Light, electron microscopy and histopathology of Myxobolus salminus n. sp., a parasite of Salminus brasiliensis from the Brazilian Pantanal

In this report, we describe the morphology and histopathology of Myxobolus salminus n. sp., a parasite of the gill filaments of wild Salminus brasiliensis (dourado) from the Brazilian Pantanal. The small polysporic plasmodia were similar to 100 mu m in diameter and the development was asynchronous. The mature spores were oval to pear shaped and had a smooth wall. The spore measurements were (mean +/- S.D., with range in parentheses): length 10.1 +/- 0.4 mu m (9.6-10.5), width 6.1 +/- 0.4 mu m (5.8-6.6) and thickness 5.0 +/- 0.6 mu m (4.7-5.3). The polar capsules were elongated and of equal size: length 4.6 +/- 0.2 mu m (4.3-4.8) and width 1.7 +/- 0.1 mu m (1.5-1.9). The histological analysis revealed numerous plasmodia in the blood vessels of the gill filaments. The site of parasite development was the wall of the large-caliber blood vessel of the gill filament, with progressive growth towards the lumen, resulting in the obstruction of blood flow, congestion and perivascular edema. The ultrastructural study revealed that the plasmodial wall was composed of two membranes, had numerous pinocytic canals and was in direct contact with the basement membrane of the vessel. The development of the parasite was asynchronous, with mature spores, immature spores and young developmental stages randomly distributed throughout the plasmodium. The prevalence of the parasite was 4.4%. with male and female fish being infected. (C) 2009 Elsevier B.V. All rights reserved.

Light and scanning electron microscopy of Henneguya arapaima n. sp (Myxozoa: Myxobolidae) and histology of infected sites in pirarucu (Arapaima gigas: Pisces: Arapaimidae) from the Araguaia River, Brazil

In this report, we describe Henneguya arapaima n. sp., a parasite of the gill arch and gall bladder of Arapaima gigas (pirarucu) collected in the Araguaia River, in the municipality of Nova Crixas, Goias State, central Brazil. The plasmodia were white, round or ellipsoidal and measured 200-600 mu m. Parasite development was asynchronous and the mature spores were fusifonn and had smooth wall. The spores measurements were (range, with means +/- S.D. in parentheses): total length-48.4-53.1 mu m (51.6 +/- 3.4 mu m), body length-13.5-15.2 mu m (14.2 +/- 0.8 mu m), body width-5.1-6.1 mu m (5.7 +/- 0.5 mu m), body thickness-4.7-5.3 mu m (4.9 +/- 0.2 mu m) and caudal process length-38.0-41.2 mu m (38.3 +/- 2.9 mu m). The polar capsules were elongated and of unequal size, with lengths of 6.3-6.8 mu m (6.5 +/- 0.2) and 6.2-6.6 mu m (6.3 +/- 0.1) for the longest and shortest axes, respectively. Capsule width was 1.4-1.6 mu m (1.5 +/- 0.1). Histological analysis showed that the plasmodia occurred in the tunica adventitia of the gall bladder and were delimited by a thin capsule of connective tissue. In the gill arch, the plasmodia were also surrounded by connective tissue similar to the endomesium, of striated skeletal muscle cells. Sixty-five juvenile specimens of A. gigas weighing 1.0-25.0 kg were examined, 17 (26.1%) of which were infected. Of these, 14 (82.3%) had cysts in the gall bladder, two (11.7%) had cysts in the gill arch and only one (5.9%) had cysts in both organs. When the fish were grouped by weight, the prevalence of infection in fish weighing up to 10.0 kg (20.7%) was significantly lower than in fish weighing 10.1-25.0 kg (50%) (G = 3.93; d.f. = 1; p < 0.05). (C) 2008 Elsevier B.V. All rights reserved.

Efficient but destructive: a test of the dental wash technique using secondary electron microscopy

The Boyadjian et al dental wash technique provides, in certain contexts, the only chance to analyze and quantify the use of plants by past populations and is therefore an important milestone for the reconstruction of paleodiet. With this paper we present recent investigations and results upon the influence of this method on teeth. A series of six teeth from a three thousand years old Brazilian shellmound (Jabuticabeira II) was examined before and after dental wash. The main focus was documenting the alteration of the surfaces and microstructures. The status of all teeth were documented using macrophotography, optical light microscopy, and atmospheric Secondary Electron Microscopy (aSEM) prior and after applying the dental wash technique. The comparison of pictures taken before and after dental wash showed the different degrees of variation and damage done to the teeth but, also, provided additional information about microstructures, which have not been visible before. Consequently we suggest that dental wash should only be carried out, if absolutely necessary, after dental pathology, dental morphology and microwear studies have been accomplished. (C) 2010 Elsevier Ltd. All rights reserved.

A light and scanning electron microscopy study of bone healing following inferior alveolar nerve lateralization: An experimental study in rabbits

Purpose: The purpose of this study was to evaluate the bone healing kinetics around commercially pure titanium implants following inferior alveolar nerve (IAN) lateralization in a rabbit model. Materials and Methods: Inferior alveolar nerve lateralization was performed in 16 adult female rabbits (Oryctolagus cuniculus). During the nerve lateralization procedure, 1 implant was placed through the mandibular canal, and the IAN was replaced in direct contact with the implant. During the 8-week healing period, various bone labels were administered for fluorescent microscopy analysis. The animals were euthanized by anesthesia overdose, and the mandibular blocks were exposed by sharp dissection. Nondecalcified samples were prepared for optical light and scanning electron microscopy (SEM) evaluation. Results: SEM evaluation showed bone modeling/remodeling between the IAN and implant surface. Fluorochrome area fraction labeling at different times during the healing period showed that bone apposition mainly occurred during the first 2 weeks after implantation. Conclusions: The results obtained showed that bone healing/deposition occurred between the alveolar nerves in contact with a commercially pure titanium implant. No interaction between the nerve and the implant was detected after the 8-week healing period. Appositional bone healing occurred around the nerve bundle structure, restoring the mandibular canal integrity and morphology.

Bone growth around silicon nitride implants - An evaluation by scanning electron microscopy

Silicon nitride has demonstrated to be a potential candidate for clinical applications because it is a non-cytotoxic material and has satisfactory fracture toughness, high wear resistance and low friction coefficient. In this paper, samples of silicon nitride, which were kept into rabbits` tibias for 8 weeks, and the adjacentbone tissue were analysed by scanning electron microscopy in order to verify the bone growth around the implants and the interaction between the implant and the bone. Bone growth occurred mainly in the cortical areas, although it has been observed that the newly bone tends to grow toward the marrow cavity. Differences were observed between the implants installed into distal and proximal regions. In the first region, where the distance between the implant and the cortical bone is greater than in the proximal region, the osteoconduction process was evidenced by the presence of a bridge bone formation toward the implant surface. The results showed that silicon nitride can be used as biomaterial since the newly bone grew around the implants. (c) 2007 Elsevier Inc. All rights reserved.

Transmission electron microscopy characterization of the bake-hardening behavior of transformation-induced plasticity and dual-phase steels

The effect of prestraining (PS) and bake hardening (BH) on the microstructures and mechanical properties has been studied in transformation-induced plasticity (TRIP) and dual-phase (DP) steels after intercritical annealing. The DP steel showed an increase in the yield strength and the appearance of the upper and lower yield points after a single BH treatment as compared with the as-received condition, whereas the mechanical properties of the TRIP steel remained unchanged. This difference appears to be because of the formation of plastic deformation zones with high dislocation density around the “as-quenched” martensite in the DP steel, which allowed carbon to pin these dislocations, which, in turn, increased the yield strength. It was found for both steels that the BH behavior depends on the dislocation rearrangement in ferrite with the formation of cell, microbands, and shear band structures after PS. The strain-induced transformation of retained austenite to martensite in the TRIP steel contributes to the formation of a complex dislocation structure.

Transmission electron microscopy investigation of substitution reactions from carbon nanotube template to silicon carbide nanowires

Substitution reactions between multiwalled carbon nanotubes and silicon monoxide vapour have been investigated using transmission electron microscopy. Different reactions occurred inside the multiwalled nanotubes and on the nanotube external surfaces, resulting in the formation of silicon carbide nanowires with a core–shell structure. The substitution reaction process and end products are strongly affected by nanotube structures and a ball milling treatment of the starting materials.

Silver sulfide as a staining agent for scanning electron microscopy of nylon 6/MXD6 blends

BACKGROUND: In transmission and scanning electron microscopy imaging, the ability to obtain sufficient contrast between the components of a blend when they are both of a similar chemical structure still remains problematic. This paper investigates the domain morphology of a polymer blend containing two polyamides, nylon 6 and the semi-aromatic polyamide poly(m-xylene adipamide) (MXD6), using scanning electron microscopy in backscattered electron imaging mode. The efficiency of three staining agents, ruthenium tetroxide, phosphotungstic acid and silver sulfide, in obtaining optimum phase contrast between the two polymers is discussed.
RESULTS: The use of silver sulfide as a staining agent was found to be a fast and reliable approach which required basic sample preparation and provided excellent compositional contrast between the phases present in the nylon 6/MXD6 blends compared to the other staining agents.
CONCLUSIONS: The technique described in this paper is believed to be a novel and versatile method that has the potential to further improve the ability to study complex polymer blends where one polymer contains an aromatic ring.

A surface characterisation and microstructural study by scanning electron microscopy of the N-methyl-n-alkylpyrrolidinium tetrafluoroborate organic salts

A microstructural characterisation of the family of N-methyl-N-alkylpyrrolidinium tetrafluoroborate organic salts was carried out by observation of powder surface morphologies with the aim of extending the microstructure-property correlation. Inherent difficulties limiting extensive studies of organic solids by SEM, including volatility under vacuum, charging due to electron beam irradiation, and air-sensitivity were overcome with the use of a Field Emission SEM and cryostage attachment. This technique, providing considerable improvements in image quality at low accelerating voltages, enabled direct observation of complex microstructural features in samples exhibiting high temperature plastic crystalline phases (N,N-dimethylpyrrolidinium tetrafluoroborate [P11BF4]; N-methyl-N-ethylpyrrolidinium tetrafluoroborate [P12BF4]; N-methyl-N-propylpyrrolidinium tetrafluoroborate [P13BF4]). Extensive lattice imperfections including grain boundaries, slip planes and dislocation pits were observed within particles of approximately 200 mgrm diameter. The N-methyl-N-butylpyrrolidinium tetrafluoroborate (P14BF4) sample in this series revealed columnar single crystals with high aspect ratios. The origin of plastic flow properties is discussed using single crystal and polycrystalline slip observations and a relationship proposed between defect characteristics and transport properties.

Interfacing cell-based assays in environmental scanning electron microscopy using dielectrophoresis

Development of the dielectrophoretic (DEP) live cell trapping technology and its interfacing with the environmental scanning electron microscopy (ESEM) is described. DEP microelectrode arrays were fabricated on glass substrate using photolithography and lift-off. Chip-based arrays were applied for ESEM analysis of DEP-trapped human leukemic cells. This work provides proof-of-concept interfacing of the DEP cell retention and trapping technology with ESEM to provide a high-resolution analysis of individual nonadherent cells.

Cryo-electron microscopy and single molecule fluorescent microscopy detect CD4 receptor induced HIV size expansion prior to cell entry

Viruses are often thought to have static structure, and they only remodel after the viruses have entered target cells. Here, we detected a size expansion of virus particles prior to viral entry using cryo-electron microscopy (cryo-EM) and single molecule fluorescence imaging. HIV expanded both under cell-free conditions with soluble receptor CD4 (sCD4) targeting the CD4 binding site on the HIV-1 envelope protein (Env) and when HIV binds to receptor on cellular membrane. We have shown that the HIV Env is needed to facilitate receptor induced virus size expansions, showing that the 'lynchpin' for size expansion is highly specific. We demonstrate that the size expansion required maturation of HIV and an internal capsid core with wild type stability, suggesting that different HIV compartments are linked and are involved in remodelling. Our work reveals a previously unknown event in HIV entry, and we propose that this pre-entry priming process enables HIV particles to facilitate the subsequent steps in infection.