Polyoxometalate-Guanosine Monophosphate Hydrogels with Haloperoxidase-like Activity for Antibacterial Performance

Haloperoxidases represent an important class of enzymes that nature adopts as a defense mechanism to combat the colonial buildup of microorganisms on surfaces, commonly known as biofouling. Subsequently, there has been tremendous focus on the development of artificial haloperoxidase mimics that can catalyze the oxidation of X- (halide ion) in the presence of H2O2 to form HOX. The natural intermediate HOX disrupts the bacterial quorum sensing, thus preventing biofilm formation. Herein, we report a simple method for the formation of supramolecular hydrogels through the self-assembly of Keggin-structured polyoxometalates, phosphotungstic acid, and silicotungstic acid with the small biomolecule guanosine monophosphate (GMP) in an aqueous medium. The polyoxometalate-GMP hydrogels that contained highly entangled nanofibers were mechanically robust and showed thixotropic properties. The gelation of the polyoxometalates with GMP not only rendered manifold enhancement in biocompatibility but also the fibril network in the hydrogel provided high water wettability and the polyoxometalates acted as an efficient haloperoxidase mimic to trigger oxidative iodination, as demonstrated by a haloperoxidase assay. The antifouling activity of the phosphotungstic acid-GMP hydrogel was demonstrated against both Gram-positive and Gram-negative bacteria, which showed enhanced antibacterial performance of the hydrogel as compared to the polyoxometalate alone. We envision that the polyoxometalate-GMP hydrogels may facilitate mechanically robust coatings in a simple pathway that can be useful for antifouling applications.

Durability assessment of hydrogel mountings for contrast-enhanced micro-CT

Micro-computed tomography (micro-CT) provides valuable data for studying soft tissue, though it is often affected by sample movement during scans and low contrast in X-ray absorption. This can result in lower image quality and geometric inaccuracies, collectively known as 'artefacts'. To mitigate these issues, samples can be embedded in hydrogels and enriched with heavy metals for contrast enhancement. However, the long-term durability of these enhancements remains largely unexplored. In this study, we examine the effects of two contrast enhancement agents - iodine and phosphotungstic acid (PTA) - and two hydrogels - agarose and Poloxamer 407 - over a 14-day period. We used Drosophila melanogaster as a test model for our investigation. Our findings reveal that PTA and agarose are highly durable, while iodine and poloxamer hydrogel exhibits higher leakage rates. These observations lay the foundation for estimating contrast stabilities in contrast-enhanced micro-CT with hydrogel embedding and serve to inform future research in this field.

Synthesis and comparison of three photocatalysts for degrading tramadol as an analgesic and widely used drug in water samples

Tramadol is an analgesic drug that is mainly excreted in the urine. The entry of Tramadol into water samples causes their biological contamination. Therefore, three catalysts such as bismuth ferrite, cobalt-doped bismuth ferrite, and a magnetized Keggin type of polyoxometalate (α-Fe₂O₃@phosphotungstic acid), were synthesized as photocatalysts to degrade Tramadol in water samples. The morphology and properties of the prepared photocatalysts were evaluated using several techniques. Effects of several factors, including tramadol concentration, pH, hydrogen peroxide concentration, and photocatalyst amount, were studied and optimized by a design experiment procedure based on Box-Behnken design for reducing the number of experiments and cost and investigating the interactions between factors in the photocatalytic degradation process of Tramadol. These factors were optimized for each prepared photocatalyst individually. Under the optimum conditions, the percentages of tramadol degradation and kinetics of the degradation process were evaluated in the presence of each photocatalyst. The tramadol degradation percentages using bismuth ferrite, cobalt-doped bismuth ferrite, and α-Fe₂O₃ @phosphotungstic acid were 81.10% for 120 min, 90.63% for 80 min, and 91.32% for 80 min, respectively. The rate constants of tramadol degradation were 0.0145, 0.0329, and 0.0312 min^-1 for bismuth ferrite, cobalt-doped bismuth ferrite, and α-Fe₂O₃ @phosphotungstic acid, respectively. The results indicated the highest percentage of tramadol degradation and rate of the degradation process were obtained using α-Fe₂O₃ @phosphotungstic acid and cobalt-doped bismuth ferrite, respectively.

Phosphotungstic Acid-treated Picrosirius Red Staining Improves Whole-slide Quantitative Analysis of Collagen in Histological Specimens

We tried to prevent nonspecific nuclear staining (NS-NS) of picrosirius red (PSR) staining by treating the specimens with one of the heteropoly acids phosphotungstic acid (PTA). We analyzed a total of 35 cases of non-cancerous liver tissue for fibrosis and NS-NS under PSR-alone, phosphomolybdic acid (PMA)-pretreated PSR (PMA + PSR), or PTA-pretreated PSR (PTA + PSR) condition. In addition, we analyzed the photosensitivity of PMA or PTA single stain specimens. PTA + PSR significantly suppressed NS-NS compared with PSR. The color of the specimens did not change into blue by 30 times the exposure to whole slide scanner (WSS) light. The PTA + PSR condition showed the highest correlation with the Ishak score (pathological evaluation of liver fibrosis) compared with other conditions. Furthermore, Sirius Red-positive percentage (SRP%) in PSR was increased in the NS-NS observed cases. SRP% in PMA + PSR was significantly affected by WSS light exposure time. Moreover, the deposition of non-polarized PSR-stained substances (NP-PSR+S) clinging to the collagen fibers potentially explains why SRP% seemed bigger under PSR than PTA + PSR. Our protocol enabled us to analyze the whole slide image of PSR staining by high magnification, which would contribute to the accurate analysis of collagen amount in the tissue sections.

Comparing Cs+ binding affinity of Keggin type polyoxometalate and sodium Tetrakis(4-florophenyl)borate in solution and from Cs-doped pure phase vermiculite

We assessed the aptitude of cesium (Cs⁺) binding by Keggin type polyoxometalates (POMs) and compared the results with the Cs⁺ binding by sodium tetrakis(4-fluorophenyl)-borate (Na-TFPB). In this work, we aimed to establish a system to treat radioactive Cs⁺ contaminated soil with POMs economically. We evaluated the effect of initial Cs⁺ concentration (0.1M) and precipitant (POMs and TFPB) concentrations (0.01M) on Cs⁺ precipitation. Our comparison of Cs⁺ precipitation by three different POMs and TFPB was obtained by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). We synthesized POMs molybdovanadophosphoric acid, H₅PMo₁₀V₂O₄₀ (MVPA), and silicotungstic acid, H₄SiW₁₂O₄₀ (STA), and used commercially available phosphotungstic acid, H₃PW₁₂O₄₀ (PTA), and TFPB. Cs-doped pure phase vermiculite was also used to demonstrate the extraction potential of Cs⁺ by TFPB, STA, and PTA. All the POMs and corresponding Cs-bound POMs were characterized by UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray powder diffraction (XRD). In this simulation study, we demonstrated that the Cs⁺ removal by POMs is much more effective than TFPB and could be a promising method for the treatment of radiocesium contaminated soil.

Integrating phosphotungstic acid-assisted prerefining with cellulase treatment for enhancing the reactivity of kraft-based dissolving pulp

Viscosity control and reactivity enhancement are of practical importance for high-quality dissolving pulp manufacturing. In this work, we demonstrate a two-step activating process consisting of a phosphotungstic acid (PTA)-assisted prerefining (PTA/R pretreatment), followed by cellulase treatment for this purpose. The cellulase adsorption can increase from 29.1% to 49.7% as a result of PTA/R pretreatment (8000 r at 90 °C). The viscosity of the resultant pulp decreases from 665 to 430 mL/g, while its Fock reactivity increases from 31.5% to 74.4% under a low-loading cellulase treatment (0.5 mg cellulase /g odp), which mainly due to the fact that the PTA/R pretreatment can increase fiber accessibility and viscosity control, thus facilitating cellulase adsorption and reaction efficiency. Moreover, PTA also shows a high recyclability/ reusability (more than 86%) during the PTA/R pretreatment. Therefore, the new proposed two-step activating process provides a green, and efficient pathway for large-scale manufacturing of high-quality dissolving pulp.

Reduction of N2O by H2 Catalyzed by Keggin-Type Phosphotungstic Acid Supported Single-Atom Catalysts: An Insight from Density Functional Theory Calculations

In the present paper, the mechanisms of N₂O reduction by H₂ were systemically examined over various polyoxometalate-supported single-atom catalysts (SACs) M₁/PTA (M = Fe, Co, Mn, Ru, Rh, Os, Ir, and Pt; PTA = [PW₁₂O₄₀]^3-) by means of density functional theory calculations. Among these M₁/PTA SACs, Os₁/PTA SAC possesses high activity for N₂O reduction by H₂ with a relatively low rate-determining barrier. The favorable catalytic pathway involves the first and second N₂O decomposition over the Os₁/PTA SAC and hydrogenation of the key species after the second N₂O decomposition. Molecular geometry and electronic structure analyses along the favorable reaction pathway indicate that a strong charge-transfer cooperative effect of metal and support effectively improves the catalytic activity of Os₁/PTA SAC. The isolated Os atom not only plays the role of adsorption and activation of the N₂O molecule but also works as an electron transfer medium in the whole reaction process. Meanwhile, the PTA support with very high redox stability has also been proven to be capable of transporting the electron to promote the whole reaction. We expect that our computation results can provide ideas for designing new SACs for N₂O reduction by using H₂ selective catalytic reduction technology.

Damaged starch derived carbon foam-supported heteropolyacid for catalytic conversion of cellulose: Improved catalytic performance and efficient reusability

To develop an efficient heterogeneous catalyst with good stability and reusability for catalytic conversion of cellulose to platform compounds, carbon foam (CF) was used to immobilize phosphotungstic acid (HPW) to prepare CF-supported HPW (HPW/CF) catalyst. Three-dimensional CF was prepared by carbonization of bread (precursor of CF) with mechanical activation (MA)-damaged starch, gluten protein, and yeast as materials. CF30 (30 wt% of gluten protein) exhibited good mechanical strength, relatively high specific surface area, and desired hierarchical porous structure. HPW was successfully anchored onto CF30 by grafting to prepare HPW/CF30 catalyst, which could effectively catalyze the hydrolysis of cellulose to produce glucose, especially for the hydrolysis of MA-pretreated cellulose with small granules and amorphous structure. The affinity between free hydroxyl groups of MA-pretreated cellulose and oxygen-containing groups of CF30 enhanced the catalytic efficiency of HPW/CF30. In addition, HPW/CF30 catalyst exhibited good reusability and was easily separated from reaction system for recycling.

Alternative staining methods for Lowicryl sections

A number of stains and stain combinations have been identified that, when used with the hydrophilic resin Lowicryl K11M, produce marked improvements over aqueous uranyl and lead salts (UA-Pb) in terms of low granularity, specificity, and range of components contrasted. Three test specimens, tobacco mosaic virus (TMV), starfish sperm, and cultured mouse fibroblasts, were used to evaluate stain characteristics. UA-Pb showed a preference for nuclei acids, which were stained specifically by osmium ammine-B at pH 1.5. A number of stain combinations in which UA was followed or preceded by salts containing barium, manganese, tungsten, molybdenum, and vanadium provided excellent staining of protein-containing components, each stain combination being unique in terms of the degree to which specific components were discriminated. These stains were particularly effective for visualizing internal components of the nucleus where a number of fibrillar and particulate structures not seen with UA-Pb were well contrasted.

Determining collagen distribution in articular cartilage using contrast-enhanced micro-computed tomography

OBJECTIVE

Collagen distribution within articular cartilage (AC) is typically evaluated from histological sections, e.g., using collagen staining and light microscopy (LM). Unfortunately, all techniques based on histological sections are time-consuming, destructive, and without extraordinary effort, limited to two dimensions. This study investigates whether phosphotungstic acid (PTA) and phosphomolybdic acid (PMA), two collagen-specific markers and X-ray absorbers, could (1) produce contrast for AC X-ray imaging or (2) be used to detect collagen distribution within AC.

METHOD

We labeled equine AC samples with PTA or PMA and imaged them with micro-computed tomography (micro-CT) at pre-defined time points 0, 18, 36, 54, 72, 90, 180, 270 h during staining. The micro-CT image intensity was compared with collagen distributions obtained with a reference technique, i.e., Fourier-transform infrared imaging (FTIRI). The labeling time and contrast agent producing highest association (Pearson correlation, Bland-Altman analysis) between FTIRI collagen distribution and micro-CT -determined PTA distribution was selected for human AC.

RESULTS

Both, PTA and PMA labeling permitted visualization of AC features using micro-CT in non-calcified cartilage. After labeling the samples for 36 h in PTA, the spatial distribution of X-ray attenuation correlated highly with the collagen distribution determined by FTIRI in both equine (mean ± S.D. of the Pearson correlation coefficients, r = 0.96 ± 0.03, n = 12) and human AC (r = 0.82 ± 0.15, n = 4).

CONCLUSIONS

PTA-induced X-ray attenuation is a potential marker for non-destructive detection of AC collagen distributions in 3D. This approach opens new possibilities in development of non-destructive 3D histopathological techniques for characterization of OA.

Multifactorial Optimization of Contrast-Enhanced Nanofocus Computed Tomography for Quantitative Analysis of Neo-Tissue Formation in Tissue Engineering Constructs

To progress the fields of tissue engineering (TE) and regenerative medicine, development of quantitative methods for non-invasive three dimensional characterization of engineered constructs (i.e. cells/tissue combined with scaffolds) becomes essential. In this study, we have defined the most optimal staining conditions for contrast-enhanced nanofocus computed tomography for three dimensional visualization and quantitative analysis of in vitro engineered neo-tissue (i.e. extracellular matrix containing cells) in perfusion bioreactor-developed Ti6Al4V constructs. A fractional factorial ‘design of experiments’ approach was used to elucidate the influence of the staining time and concentration of two contrast agents (Hexabrix and phosphotungstic acid) and the neo-tissue volume on the image contrast and dataset quality. Additionally, the neo-tissue shrinkage that was induced by phosphotungstic acid staining was quantified to determine the operating window within which this contrast agent can be accurately applied. For Hexabrix the staining concentration was the main parameter influencing image contrast and dataset quality. Using phosphotungstic acid the staining concentration had a significant influence on the image contrast while both staining concentration and neo-tissue volume had an influence on the dataset quality. The use of high concentrations of phosphotungstic acid did however introduce significant shrinkage of the neo-tissue indicating that, despite sub-optimal image contrast, low concentrations of this staining agent should be used to enable quantitative analysis. To conclude, design of experiments allowed us to define the most optimal staining conditions for contrast-enhanced nanofocus computed tomography to be used as a routine screening tool of neo-tissue formation in Ti6Al4V constructs, transforming it into a robust three dimensional quality control methodology.

In vitro detection of prionemia in TSE-infected cervids and hamsters

Blood-borne transmission of infectious prions during the symptomatic and asymptomatic stages of disease occurs for both human and animal transmissible spongiform encephalopathies (TSEs). The geographical distribution of the cervid TSE, chronic wasting disease (CWD), continues to spread across North America and the prospective number of individuals harboring an asymptomatic infection of human variant Creutzfeldt-Jakob Disease (vCJD) in the United Kingdom has been projected to be ~1 in 3000 residents. Thus, it is important to monitor cervid and human blood products to ensure herd health and human safety. Current methods for detecting blood-associated prions rely primarily upon bioassay in laboratory animals. While bioassay provides high sensitivity and specificity, it requires many months, animals, and it is costly. Here we report modification of the real time quaking-induced conversion (RT-QuIC) assay to detect blood-borne prions in whole blood from prion-infected preclinical white-tailed deer, muntjac deer, and Syrian hamsters, attaining sensitivity of >90% while maintaining 100% specificity. Our results indicate that RT-QuIC methodology as modified can provide consistent and reliable detection of blood-borne prions in preclinical and symptomatic stages of two animal TSEs, offering promise for prionemia detection in other species, including humans.

Plant tissues in 3D via X-ray tomography: simple contrasting methods allow high resolution imaging

Computed tomography remains strongly underused in plant sciences despite its high potential in delivering detailed 3D phenotypical information because of the low X-ray absorption of most plant tissues. Existing protocols to study soft tissues display poor performance, especially when compared to those used on animals. More efficient protocols to study plant material are therefore needed. Flowers of Arabidopsis thaliana and Marcgravia caudata were immersed in a selection of contrasting agents used to treat samples for transmission electron microscopy. Grayscale values for floral tissues and background were measured as a function of time. Contrast was quantified via a contrast index. The thick buds of Marcgravia were scanned to determine which contrasting agents best penetrate thick tissues. The highest contrast increase with cytoplasm-rich tissues was obtained with phosphotungstate, whereas osmium tetroxide and bismuth tatrate displayed the highest contrast increase with vacuolated tissues. Phosphotungstate also displayed the best sample penetration. Furthermore, infiltration with phosphotungstate allowed imaging of all plants parts at a high resolution of 3 µm, which approaches the maximum resolution of our equipment: 1.5 µm. The high affinity of phosphotungstate for vasculature, cytoplasm-rich tissue, and pollen causes these tissues to absorb more X-rays than the surrounding tissues, which, in turn, makes these tissues appear brighter on the scan data. Tissues with different brightness can then be virtually dissected from each other by selecting the bracket of grayscale to be visualized. Promising directions for the future include in silico phenotyping and developmental studies of plant inner parts (e.g., ovules, vasculature, pollen, and cell nuclei) via virtual dissection as well as correlations of quantitative phenotypes with omics datasets. Therefore, this work represents a crucial improvement of previous methods, allowing new directions of research to be undertaken in areas ranging from morphology to systems biology.

UV-H2O2 degradation of methyl orange catalysed by H3PW12O40/activated clay

A catalyst consisting of phosphotungstic acid (H3PW12O40) combined with activated clay was prepared by the impregnation method, and an experiment was carried out to evaluate the catalytic activity of the H3PW12O40/activated clay for the degradation of methyl orange (MO) in the UV-H2O2 process. The degradation ratio of MO can be affected by H2O2 concentration, reaction time, catalyst dosage, pH and temperature. The reaction temperature should be controlled at less than 70 degrees C, and the catalyst has a wide applicable pH range in the UV-H2O2 process. Hydroxyl radicals were generated in the UV-H2O2 system under the action of H3PW12O40/activated clay, and MO was degraded by hydroxyl radicals. Compared with traditional catalysts used in UV-H2O2 systems, H3PW12O40/activated clay has certain advantages for its practical application.

Sperm ultrastructure of Mytella (Bivalvia) populations from distinct habitats along the northern coast of São Paulo State, Brazil

Ultrastructural analyses of bivalve spermatozoa are relevant in studies that aim to identify taxonomic traits for the purposes of discriminating species and conducting phylogenetic studies. In the present work, spermatozoa of mussel specimens of the genus Mytella, collected from two populations living in distinct habitats, were examined by electron microscopy. The objective was to identify sperm ultrastructural taxonomic traits that could be used to differentiate Mytella species. The specimens were from populations that live in intertidal zones on the southeast coast of Brazil, either buried in muddy-sand sediment or anchored to rocky substrates. The acrosomal vesicle was conical and long, the axial rod extended from the nucleus to the acrosome, the nucleus was an oblate spheroid with a condensed chromatin, the intermediate portion contained mitochondria encircling a pair of centrioles, and there was a single flagellum. The sperm was of a primitive type. The spermatozoon ultrastructure did not distinguish the specimens buried in muddy-sand sediment from those anchored to rocky substrates. The data suggest that the specimens analyzed, despite living in distinct habitats, belong to the same species, which conchological analyses identified as M. charruana. The presence of an axial rod in their sperm cells supports the inclusion of M. charruana in the subfamily Mytilinae.

Examination of electron stains as a substitute for uranyl acetate for the ultrathin sections of bacterial cells

Electron staining reagents were examined to find a possible substitute for uranyl acetate (UA) in electron microscopy of bacterial ultrathin sections. Four kinds of stains, platinum blue (Pt-blue), oolong tea extract (OTE), potassium permanganate (KMnO(4)) and phosphotungstic acid (PTA), were examined in comparison with UA either with or without post-staining with lead citrate (Pb). Electron microscopy was performed on sections from Spurr-embedded cells of a Gram-positive bacterium, Bacillus cereus NBRC 13597, and a Gram-negative bacterium, Escherichia coli NBRC 3301. Both Pt-blue and OTE showed staining similar to each other and to that of double staining with UA and Pb in B. cereus, while in E. coli the cytoplasmic membrane appeared less dense when compared with UA and Pb. KMnO(4) stained excessively to some extent, but showed images of the best contrast in the cytoplasmic membrane comparable with UA and Pb among the four reagents. PTA could stain the peptidoglycan layer but gave images of low quality for both bacteria. This study demonstrated that none of the reagents examined showed staining results of the same quality or better than the conventional method with UA and Pb. However, stains of Pt-blue, OTE and KMnO(4) could possibly be an alternative candidate for the UA according to the structure in question.

MicroCT for comparative morphology: simple staining methods allow high-contrast 3D imaging of diverse non-mineralized animal tissues

BACKGROUND

Comparative, functional, and developmental studies of animal morphology require accurate visualization of three-dimensional structures, but few widely applicable methods exist for non-destructive whole-volume imaging of animal tissues. Quantitative studies in particular require accurately aligned and calibrated volume images of animal structures. X-ray microtomography (microCT) has the potential to produce quantitative 3D images of small biological samples, but its widespread use for non-mineralized tissues has been limited by the low x-ray contrast of soft tissues. Although osmium staining and a few other techniques have been used for contrast enhancement, generally useful methods for microCT imaging for comparative morphology are still lacking.

RESULTS

Several very simple and versatile staining methods are presented for microCT imaging of animal soft tissues, along with advice on tissue fixation and sample preparation. The stains, based on inorganic iodine and phosphotungstic acid, are easier to handle and much less toxic than osmium, and they produce high-contrast x-ray images of a wide variety of soft tissues. The breadth of possible applications is illustrated with a few microCT images of model and non-model animals, including volume and section images of vertebrates, embryos, insects, and other invertebrates. Each image dataset contains x-ray absorbance values for every point in the imaged volume, and objects as small as individual muscle fibers and single blood cells can be resolved in their original locations and orientations within the sample.

CONCLUSION

With very simple contrast staining, microCT imaging can produce quantitative, high-resolution, high-contrast volume images of animal soft tissues, without destroying the specimens and with possibilities of combining with other preparation and imaging methods. Such images are expected to be useful in comparative, developmental, functional, and quantitative studies of morphology.

[A simple separative method for measuring serum amyloid A in high-density-lipoprotein and low-density-lipoprotein fractions using the phosphotungstic acid-Mg2+ precipitation procedure]

We developed a simple separative method for measuring serum amyloid A (SAA) in both high-density-lipoprotein (HDL) and low-density-lipoprotein (LDL) fractions. It was devised using the SAA agglutination method and phosphotungstic acid-Mg2+ precipitation procedure for evaluating HDL-cholesterol (HDL-C). The new method is also able to detect amyloid A (AA) in each fraction with precision. The results of both the present method and the method using SAA agglutination and the dextran sulfate-Mg2+ precipitation procedure showed a strong correlation when used to measure the level of SAA in the LDL fraction of patients (r = 0.997; p < 0.0001). Reference intervals in normal healthy subjects (n=75) ranged from 0.5 to 4.7 microg/ml in the HDL fraction and from 0.1 to 1.9 microg/ml in the LDL fraction. SAA in the LDL fraction of subjects with hyperlipidemia was significantly higher than in normal subjects and subjects with normal lipidemia. SAA in the HDL fraction and total sera of subjects with hyperlipidemia was significantly higher than in normal subjects; however, it was not higher than in patients with normal lipidemia. The present methods for detecting SAA, especially in the LDL fraction, might benefit from analyzing patho-physiological events in various lipid disorders.

Malignant stromal tumor, so called "gastrointestinal stromal tumor", with rhabdomyomatous differentiation occurring in the gallbladder

Gastrointestinal stromal tumors (GISTs) constitute the largest category of primary nonepithelial neoplasms of the gastrointestinal tract. It is extremely rare that this tumor occurs in the bile tract, and only a few cases have been reported. Immunohistochemically, the tumor cells revealed a phenotype similar to Cajal cells, occasionally with differentiation to smooth muscle cells or neural cells. We present a case of malignant stromal tumor similar to GISTs with rhabdomyomatous differentiation of the gallbladder in a 68-year-old woman. The resected tumor was predominantly composed of spindle cells with rhabdomyomatous differentiation. Immunohistochemical study revealed diffuse staining of tumor cells using vimentin despite negative staining for desmin or S-100. This indicated a mesenchymal origin of the cells without smooth muscle or neuronal differentiation. Myoglobin-positive cells, in which phosphotungstic acid hematoxylin staining revealed cross striations of the cytoplasm, suggested rhabdomyomatous differentiation. Diffuse positivity for KIT in the cells suggested that the pathogenesis of this tumor may resemble that of GIST. The tumor may have derived from a mesenchymal stem cell that had undergone partial rhabdomyomatous differentiation.

Evaluation of Western blotting methods using samples with or without sodium phosphotungstic acid precipitation for diagnosis of scrapie and chronic wasting disease

The purpose of this study was to enhance the sensitivity of the Western blot (WB) test for use as an alternative and confirmatory method for the diagnosis of scrapie and chronic wasting disease (CWD) in Canada by comparing 2 sample preparation procedures: an abnormal prion protein (PrPSc) concentration procedure using sodium phosphotungstic acid (PTA) precipitation and a procedure using crude sample without precipitation. A total of 100 cerebrum samples (52 sheep and 48 elk), including 66 negative (31 sheep, 35 elk) and 34 positive (21 scrapie and 13 CWD positive) samples diagnosed by using immunohistochemistry (IHC) on retropharyngeal lymph node (RPLN) and medulla oblongata at obex, were tested by using WB with the 2 sample preparation procedures. The WB using non-PTA enriched sample (crude extract) detected, on average, only 71.7% (9 of 15, 60.0% for scrapie, 5 of 6, 83.3% for CWD) of the samples that tested positive by using WB with PTA enriched samples. No case was positive by WB using crude extract but negative by WB using PTA enriched sample. No false positive was found. Serial dilution of PTA precipitated samples demonstrated that the technique increases the detection limit approximately 100 fold. Additionally, the comparison of the WB and IHC on cerebrum from all the positive cases demonstrated that WB following PTA precipitation and IHC had 100% agreement by detecting 6 positive for CWD on cerebrum; while IHC detected scrapie in only 14 out of 15 positive cerebrum samples by using WB following PTA precipitation. Phosphotungstic acid precipitation is therefore a useful adjunct to WB analysis of scrapie and CWD and tissues.

Alterations of N-ethylmaleimide-sensitive atpase following transient cerebral ischemia

Neuronal repair following injury requires recruitment of large amounts of membranous proteins into synaptic and other cell membranes, which is carried out by the fusion of transport vesicles to their target membranes. A critical molecule responsible for assemblage of membranous proteins is N-ethylmaleimide-sensitive factor (NSF) which is an ATPase. To study whether NSF is involved in ischemic neurological deficits and delayed neuronal death, we investigated alterations of NSF after transient cerebral ischemia by means of biochemical methods, as well as confocal and electron microscopy. We found that transient cerebral ischemia induced depletion of free NSF and concomitantly relocalization of NSF into the Triton X-100-insoluble fraction including postsynaptic densities in CA1 neurons during the postischemic period. The NSF alterations are accompanied by accumulation of large quantities of intracellular vesicles in CA1 neurons that are undergoing delayed neuronal death after transient cerebral ischemia. Therefore, permanent depletion of free NSF and relocalization of NSF into the Triton X-100-insoluble fraction may disable the vesicle fusion machinery necessary for repair of synaptic injury, and ultimately leads to synaptic dysfunction and delayed neuronal death in CA1 neurons after transient cerebral ischemia.

Adaptation of the phosphotungstate method to determine reduced and oxidized vitamin C in blood plasma

The phosphotungstate reagent (PTR) was used for quantitative spectrophotometric determination of physiological forms of vitamin C in blood plasma. An immediate action of PTR on the first half of the tested samples allowed to determine reduced vitamin C concentrations (I) at 700 nm. 10 mM dithiothreitol added to the second half of the samples reduced oxidized vitamin C in it--hence the total amount of this vitamin was reduced with a concentration (II) determined as above (remains of dithiothreitol were removed with N-ethylmaleimide). The difference of results (II) and (I) gave the concentration of oxidized vitamin C. The method is characterised by fault-less analytical parameters: correlation coefficients of analytical curves > 0.99, recovery factor 100.5%, variation coefficients intra- and inter-serial < 3% and < 5%, respectively, detection limit 0.05 microM. The simplicity of the method enables an easy control of the ratio of oxidized and reduced vitamin C concentrations in blood plasma--the biomarker of the level of oxidative damage to cells.

Malignant astrocytoma with binucleated granular cells in a Sprague-Dawley rat

A 2-year-old Sprague-Dawley rat with hindlimb paralysis was diagnosed with a cerebral malignant astrocytoma. The distinctive feature of this astrocytoma was the presence of scattered binucleated cells that contained hypereosinophilic, 1-2 micro m in diameter, cytoplasmic granules. The neoplastic astrocytes stained positively for vimentin (VIM), lysozyme, and phosphotungstic acid hematoxylin (PTAH). Within the binucleated cells, granules stained with PTAH and periodic acid-Schiff (PAS) before and after diastase digestion. Ultrastructurally, neoplastic astrocytes were characterized by cytoplasmic aggregates of electron-dense intermediate filaments consistent with VIM and desmin. The cytoplasm of binucleated cells contained numerous phagolysosomes enlarged by myelin figures and glycoprotein or glycolipid. Intermediate filaments were not present. This is the first description, in the rat, of a neoplasm with features resembling the human granular cell astrocytoma. Our findings suggest that an astrocytic origin should be considered for the binucleated cells in this neoplasm.

Electron densitometry of stained virus particles

Methods are described for determining the relative mass of particles in electron microscope specimens through the measurement of photographic densities in recorded images. These methods were applied to a quantitative study of the amounts of electron stains that could be associated with the particles of tomato bushy stunt virus (BSV) and tobacco mosaic virus (TMV). In the pH range above 2 where the viruses are stable, the amount of stain absorbed is too small to produce adequate contrast in the electron microscope. Maximum stain absorption was achieved at pH about 1 where with several reagents and combinations of reagents the mass of BSV could be increased to about four times that of the unstained particles. Optimum results were obtained with phosphotungstic acid alone or in combination with Pt, Th, or La ions. Since the pH conditions for high stain absorption are normally destructive, morphology is satisfactorily preserved only when the phosphotungstic acid is applied in concentrations of 10 per cent or greater or when the use of destructive reagents is preceded by a preliminary fixation under mild conditions. Maximum staining of TMV increased the mass of the particles to about two times that of the unstained. Estimates of the mass of heavily stained BSV particles indicate that their density is 3.3 gm./cm.³ The high internal hydration of BSV probably accounts for the greater stain absorption and penetration compared to those of TMV which has very low or zero internal hydration. Anomalous images resulting from the use of electron stains are shown and discussed.

Adaptation of the phosphotungstate method for the determination of vitamin C contents in animal and human tissues

The usefulness of phosphotungstate reagent for vitamin C determination in tissue homogenates has been confirmed. An optimal homogenization medium was selected: 1.8 M solution of HPO3 in 1.3 M CH3COOH. With this medium the analytical curve (at 700 nm) demonstrated the right linearity, correlation and recovery coefficients were appropriately high (0.999 and 99.8%) and the values of intraserial and interserial variation coefficient were low (< 5% and < 10%, respectively). It makes this method sensitive, easily repeatable, and useful for vitamin C determination in animal and human tissues, including neoplastic ones.