The diet and gastrodermal ultrastructure of polystomatid monogeneans infecting chelonians

Parasitology ◽  
1989 ◽  
Vol 98 (2) ◽  
pp. 265-273 ◽  
Author(s):  
K. M. Allen ◽  
R. C. Tinsley
Keyword(s):  
Epithelial Cells ◽  
Blood Feeding ◽  
Intracellular Accumulation ◽  
X Ray ◽  
Intracellular Digestion ◽  
Transmission Electron ◽  
Supportive Role ◽  
Histochemical Tests ◽  
High Concentrations ◽  
Host Blood

SUMMARYAll polyopisthocotylean monogeneans previously studied, including representatives of the Polystomatidae infecting anuran amphibians, feed on host blood. However, the present analysis of species of Polystomoides, Polystomoidella and Neopolystoma, polystomatids which infect chelonian reptiles, has shown that this group has diverged nutritionally from related parasites. Histochemical tests failed to demonstrate haemoglobin in the gut caeca, and X-ray microanalysis confirmed the absence of haematin (or high concentrations of bound iron) in the gastrodermis. The chelonian poly-stomatids (and also the single monogenean which infects a mammal, Oculotrema hippopotami) feed on epithelial cells and mucus, the diet typical of monopisthocotyleans. Transmission electron microscopy revealed the same gastrodermal architecture in representatives of Polystomoides from Africa, N. America and S.E. Asia. The organization of the caecal epithelium conforms with that of blood-feeding polyopisthocotyleans, with two components: lamellated cells responsible for intracellular digestion interspersed with elements of a non-lamellated connecting syncytium. In other polyopistho-cotyleans, the syncytium probably has a skeletal, supportive role, related to the problems of intracellular accumulation of haematin, but in polystomatids infecting chelonians the syncytium is extremely reduced and its presence probably reflects an ancestry amongst blood-feeding relatives. The utilization of the presumably more primitive monogenean diet of epithelial cells and mucus by chelonian polystomatids may be related to the scarcity of superficial blood vessels in their oral and urinary bladder habitats.

Abundance of halloysite neoformation in soils developed from crystalline rocks. Contribution of transmission electron microscopy

Clay Minerals ◽  
1992 ◽  
Vol 27 (1) ◽  
pp. 35-46 ◽  
Author(s):  
R. Romero ◽  
M. Robert ◽  
F. Elsass ◽  
C. Garcia
Keyword(s):  
Thermal Analyses ◽  
Crystalline Rocks ◽  
Metamorphic Rocks ◽  
X Ray Diffraction ◽  
Nw Spain ◽  
X Ray ◽  
Transmission Electron ◽  
High Concentrations ◽  
Bioclimatic Conditions ◽  
Mineralogical Phases

AbstractThe soils developed from crystalline and metamorphic rocks in Galicia (NW Spain), are characterized by high concentrations of 1 : 1 phyllosilicates and gels. Thermal analyses, X-ray diffraction after formamide treatment, and IR spectroscopy in the OH vibration range have been performed on the clay fractions, but do not discriminate clearly between the different associated mineralogical phases. HRTEM studies linked with microdiffraction and microanalyses have led to the identification of several types of gel which transform into goethite, gibbsite, clay precursors, and/ or halloysite according to their composition (Fe, Al or Si-Al). Halloysite-like minerals are the main constituents and they have a great variety of morphologies: lamellar, spheroidal, tubular, platy or poikilitic. In general, halloysite and gel formation on crystalline rocks is related to the bioclimatic conditions, involving high hydrolysis in the presence of organic matter. This halloysite seems to be a metastable mineral which would evolve into kaolinite with increasing weathering time.

scholarly journals The Influences of Magnesium upon Calcium Phosphate Mineral Formation and Structure as Monitored by X-ray and Vibrational Spectroscopy

Soil Systems ◽  
2020 ◽  
Vol 4 (1) ◽  
pp. 8
Author(s):  
David M. Hilger ◽  
Jordan G. Hamilton ◽  
Derek Peak
Keyword(s):  
Calcium Phosphate ◽  
Calcareous Soils ◽  
X Ray Diffraction ◽  
Edge Structure ◽  
X Ray ◽  
Transmission Electron ◽  
Phosphate Mineral ◽  
Local Bonding ◽  
Wide Range ◽  
High Concentrations

Calcium phosphate minerals are typically the solubility-limiting phase for phosphate in calcareous soils. Magnesium (Mg), despite being present in high concentrations in calcareous soils, has been largely neglected in the study of formation and stabilization of soil phosphate minerals due to the high solubility of pure Mg phosphate phases. In this study, a series of four common calcium and magnesium phosphate minerals, hydroxyapatite/bobierrite and brushite/newberyite were synthesized in the presence of widely varying Mg concentrations to examine the effects of Mg substitution upon the local bonding environment and overall structure of the precipitates. Phosphorus K-edge X-Ray absorption near edge structure (XANES) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) provide insight into the local coordination environment, whereas synchrotron powder X-Ray diffraction (SP-XRD) and transmission electron microscopy (TEM) were used for structural analysis. In acidic to neutral pH, Mg-bearing brushite phases formed over a wide range of Ca:Mg ratios. In neutral to high pH systems, a short-range order amorphous calcium phosphate (ACP) with a local structure analogous with hydroxyapatite precipitated for a wide range of Ca to Mg ratios. It can be inferred that the presence of Mg in soils leads to stabilization of metastable phases: via cation substitution in brushite and via poisoning of crystal growth propagation for hydroxyapatite.

Parallel-EELS mapping of calcium in cryosectioned cells

1992 ◽  
Vol 50 (2) ◽  
pp. 1566-1567
Author(s):  
R.D. Leapman ◽  
J.A. Hunt ◽  
R.A. Buchanan ◽  
S.B. Andrews
Keyword(s):  
High Sensitivity ◽  
Scanning Transmission Electron Microscope ◽  
Mineralized Tissue ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Spectrum Imaging ◽  
High Concentrations ◽  
Electron Energy Loss ◽  
Better Than

Electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) provides a high sensitivity for microanalysis of certain important biological elements whose physiological concentrations in cells are rather low. Minimum detectable concentrations for calcium obtained by EELS can be better than those obtained by energy-dispersive x-ray spectroscopy (EDXS). However, in order to detect the very small core-edge signal/background ratios encountered in EELS of biological specimens, relatively elaborate acquisition and processing methods must be employed. Application of another strategy, STEM-EELS elemental mapping, has generally been restricted to analyses where elements are present at relatively high concentrations, such as calcium in mineralized tissue or carbon, nitrogen and oxygen in organic specimens.This is because only simple methods were available for signal estimation if the data had to be processed on-the-fly. Recently there has been considerable interest in the spectrum-imaging technique where entire spectra are collected at each pixel. In the present work we have applied this technique to measure calcium in Purkinje cell dendrites of rapidly frozen mouse cerebellar cortex.

Structure and Composition of Luminescent Laterally Anodized Porous Si

1991 ◽  
Vol 256 ◽  
Author(s):  
K. H. Jung ◽  
S. Shih ◽  
T. Y. Hsieh ◽  
J. C. Campbell ◽  
D. L. Kwong ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Lower Layer ◽  
Amorphous Layer ◽  
Porous Si ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
High Concentrations ◽  
Secondary Ion ◽  
Very High

ABSTRACTWe have made structural and compositional studies of luminescent laterally anodized porous Si. Scanning electron microscopy reveals a surface with a network of cracks, while transmission electron microscopy shows a dual porous Si structure in which the upper layer is amorphous and the lower layer is either amorphous or crystalline, depending on anodization conditions. X-ray diffraction verified the presence of the amorphous layer. Secondary ion mass spectroscopy reveals very high concentrations of H, B, C, N, O, and F in the amorphous layer. Our results indirectly suggest that the amorphous layer is primarily responsible for luminescence.

Ultrastructure and X-ray analysis of phosphorus granules in a vesicular–arbuscular mycorrhizal fungus

1979 ◽  
Vol 57 (24) ◽  
pp. 2812-2818 ◽  
Author(s):  
J. A. White ◽  
M. F. Brown
Keyword(s):  
Arbuscular Mycorrhizal Fungus ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
X Ray ◽  
Dense Granules ◽  
Transmission Electron ◽  
Cellular Inclusions ◽  
Vesicular Arbuscular ◽  
Probable Site ◽  
High Concentrations

The vesicular–arbuscular mycorrhizal fungus Glomus mosseae was examined by transmission electron microscopy and energy dispersive X-ray analysis. Electron-dense granules, found within vacuoles, were analyzed by X-ray analysis and found to contain high concentrations of phosphorus and calcium. These granules were similar in appearance to the polyphosphate granules described in other organisms. Highly vacuolated intercellular hyphae and vesicles possessed the greatest number of phosphorus granules. The granules were present in vacuolated arbuscular hyphae but absent from completely collapsed arbuscules. It was determined that the active arbuscule was the most probable site of breakdown of phosphorus granules. There were two other types of cellular inclusions, one vacuolar and one cytoplasmic, that could not be identified by X-ray analysis but that could easily be mistaken for phosphorus granules. It was concluded that general morphological appearance and location were not adequate criteria for the identification of phosphorus granules.

scholarly journals Treatment of Alkaline Cr(VI)-Contaminated Leachate with an Alkaliphilic Metal-Reducing Bacterium

2015 ◽  
Vol 81 (16) ◽  
pp. 5511-5518 ◽  
Author(s):  
Mathew P. Watts ◽  
Tatiana V. Khijniak ◽  
Christopher Boothman ◽  
Jonathan R. Lloyd
Keyword(s):  
Photoelectron Spectroscopy ◽  
Bacterial Cells ◽  
Chromite Ore Processing Residue ◽  
Content Type ◽  
X Ray ◽  
Transmission Electron ◽  
Ore Processing ◽  
Alkaline Environments ◽  
Alkaline Conditions ◽  
High Concentrations

ABSTRACTChromium in its toxic Cr(VI) valence state is a common contaminant particularly associated with alkaline environments. A well-publicized case of this occurred in Glasgow, United Kingdom, where poorly controlled disposal of a cementitious industrial by-product, chromite ore processing residue (COPR), has resulted in extensive contamination by Cr(VI)-contaminated alkaline leachates. In the search for viable bioremediation treatments for Cr(VI), a variety of bacteria that are capable of reduction of the toxic and highly soluble Cr(VI) to the relatively nontoxic and less mobile Cr(III) oxidation state, predominantly under circumneutral pH conditions, have been isolated. Recently, however, alkaliphilic bacteria that have the potential to reduce Cr(VI) under alkaline conditions have been identified. This study focuses on the application of a metal-reducing bacterium to the remediation of alkaline Cr(VI)-contaminated leachates from COPR. This bacterium, belonging to theHalomonasgenus, was found to exhibit growth concomitant to Cr(VI) reduction under alkaline conditions (pH 10). Bacterial cells were able to rapidly remove high concentrations of aqueous Cr(VI) (2.5 mM) under anaerobic conditions, up to a starting pH of 11. Cr(VI) reduction rates were controlled by pH, with slower removal observed at pH 11, compared to pH 10, while no removal was observed at pH 12. The reduction of aqueous Cr(VI) resulted in the precipitation of Cr(III) biominerals, which were characterized using transmission electron microscopy and energy-dispersive X-ray analysis (TEM-EDX) and X-ray photoelectron spectroscopy (XPS). The effectiveness of this haloalkaliphilic bacterium for Cr(VI) reduction at high pH suggests potential for its use as anin situtreatment of COPR and other alkaline Cr(VI)-contaminated environments.

scholarly journals COPPER HEXACYANOFERRATE (II): SYNTHESIS, CHARACTERIZATION, AND CESIUM, STRONTIUM ADSORBENT APPLICATION

2021 ◽  
Author(s):  
Dinh Trung Nguyen ◽  
Vu Tram Anh Le ◽  
Dong Phuong Truong ◽  
Thi Dan Thy Kieu ◽  
Tran Thuy Hong Nguyen ◽  
...  
Keyword(s):  
Low Cost ◽  
Bet Surface Area ◽  
Precipitation Method ◽  
Maximum Adsorption Capacity ◽  
X Ray Diffraction ◽  
Copper Hexacyanoferrate ◽  
X Ray ◽  
Transmission Electron ◽  
High Concentrations ◽  
Co Precipitation

Low-cost nanoscale copper hexacyanoferrate (CuHF), a good selective adsorbent for cesium (Cs+) removal, was prepared using the chemical co-precipitation method. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and high-resolution transmission electron microscopy (HR-TEM) were conducted to determine the CuHF morphology. Copper hexacyanoferrate, Cu13[Fe(CN)6]14.(2K).10H2O, has a cubic structure (space group F-43m) in the range of 10-30 nm and a Brunauer-Emmett-Teller (BET) surface area of 462.42 m2/g. The removal of Cs+ and Sr2+ is dependent on pH; the maximum adsorption capacity (qmax) of CuHF is achieved at a pH = 6. From the Langmuir model, qmax = 143.95 mg/g for Cs+ and 79.26 mg/g for Sr2+, respectively. At high concentrations, Na+, Ca2+, and K+ ions have very little effect on Cs+ removal, and Na+ and K+ ions have a higher affinity for removing Sr2+ than Ca2+ at all concentrations. CuHF has a high affinity for alkaline cations in the order: Cs+ > K+ > Na+ > Ca2+ > Sr2+, as proposed and discussed.

Quantitative EELS mapping of biological thin sections

1992 ◽  
Vol 50 (2) ◽  
pp. 1568-1569
Author(s):  
Y.Y. Wang ◽  
Z. Shao ◽  
R. Ho ◽  
A.V. Somlyo ◽  
A.P. Somlyo
Keyword(s):  
Spatial Resolution ◽  
Power Law ◽  
High Spatial Resolution ◽  
Local Composition ◽  
Thin Sections ◽  
X Ray ◽  
Elemental Concentrations ◽  
Transmission Electron ◽  
High Concentrations ◽  
Electron Energy Loss

X-ray microanalysis and electron energy loss spectroscopy are reliable methods for determining at high spatial resolution the local composition of biological materials. EELS imaging, although potentially more sensitive than X-ray analysis, is complicated by the large background of EELS spectra. The conventional power law fitting of the EELS background can only be used for analysis of high concentrations and/or very thin sections (t< 0.3 λ) and it is not reliable for mapping low elemental concentrations. For the detection of low elemental concentrations at high spatial resolution, the background subtraction of the EELS spectrum and correction of long term microscope drift are critical, and limit the use of conventional energy filtered transmission electron microscopy. Therefore, we used energy filtered STEM with multiple least squares fitting, including the plural plasmon contribution to the background, to obtain quantitative phosphorus (P) and calcium (Ca) concentration maps of cryosections.The failure of the power law is due to the plural scattering contributions to the Background.

Imperfections in type I and type II diamonds

1962 ◽  
Vol 270 (1343) ◽  
pp. 538-552 ◽  
Keyword(s):  
Ultra Violet ◽  
Type I ◽  
Type Ii ◽  
Dislocation Loops ◽  
Screw Dislocations ◽  
X Ray ◽  
Transmission Electron ◽  
Infra Red ◽  
High Concentrations ◽  
Absorption Measurements

Natural diamonds have been thinned sufficiently by oxidation at 750 °C in oxygen or at 1350 °C in carbon dioxide for examination by transmission electron microscopy. Type I and type II diamonds as classified by infra-red and ultra-violet absorption measurements have been investigated and a difference in the nature of the imperfections in the two types has been found. Impurity platelets are present on {100} planes in type I diamonds and the relevant impurity has been identified as most probably nitrogen, since the density of platelets can be explained only by the high concentrations of nitrogen found in such diamonds by other workers. The presence of the nitrogen in platelet form can explain anomalous X-ray spikes reported around the normal Laue spots and also the fact that the nitrogen has been found to be present in a non-paramagnetic form. Small dislocation loops have been revealed on {111} planes near the nitrogen platelets and have been attributed to the condensation of vacancies following the formation of the platelets. Both these types of imperfection are absent in type II diamonds. Defects common to both types are dislocations and also long narrow dislocation dipoles which are considered to be formed by the movement of screw dislocations containing long jogs through the crystal at high temperatures. It is suggested that type II diamonds may have grown in nitrogen-free conditions at temperatures similar to those required for type I diamonds and have cooled slowly or they may have grown at lower temperatures than type I diamonds.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

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