasion, etched enamel and etched ceramic. Results: Significant differences in shear bond strength were found between the different materials and luting agents evaluated. The Ni–Cr alloy cylinders bonded to Ni–Cr surfaces sandblasted with 50 μm Al₂O₃ particles and bonded with Enforce achieved the highest bond strength when compared with other substrates (28.9 MPa, p < 0.05). Bur‐abraded metal discs had lowest values, regardless the cement used (2.9 and 6.9 MPa for RelyX and Enforce, respectively). Etched enamel and etched ceramic had similar shear bond strengths within cement groups and performed better when RelyX was used. Conclusions: Bonding Ni–Cr to Ni–Cr and ceramic may result in similar and higher bond strength when compared to Ni–Cr/enamel bonding. For metal/metal bonding, higher shear bond strength was achieved with resin cement Enforce, and for metal/ceramic and metal/enamel bonding, RelyX had higher results.     

Electron-microscopic study of the collagen fibrils of the rat tail tendon as revealed by freeze-fracture and freeze-etching techniques

Summary The ultrastructure of the collagen of rat tail tendon was investigated by the freeze-fracture technique. Collagen fibers were pretreated with the digestive enzymes, -amylase, elastase and collagenase to remove matrix substances. Some of the samples were etched for 20 min. Fibrils had an average diameter of 318±12 nm and a banded structure with a mean periodicity of 64.2±0.9 mm; the banding was most marked in -amylase/elastase-treated specimens, although the periodicity was independent of pretreatment. Microfibrils were well-displayed following -amylase/elastase and collagenase pretreatments. A difference in the diameters of microfibrils was, however, observed between etched specimens (8.3±0.3 nm) and those prepared by other experimental methods (11.4±0.5 nm). In replicas of collagenase-treated and etched specimens, the interconnecting filaments in the interfibrillar region formed a network that was continuous with the microfibrils of collagen fibrils. The diameter of the interconnecting filaments was the same as that of microfibrils. Microfibrillar bundles were observed in the interfibrillar region.     

Effect of Support Material on the Development of Microbial Fixed Films Converting Acetic Acid to Methane*

A study of the development of methanogenic fixed films on pieces of polyvinyl chloride plastic, etched glass and baked clay showed that support material markedly affected the rate of attachment and growth of bacteria converting acetic acid to methane. Film development, as indicated by the rate of acetate conversion to methane and carbon dioxide, was threefold faster on fired clay than on either PVC plastic or etched glass. Scanning electron micrographs showed that the film of bacteria attached to clay was thick and uniform, while the film attached to PVC plastic was thin although still uniform. Attachment to etched glass was spotty. The characteristics of clay which made it a superior support appeared to be its rough, porous surface which offered attachment sites to the micro-organisms and the presence of minerals in the clay, particularly iron which is known to stimulate methanogenesis and growth.     

Johnsongrass Chlorotic Stripe Mosaic and its Associated Viruslike Particles in Iran1

A mosaic disease of Johnsongrass characterized by the presence of short and long chlorotic stripes in leaves and stunting of plants was found in two locations about 300 km apart in the Fars Province of Iran. The disease occurred in patches or along the irrigation ditches. The disease agent could not be transmitted mechanically or by certain insects and mites. About 0.5% of the seedlings, grown in soil from the root zone of diseased plants, developed the disease after 1–8 months. Electron microscopy, of leaf-dip preparations showed presence of isometric viruslike particles (VLPs) of about 35 nm diameter in unusually high concentrations in diseased plants but not in healthy plants. VLPs from diseased leaves were purified by low-pH clarification followed by differential and densitygradient centrifugation. Purified VLP preparations showed UV absorption spectrum typical of nucleoproteins. A260/A280 was 1.48. High titered antisera obtained by injecting rabbits with purified VLPs reacted with sap from diseased plants but not healthy plants. Purified VLP preparations and sap from diseased plants did not react with antisera to Bermuda grass etched line, Brachypodium sylvaticum, brome mosaic, maize chlorotic dwarf, maize rayado fino, maize white line mosaic and tobacco necrosis viruses.     

Differences in colonisation of five marine bacteria on two types of glass surfaces

The retention patterns of five taxonomically different marine bacteria after attachment on two types of glass surfaces, as-received and chemically etched, have been investigated. Contact angle measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray fluorescence spectroscopy (XRF) and X-ray photoelectron spectrometry (XPS) were employed to investigate the impact of nanometer scale surface roughness on bacterial attachment. Chemical modification of glass surfaces resulted in a ～1 nm decrease in the average surface roughness (R _a) and the root-mean-squared roughness (R_q ) and in a ～8 nm decrease in the surface height and the peak-to-peak (R _max) and the 10-point average roughness (R_z ). The study revealed amplified bacterial attachment on the chemically etched, nano-smoother glass surfaces. This was a consistent response, notwithstanding the taxonomic affiliation of the selected bacteria. Enhanced bacterial attachment was accompanied by elevated levels of secreted extracellular polymeric substances (EPS). An expected correlation between cell surface wettability and the density of the bacterial attachment on both types of glass surfaces was also reported, while no correlation could be established between cell surface charge and the bacterial retention pattern.     

Tactile Detection Thresholds for a Single Asperity on an Otherwise Smooth Surface

An investigation was made of the capacities of humans to detect, by actively touching with the fingertip, the presence of a single, small asperity on a very smooth background. The asperity consisted of either a raised dot having a diameter of 602, 231, or 40 μum, or an edge, each etched into a silicon wafer using the methods of contact photolithography. The height of each dot or edge was varied and the subject was asked to make a forced choice on each test trial as to which of two wafers, one of which was blank, contained the asperity. The mean detection threshold, or minimal height of asperity corresponding to a d' of 1.35, was lowest for edges (0.85 ± 0.22 μm, SD) and increased with decreases in the diameter of dot from 1.09 ± 0.19 μm for a diameter of 602 μm to 2.94 ± 1.19 μm and 5.97 ± 2.02 μm for diameters of 231 μm and 40 μm, respectively. The type of skin displacement required for the detection of these small asperities was believed to be a local lateral deformation of the papillary ridges.     

Bacterial attachment on optical fibre surfaces

Optical fibres have received considerable attention as high-density sensor arrays suitable for both in vitro and in vivo measurements of biomolecules and biological processes in living organisms and/or nano-environments. The fibre surface was chemically modified by exposure to a selective etchant that preferentially erodes the fibre cores relative to the surrounding cladding material, thus producing a regular pattern of cylindrical wells of approximately 2.5 μm in diameter and 2.5 μm deep. The surface hydrophobicity of the etched and non-etched optical fibres was analysed using the sessile pico-drop method. The surface topography was characterised by atomic force microscopy (AFM), while the surface chemistry was probed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Six taxonomically different bacterial strains showed a consistent preference for attachment to the nano-scale smoother (R _q = 273 nm), non-etched fibre surfaces (water contact angle, θ = 106° ± 4°). In comparison, the surfaces of the etched optical fibres (water contact angle, θ = 96° ± 10°) were not found to be amenable to bacterial attachment. Bacterial attachment on the non-etched optical fibre substrata varied among different strains.     

Er,Cr:YSGG激光切割对牙体与充填物粘结力影响的研究

本文用 1千牛电液疲劳实验机检测充填材料与牙面之间的粘结力 ,发现 :在牙釉质组中 ,酸蚀组、6瓦激光切割组及 6瓦激光切割联合酸蚀组抗剪切粘结强度无显著性差异 (P >0 .0 5) ;在牙本质组中 ,酸蚀组、4瓦激光切割组及 4瓦激光切割联合酸蚀组抗剪切粘结强度也无显著性差异 (P >0 .0 5)。并通过SEM观察激光处理后牙体表面结构的变化 ,发现激光切割后牙釉质表面不平呈层状 ,无玷污层 ,釉柱未见破坏 ;牙本质小管开放 ,表面无玷污层 ,达到酸蚀的效果。因此Er,Cr :YSGG激光切割牙体硬组织具有传统钻切割与酸蚀刻的联合作用 ,可以代替传统的酸蚀方法。     

Further Studies on the Organization of the Paraxial Rod of Trypanosomatids1

ABSTRACT. The fine structure of the paraxial rod of Phytomonas davidi and Herpetomonas megaseliae was analyzed in thin sections of Triton X-100-extracted, tannic acid-glutaraldehyde-fixed cells and in replicas of quick-frozen, freeze-fractured, deeply etched and rotary shadowed cells. The paraxial rod is formed by a complex array of filaments. Two regions, designated as proximal and distal, are formed by two and at least 11 plates, respectively, composed of an association of 25-nm and 7.0-nm-thick filaments which are oriented at an angle of-50° in relation to the major axis of the axoneme. The intermediate region is less dense and is formed by thin filaments. Short single and Y-shaped filaments connect the proximal plate to doublets numbers 4 and 7 of the axoneme. Based on the images obtained in stereopairs as well as in photographs obtained before and after inclination of the specimen, a three-dimensional model of the paraxial rod is proposed.     

Ultrastructure of the capsule of Klebsiella pneumoniae and slime of Enterobacter aerogenes revealed by freeze etching

Summary The capsule of Klebsiella pneumoniae type I and slime of Enterobacter aerogenes strain A3 (SL) was examined by electron microscopy using the freeze etch technique. The capsules of K. pneumoniae were found to be composed of several layers of polysaccharide 10 nm thick; while the polysaccharide slime of E. aerogenes strain A3 (SL) was found to be composed of a diffuse network of fibrils. This work represents the first effort to visualize the replica of the unfixed, partially hydrated bacterial capsule or slime in the electron microscope. The slime of E. aerogenes strain A3 (SL) which was purified, and then freeze etched, resembled the layered structure of the capsule of K. pneumoniae. It is suggested that the charge or dielectric constant of the slime polysaccharide polymers was altered during purification, thereby permitting the layering to occur.Paper presented at the Annual Meeting of the American Society for Microbiology, Philadelphia, Pa. (U.S.A.), 1972.     

Accuracy and precision of age determination using growth layer groups for California sea lions (Zalophus californianus) with known ages

Age determination from counts of growth layer groups (GLGs) in tooth dentine is a common method for aging marine mammals. Using known‐aged animals, we validated this method for acid etched teeth of California sea lions (CSLs), Zalophus californianus. Between 1991 and 2013, the upper left canine (n = 33) was collected opportunistically during necropsy from animals tagged or branded as pups that later died. Overall, 55%–61% of age estimates by GLG counting were within 1 yr of the known‐age in the sample of 1–30‐yr‐old CSLs. Accuracy of age estimates was found to be dependent on age of the CSLs, however. 71%–79% of age estimates were within 1 yr of the known‐age in CSLs <10 yr old. These findings support the validity of counting GLGs to estimate age for CSLs <10 yr old to within 1 yr of accuracy.     

The effect of oxygen and humidity on charged particle registration in organic foils

The number and diameter of microscopically visible alpha-particle tracks which can be etched in the surface of sensitive plastic foils such as cellulose triacetate are increased by the presence of oxygen. Pre- or posttreatment of foils with water or humid air increases the etching speed but not the foils' sensitivity. Treatment of foils with diluted H202 increases the sensitivity slightly, but the etching speed considerably. Some parameters of the oxygen/humidity effect are described; its possible consequences for the interpretation of the latent track formation process and its practical applications are discussed briefly.     

Polyclonal Antibodies to the Coat Protein of Carnation etched ring virus Expressed in Bacterial System: Production and Use in Immunodiagnosis†

Carnation etched ring virus (CERV), is the most widespread virus in carnation cultivars after Carnation mottle virus. It's incidences has been reported worldwide. It has double stranded DNA genome with the length of ∼8 kbp. Primers were designed for CERV coat protein gene (1482 bp) amplification and directional and inframe cloning in expression vector, pET‐28a(+) (Novagen, USA), using Escherichia coli strain BL 21 strain competent cells. Expression conditions for maximum recovery of soluble recombinant protein was standardized. The in vitro expressed protein was purified and was used as an antigen for raising antisera. Both intramuscular and sub‐cutaneous routes were used separately for antisera production and the antisera was purified. Some of the antisera was used for enzyme conjugate preparation. This antiserum and conjugate were then used for formulation of an ELISA‐based diagnostic kit for CERV detection. Its properties were compared with the commercially available kit. In all cases, with both glasshouse and field material, the antibodies had good detectability and specificity. These antibodies combine specificity to the target protein and versatility with regard to all the more important serological techniques.     

The pigment ofPseudomonas paucimobilis is a carotenoid (Nostoxanthin), rather than a brominated aryl-polyene (xanthomonadin)

Metal ions and their hydroxide or oxide hydrate derivatives interact with the complex polyanionic network of the cell wall and this has drastic effects on the dimensions of the structure. The measured thickness of the wall ofBacillus subtilis (strain Marburg 168) ranged from 16 to 30 nm according to the metal salt used to give contrast. The reactivity of the wall was modified by blocking or altering available reactive groups—e.g., amine, hydroxyl, and carboxyl—and by varying the fixative used. The most significant dimensional changes involved carboxyl modification. The best reference preparations for judging thickness were considered to be replicas of freeze-cleaved and etched specimens, which gave a minimum thickness of 27 nm.     

Detection and quantification of ATP and heavy metal with electronical micro-circuits

In order to use whole eukaryotic cells as an active element in the detection and amplification of biological signals, for both in vitro and in vivo applications, we have undertaken a first approach to interface live cells and integrated circuit, and evaluate the possibility to develop a microbioreactor. An amplified photodiode system was designed and built as an electronical circuit in a way that it could easily be miniaturised. In parallel micro-chips with silicium chambers were used as microbioreactors to adhere cells. We showed here that this etched silicon chamber allows endothelial and CHO cells spreading, permitting determination of a number of cell properties {\it on line} providing appropriate integrated circuits are designed to perform the desired functions. The photodiode system reacting to the luminescent luciferase system permitted, through the use of appropriate software from a personal computer (PC) connected on line in vitro, the determination of ATP concentration, and using different luciferase transfected bacteria permitted the detection of constitutive or induced luminescence. This revised version was published online in July 2006 with corrections to the Cover Date.     

Biosorption of trivalent and hexavalent chromium from aqueous systems using shelled Moringa oleifera seeds

Abstract

The present study explores the sorption properties of shelled Moringa oleifera seeds (SMOS) for removal of two environmentally important oxidation states of chromium (trivalent and hexavalent) from an aqueous system on the laboratory scale. Sorption studies reveal the optimum conditions for the removal of 81.02%; Cr (III) and 88.15% Cr (VI) as follows: biomass dosage (4.0 g), metal concentration [25mg/L for Cr (III); 50mg/L for Cr (VI)], contact time (40 minutes) at pH 6.5 and 2.5 respectively. The adsorption data were found to fit well both the Freundlich and Langmuir isotherms. Characterization of the seed powder by FTIR showed the clear presence of amino acid moieties having both positively charged amino and negatively charged carboxylic groups and confirmed that biosorption involves amino acid-chromium interactions. SEM studies of native and exhausted [Cr(III) and Cr(VI)] treated SMOS revealed large spherical clusters having a pore area of 8.66 µm² in the case of native SMOS while dense agglomerated etched dendrite type morphology have a pore area of 0.80 µm² in Cr (III) and 0.78 µm² in Cr (VI) treated SMOS The spent biosorbent was regenerated and found to be effectively reusable for four cycles.     

Silurian calcispheres (Calcitarcha) of Gotland (Sweden): Comparisons with calcareous dinoflagellates

Scanning electron microscope examinations of polished and etched surfaces of sediments from the Silurian carbonate platform of Gotland, Sweden, revealed the presence of numerous, morphologically diverse “calcispheres” (Calcitarcha). Some of these spherical calcareous microfossils display wall structures that are surprisingly similar to those of calcareous dinoflagellate cysts. In analogy to the interpretation of the biological affinities of Palaeozoic acritarchs as cysts of organisms that might have been the ancestors of organic-walled dinoflagellates, the Calcitarcha from Gotland can be compared and may possibly be related to organisms that may have been the ancestors of calcareous cyst-producing dinoflagellates that so far have not been observed before the Late Jurassic.     

Histochemistry of glycosaminoglycans in cartilage ground substance

Summary The critical-electrolyte-concentration staining method using Alcian blue (AB) was applied to etched semithin Epon-embedded sections. The distribution of various glycosaminoglycans (GAGs) was studied in hyaline, elastic, cellular and fibrous cartilage obtained from humans and rodents. The staining patterns in semithin sections were found to correspond to those obtained using paraffin-embedded material. Lectin histochemistry was performed on consecutive sections. The following peroxidase-labelled lectins were used: Ricinus communis A I, Arachis hypogaea, Ulex curopaeus A I, Triticum vulgaris, Helix pomatia, Limax flavus, and concanavalin A. The lectin-binding capacity of cartilaginous ground substance was found to be low, as was expected on account of the few free sugar residues of GAGs. Chondroitin sulphate, the most widely distributed GAG, did not exhibit lectin staining. The lectin-binding site (positive staining for all lectins tested except H. pomatia) observed corresponded to areas positive forkeratan sulphate, as shown by AB staining in preceding or following sections. The pronounced lectin binding seen in cellular structures and the inner territorial matrix regions is considered to be due to higher concentrations of oligosaccharides involved in the metabolism of GAGs.Supported by the Hochschuljubiläumsstiftung der Stadt Wien