Dehydration Procedure Research Articles

Dehydration of scandium chloride hydrate: synthesis and molecular structures of ScCl 3(η 2-DME)(MeCN), ScCl 3(diglyme) and [Sc 2(μ-OH) 2(H 2O) 10]Cl 4·2H 2O

Various dehydration procedures have been evaluated for ScCl 3·6H 2O. The ScCl 3(DME)(MeCN) 1 and ScCl 3(diglyme) 2 [diglyme=MeO(CH 2CH 2O) 2Me] adducts have been synthesized by a ligand-exchange reaction from ScCl 3(THF) 3 in acetonitrile. The diglyme adduct could also be obtained by dehydration of ScCl 3·6H 2O by trimethylchlorosilane in diethylether in the presence of the ligand. The complexes were characterized by FT–IR, 1H NMR and by X-ray diffraction. They both correspond to monomeric species based on distorted hexacoordinated scandium. Hydrolysis of 2 gave [Sc 2(μ-OH) 2(H 2O) 10]Cl 4·2H 2O, 3. The Sc–O coordination bonds of 1 and of 2 [2.207(1) Å for the DME adduct, 2.165(8)–2.257(9) Å for 2] have lengths comparable to the Sc–O(H 2O) bonds of 3 [2.172(4)–2.217(5) Å], but were longer than the Sc–OH ones [2.064(5) Å]. The dimeric cations, in which the metals are heptacoordinated, are associated by hydrogen bonding (∼ 2.737(5) Å) between coordinated and crystallization-type water molecules. As a result, chains are developed along the a axis.

Changes in Starch Properties of Corn Tortillas during Storage

Starch properties of corn tortillas were characterized during storage. Tortillas were chopped into pieces, macerated with ethanol, centrifuged, extracted again with ethanol, centrifuged, dried, and ground into flour to dehydrate and stabilize starch. Water absorption and water solubility at 25°C, starch pasting properties, and amount and molecular weight of starch extracted at 95°C in water were quantified. Increased levels of soluble amylopectin and increased cold paste viscosity distinguished fresh (0, 0.5, and 1 h) from aged (120 h) tortillas. Water solubility at 25°C decreased continuously during storage; whereas, water absorption increased 0.5 h after baking and then decreased during storage. Rapid changes in starch properties were stabilized using the dehydration procedure and clearly distinguished by pasting viscosities and other methods. Measured starch properties were consistent with very rapid associations (retrogradation) of amylose and rapid associations of amylose and amylopectin yielding insoluble structures in corn tortillas. Retention of some starch crystal nuclei after baking facilitated starch associations that yielded rapid structural changes in corn tortillas.

NMR Studies in Demyelinating and Non-Demyelinating Experimental Allergic Encephalomyelitis

The spinal cords of rats, involved as part of two distinct and reproducible experimental allergic encephalomyelitis animal models, presenting inflammatory white matter lesions with and without demyelination, were studied in vitro by NMR, before and after a dehydration procedure, in order to characterize demyelination. All the parameters of the T₁ and T₂ relaxation times were determined, as well as the initial proportion of the very quickly decaying component of the free induction decay, and the magnetization transfer ratio. The relaxation decays were fitted with the discrete and Contin methods. Magnetization transfer ratio measurements permitted first to evaluate the magnetization transfer at the apex, and secondly to decompose the post-irradiation curves into two components: a gaussian and a lorentzian line, with their relative proportions and widths. The results presented in this study clearly demonstrate that it is not possible to evidence demyelination in fresh spinal cord preparations by NMR. Hovewer, the dehydration procedure, which was introduced with the aim of reducing the amount of free water in our samples, seems sufficient to enable the detection of demyelination from the T₂ relaxation spectra and magnetization transfer data. As a conclusion, we think that the NMR properties of water protons allow to achieve tissue characterization on condition that the parameters concerning free water and its exchanges are eliminated.

Catalytic performance of vanadyl pyrophosphate in the partial oxidation of toluene to benzaldehyde

Vanadyl pyrophosphate catalysts were generated by dehydrating VOHPO4·(1/2)H2O at different temperatures and duration of the dehydration procedure. The as-synthesised materials were characterised by X-ray diffractometry, FTIR spectroscopy and temperature-programmed reduction. The prolongation of the formation period at higher temperatures led to improved crystallinity and lower BET surface areas of the vanadyl pyrophosphate specimens and, additionally, a significantly impeded reducibility of the vanadyl sites was observed. The catalytic performance of the samples was tested in the partial oxidation of toluene to benzaldehyde. The obtained results revealed an increasing benzaldehyde selectivity with improved catalyst crystallinity. In situ FTIR and ESR spectroscopy were used to throw more light on the interaction of the toluene–air feed with the surface of the catalyst.

Novel Gliosarcoma Cell Line Expressing Green Fluorescent Protein: A Model for Quantitative Assessment of Angiogenesis

Angiogenesis is essential for tumor proliferation and metastasis. The extent of angiogenesis is measured by microvessel density (MVD) which has been identified as an independent prognostic factor for relapse-free survival in cancer patients. Existing methods of MVD assessment measure the microvessel count in the most active area of neovascularization (“hot spots”) using antibodies against vascular endothelial antigens. This may produce unreliable results because of tissue volume loss and misshapening during the fixation and dehydration procedures. We report here a genetically engineered 9L cell line constitutively expressing green fluorescent protein that can be visualized using fluorescence microscopy without additional histological staining. The model developed in this study allows for the performance of simple and easy MVD counting, assuming that nonfluorescent “black spots” visible by fluorescence microscopy within the borders of the tumor tissue represent blood vessels. This assumption was confirmed by a comparative study utilizing conventional histological methods, anti-CD31 immunohistology, and Hoechst 33258 dye exclusion. This model is also useful for delineation of the true borders between tumor and normal brain tissue, including microscopic tumor extensions, without multiple histological staining. The suggested model allows quantification of tumor angiogenesis in tissue specimens, thus providing independent prognostic information about tumor growth and regression. It is expected to be most valuable in evaluating the efficacy of anti-angiogenic therapy.

Morphology of the unfixed cochlea

Our knowledge of cochlear geometry is based largely upon anatomical observations derived from fixed, dehydrated, embedded and/or sputter-coated material. We have now developed a novel preparation, the hemicochlea, where for the first time living cochlear structures can be observed in situ and from a radial perspective. The experiments were performed on the Mongolian gerbil. Ion substitution experiments suggest that no significant swelling or shrinkage occurs when the preparation is bathed in normal culture medium, so long as calcium concentration is kept at endolymph-like (20 μM) levels. The tectorial membrane-reticular lamina relationship appears to remain well preserved. Hensen's stripe maintains a close relationship with the inner hair cell stereociliary bundle, unless the mechanical coupling becomes disturbed. In addition, standard fixation and/or dehydration procedures are used to quantify changes due to shrinkage artifacts. Various morphometric gradients are examined in unfixed specimens from apical, middle, and basal turns.

Dehydration, Diffusion and Entrapment of Zinc in Bentonite

AbstractInteractions with bentonite are important in the chemical speciation and fate of heavy metals in soils and other ecosystems. The interactions of Zn with bentonite were studied using X-ray diffraction (XRD), dehydration, kinetic and sequential extraction procedures. The species and activity of Zn retained by bentonite were affected markedly by pH. The Zn(OH)+ was retained by bentonite prepared at pH ≥ 6.9. The extent of dehydration of Zn(OH)+-bentonite was higher than that for Zn-bentonite. At a relative humidity of 55.5%, the basal spacing of the Zn(OH)+-bentonite was from 1.21 to 1.26 nm with 1 water sheet and that of the Zn-bentonite was 1.51 nm with 2 water sheets. The greater affinity of Zn(OH)+ for bentonite than Zn was associated with a lower degree of hydration. When an aqueous suspension of Ca-bentonite was incubated with soluble Zn, the concentration of Zn retained by the Ca-bentonite was linearly related to the square root of time. The rate of the interaction was controlled probably by the interlayer diffusion and subsequently by the diffusion into the ditrigonal cavities in bentonite. The Zn retained by bentonite was dehydrated in situ so as to increase the bonding of Zn with surfaces of bentonite. With hydrothermal treatment the retained Zn could diffuse easily into the cavities and transform increasingly to the residual forms that are associated with the entrapped form.

Morphometric analysis of ageing mushrooms (Agaricus bisporus) during postharvest development

Abstract During postharvest development of the basidiocarp of Agaricus bisporus cv.U1, growth takes place in the pileus, stipe and gills. The average cell area in periclinal sections of pileus tissue increases about 5–6 fold. Although the morphology changes, the pileus of the mushroom as a whole does not enlarge, implying that only a minority, estimated to be less than 20% of the cells, are destined to grow by vacuolar expansion at the cost of other cells. This is in contrast with growth of the gill tissue, as measured in the supporting tissue (the trama), where cells are enlarging in a radial direction by increasing both vacuole volume and cytoplasm content. However, the absence of an increase in average cell size in the longitudinal direction does not match the growth and growth direction of the gill tissue as a whole. This can only be explained by assuming that each cell in the gill tissue has to divide in the longitudinal direction. Since the stipe architecture shows large variation, observed changes in cell size at one specific point cannot be used to explain macroscopic changes of the stipe as a whole. A new method for correcting shrinkage due to fixation and dehydration procedures has also been developed. This method might be useful for a range of organisms in which measurements of absolute or relative cell sizes and intercellular space are required.

Use of peroxidase substrate Vector VIP® for multiple staining in light microscopy

The study of the distribution of a fiber input to a particular brain area and the visualization of the anatomical relationships of that input with both projection- and interneurons, requires a triple-staining that allows the unequivocal distinction of each of the three components in one and the same histological section. In this regard, we investigated the properties of a recently introduced peroxidase chromogen, VIP® (V-VIP; Vector Labs) in combination with two traditional substrates, standard diaminobenzidine (DAB, brown precipitate) and nickel-enhanced DAB (DAB-Ni, black). In rats, the anterograde tracer biotinylated dextran amine (BDA) and the retrograde tracer fluorogold (FG) were injected in the perirhinal cortex and hippocampus, respectively. Transported BDA was detected with an avidin-biotin-peroxidase complex, whereas the transported FG was detected via a PAP method. Tracing with BDA and FG was combined with parvalbumin- or calbindin-immunocytochemistry. We compared various combinations and staining sequences. The best results were obtained with a staining sequence comprising first the BDA stain with DAB-Ni as chromogen, second the FG protocol with the chromogen DAB and finally, parvalbumin- or calbinding-immunocytochemistry using the chromogen V-VIP. The order with which the chromogens were applied appeared to be critical. Partial or even total loss of V-VIP reaction product has been observed after standard dehydration in ethanol. As an alternative, a quick dehydration procedure in toluene yields much better staining. Colour separation is excellent and the sensitivity is high. This procedure may also be used for detection of any other combination of three different labels, taking the usual care to avoid cross-reactivity between antibodies.

The use of different fixatives and hydrophilic embedding media (Historesin™ and Unicryl™) for the study of embryonic tissues

The effects of different fixatives, dehydration procedures, and embedding media on the structural and ultrastructural preservation of young chick embryos (Hamburger and Hamilton stages 18-24) have been studied by means of light and electron microscopy techniques. Under the light microscope, the results obtained with the use of Bouin, glutaraldehyde, or glutaraldehyde-paraformaldehyde mixtures, followed by partial dehydration of the samples and the embedding with two different polar resins (Historesin and Unicryl), were compared with the results obtained using conventional paraffin-embedding methods. Cell and tissue shrinkage was determined by comparing blood cells from those embryos embedded in either of resins with those embedded in paraffin. Samples were also compared with blood smears, either methanol-fixed or unfixed, obtained from embryos at the same Hamburger and Hamilton stages. The results obtained when Unicryl and Araldite were used for electron microscopy have also been compared. When ultrastructural images from glutaraldehyde-tannic acid/osmium tetroxide fixed, Unicryl embedded samples were compared with those from araldite embedded samples, the same good results were observed with either of the resins. Araldite embedding requires a complete dehydration of the samples, while Unicryl allows the embedding of partially dehydrated embryos with optimal ultrastructural results. We suggest that these polar resins can be considered as complementary tools for embedding delicate embryonic tissues, allowing partial dehydration of the specimens with an excellent cell and tissue preservation.

Collagen fibril surface: TMAFM, FEG-SEM and freeze-etching observations.

Native, unfixed collagen fibrils from rat tail tendon were dehydrated following different procedures and observed under a FEG-SEM and an AFM operated in Tapping Mode (TMAFM). Freeze-etched, untreated fibrils from the same tissue were also observed for comparison. The most notable features of the fibril surface, i.e., the gap/overlap alternation and three prominent intraperiod ridges, were simultaneously visible only in freeze-etched specimens, while under the SEM and the TMAFM their appearance was dependent on both the dehydration procedure and the visualization technique. The different susceptibility of the collagen fibril surface structures to various treatments clearly implies the existence of domains of different composition. Moreover, identical specimens were imaged differently by SEM and TMAFM, highlighting instrument-specific advantages and limitations. The onset of dehydration-dependent, procedure-specific artifacts should be considered in high-resolution studies of connective tissues. As for any biological specimen, the final aspect of collagen fibrils is determined no less by the preliminary treatments than by the visualization approach.

Tannic acid supplemented fixation improves ultrastructural evaluation of respiratory epithelium in children with recurrent respiratory tract infections.

Samples of the respiratory mucosa of children with recurrent respiratory infections suspected of having primary ciliary dyskinesia are routinely fixed with glutaraldehyde before ultrastructural examination. This standard technique, however, may not be optimal for visualizing ciliary components or for preserving several cellular and extracellular structures during dehydration and embedding procedures. In this study, brushes of nasal (28 samples) and/or tracheal (9 samples) mucosa from 32 children with recurrent respiratory tract infections were examined. Twenty-nine samples were fixed with glutaraldehyde supplemented with tannic acid to determine if the ultrastructural analysis of respiratory epithelium and bronchial secretions could be improved. Eight samples were conventionally fixed with glutaraldehyde alone. Lesions of the cellular membrane and damaged cells were easily visualized using tannic acid supplemented fixation. Internal ciliary structures including individual microtubules and dynein arms were also more clearly observed. In addition, the internal structure of microvilli of the respiratory epithelium could be studied and the presence of phospholipid-rich surfactant-like material within nasal and tracheal secretions were visualized after tannic acid supplemented fixation. We suggest that addition of tannic acid during fixation is useful for accurate ultrastructural evaluation of respiratory mucosa in both clinical and experimental situations.

Surface morphology of the endolymphatic duct in the rat. A scanning electron microscopy study.

Following intracardiac vascular perfusion fixation of 8 rats with glutaraldehyde in a buffered and oxygenated blood substitute, the vestibular aqueduct and endolymphatic duct were opened by microsurgery of the resulting 16 temporal bones. Optimum preservation of the epithelium for scanning electron microscopy was attained by coating of the specimens with osmium tetroxide and thiocarbohydrazide followed by a continuous dehydration procedure. This technique permitted, for the first time, an investigation of the surface morphology of the epithelial cells in the endolymphatic duct. Three types of cells were identified with the scanning electron microscope. A polygonal and oblong epithelial cell was observed in the largest number throughout the duct, and in the juxtasaccular half of the duct, two additional types of epithelial cells were observed. The scanning electron microscopic observations are compared and discussed with reference to previous transmission electron microscopic studies of the endolymphatic duct.

Displacement of Acid Phosphatase and Alkaline Phosphatase Proteins in the Rat Kidney during a Dehydration Procedure. An Advantage of Ultrathin Frozen Sections for Detecting Precise Localization of an Enzyme Activity.

Displacement of Acid Phosphatase and Alkaline Phosphatase Proteins in the Rat Kidney during a Dehydration Procedure. An Advantage of Ultrathin Frozen Sections for Detecting Precise Localization of an Enzyme Activity.

Fine structure of the endolymphatic duct in the rat. A scanning and transmission electron microscopy study.

To investigate the surface morphology of the endolymphatic duct epithelium, 8 rats were vascularly perfused with glutaraldehyde in a buffered and oxygenated blood substitute. Optimal preservation of the epithelium for scanning electron microscopy was attained by coating of the specimens with OsO4 and thiocarbohydrazide followed by a continuous dehydration procedure. Three types of cells were identified with the scanning electron microscope: A polygonal and oblong epithelial cell was observed in the largest number throughout the duct, whereas in the juxta-saccular half of the duct two additional types of epithelial cells were observed. The scanning electron microscopical observations are compared and discussed with reference to transmission electron microscopical observations of the endolymphatic duct.

Non-Destructive Collection of Apoplast Fluid From Developing Tomato Fruit Using a Pressure Dehydration Procedure

Pressure dehydration techniques were evaluated for the collection of samples of apoplast fluid from the outer pericarp tissues of developing tomato fruit. Sap was expelled under pressure through a cannula inserted into the selected tissue of a fruit sealed in a Scholander pressure bomb. Osmolality and concentrations of K+ and hexoses were significantly lower and pH higher in sap exudates than in bulk fruit tissues. After infusion of fruit with trisodium 3-hydroxy-5,8,10-pyrenetrisulfonate as an apoplastic marker, the dye was confined to the same fruit compartment as that which yielded sap under pressure. During extended periods of sap exudation at 24�C under 1.4 MPa or more, the initial 100 μL of exuded sap was obtained without contamination from protoplasmic contents followed by a proportionate increase in sap osmolality with the aggregate volume. However, when the exuded sap was collected at 4�C under the applied pressure of 0.6-1.0 MPa, the composition of the sap remained constant with time and was independent of the applied pressure. This permits the collection of a relatively large volume of exuded fluid, up to about 500 μL sap per 70 g fruit, at an initial flow rate of 100-150 μL h-1. We conclude that the pressure dehydration technique under the described conditions allows the collection of uncontaminated apoplastic fluid from the pericarp of intact developing tomato fruit.

Ultrastructure of Human Skin by a Rapid Freezing Technique: Structural Preservation and Antigenicity

To investigate the natural fine structure of skin, human skin biopsies were studied by electron microscopy and immunoelectron microscopy using rapid freezing and freeze-substitution techniques. Well-preserved structures were observed within a depth of 20 microns from the slammed surface of the samples. Epidermal cells were always closely located with very narrow intercellular spaces. Keratin filaments were distributed densely and homogeneously without forming bundles in the cytoplasm of epidermal keratinocytes. Langerhans cell granules were composed of a flat vesicular portion and an oval rod portion. The most striking finding was in the dermal-epidermal junction, where the lamina densa was present but no lamina lucida was observed. Further, by immunoelectron microscopy with anti-keratin monoclonal antibody, the 20-microns-deep part of the samples revealed the most significant staining. These findings indicate that the ultrastructure of routinely processed skin samples may be modified during the procedure for conventional chemical fixation and dehydration and that the ultrastructurally most preserved specimens, reflecting the conditions close to natural in vivo structures of the skin, can be obtained by the techniques described in this paper.

High-accuracy thermal analysis of the solid-solid phase transition of lithium sulfate powders

Powder samples of Li 2SO 4 from three different manufactures were analysed using an accurate high-resolution heat flow calorimeter. It is shown that some of the results presented are endowed with more than ten times smaller uncertainty limits than are usually encountered in the technical literature covering the state of the art of thermal analysis. Details of the measuring system are given, and reasons for the higher accuracy are discussed. The average enthalpy change associated with the transformation between the two high temperature forms of solid lithium sulfate, resulted in δ H = 26.1 ± 1.7 kJ mol −1. The relatively large uncertainty (twice as large as expected from the calorimeter's performance) is due to unexplained differences between the three powder samples investigated. Different transformation temperatures were determined for each one of the samples. The origin of the differences, as well as the shape of the measured heat-flow curves, can be explained semi-quantitatively by means of the Gibbs-Thomson effect, in terms of the size distribution of the crystallites that compose the sample, which should depend on its initial granulometry and the dehydration procedure used. The onset temperatures for the monoclinic to cubic transformation, for sample 1 (Aldrich), sample 2 (Merck), and sample 3 (Alfa), are 577.82 ± 0.08, 577.98 ± 0.05 and 578.30 ± 0.03°C, respectively. They are believed to represent the transformation temperature of the smallest crystallites present in the sample. Extrapolated temperatures, representative of the transformation temperature corresponding to the average crystallite size in samples 1, 2 and 3, are 578.17 ± 0.04, 578.28 ± 0.03 and 578.38 ± 0.02°C, respectively. For the cubic to monoclinic transformation, the corresponding onset temperatures for the same three samples, are 577.90 ± 0.02, 577.84 ± 0.02 and 577.78 ± 0.02°C. These are believed to represent the end temperatures of undercooling, just as nucleation of the new phase begins. Interphase curvature is such that the monoclinic phase is on the concave side of the interphase.

Appropriate coating methods and other conditions for enzyme-linked immunosorbent assay of smooth, rough, and neutral lipopolysaccharides of Pseudomonas aeruginosa.

Smooth, rough, and neutral forms of lipopolysaccharide (LPS) from Pseudomonas aeruginosa were used to assess the appropriate conditions for effective enzyme-linked immunosorbent assay (ELISA) of LPS. Each of these forms of well-defined LPS was tested for the efficiency of antigen coating by various methods as well as to identify an appropriate type of microtiter plate to use. For smooth LPS, the standard carbonate-bicarbonate buffer method was as efficient as the other sensitivity-enhancing plate-coating methods compared. The rough LPS, which has an overall hydrophobic characteristic, was shown to adhere effectively, regardless of the coating method used, to only one type of microtiter plate, CovaLink. This type of plate has secondary amine groups attached on its polystyrene surface by carbon chain spacers, which likely favors hydrophobic interactions between the rough LPS and the well surfaces. Dehydration methods were effective for coating microtiter plates with the neutral LPS examined, which is composed predominantly of a D-rhamnan. For the two dehydration procedures, LPS suspended in water or the organic solvent chloroform-ethanol was added directly to the wells, and the solvent was allowed to dehydrate or evaporate overnight. Precoating of plates with either polymyxin or poly-L-lysine did not give any major improvement in coating with the various forms of LPS. The possibility of using proteinase K- and sodium dodecyl sulfate-treated LPS preparations for ELISAs was also investigated. Smooth LPS prepared by this method was as effective in ELISA as LPS prepared by the hot water-phenol method, while the rough and neutral LPSs prepared this way were not satisfactory for ELISA.

Condensation reactions of activated picolines with anthranilate esters and o‐nitrobenzaldehyde: Improved syntheses of the antiarrhythmic drug encainide

AbstractTwo new and improved syntheses of the antiarrhythmic drug Encainide, 1, are presented. The first approach is based on the condensation of 2‐picolyllithium with the p‐anisoyl amide of methyl anthranilate, 3, followed by a series of catalytic hydrogenations and methylation. The second route relies on a particularly facile condensation reaction between N‐methylpicolinium methyl sulfate and o‐nitrobenzaldehyde to produce the alcohol 17c in high yield which is converted to the olefin 18c by a novel dehydration procedure and then to the final molecule, by catalytic hydrogenation over platinum followed by acylation.