Chemical and bacteriological composition of granular methanogenic sludge

1985 ◽  
Vol 31 (8) ◽  
pp. 744-750 ◽  
Author(s):  
J. Dolfing ◽  
A. Griffioen ◽  
A. R. W. van Neerven ◽  
L. P. T. M. Zevenhuizen
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Buoyant Density ◽  
Extraction Methods ◽  
Drying Methods ◽  
Extracellular Material ◽  
Extracellular Polymers ◽  
Intact Cells ◽  
Critical Point Drying ◽  
Scanning Electron

Methanogenic sludge granules grown on waste water from a sugar refinery consisted of several bacterial morphotypes embedded in a matrix of extracellular material. Comparison of critical point drying and freeze-drying methods for preparing samples for scanning electron microscopy to determine the presence of extracellular material indicated that the former method permitted observations of extracellular material and intact cells. The effects of different extraction methods used for isolation of these extracellular polymers was also investigated by scanning electron microscopy. Of the various extraction procedures (EDTA, NaOH, autoclaving, water–phenol), water–phenol left most of the cells intact and was found to be a very efficient method of extraction. Extracellular polymers equivalent to 10–20 mg hexose/g of granules were extracted. The high resistance of the granules against disintegration by various chemical methods suggested that different extracellular polymers and probably different groups of organisms contributed to the matrix in which the bacteria were embedded. The chemical composition of the granules did not differ from the composition of bacteria in general. The buoyant density of 1.00–1.05 g∙g−1of the granules indicated that a simple agglomeration was the mechanism by which these methanogenic consortia improved their settling characteristics.

Alternative Method of Rapid Drying Vascular Specimens for Scanning Electron Microscopy

2003 ◽  
Vol 10 (2) ◽  
pp. 285-287 ◽  
Author(s):  
DáŠa Slížová ◽  
Otakar Krs ◽  
Blanka PospíŠilová
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Micrographs ◽  
Low Cost ◽  
High Rate ◽  
Drying Methods ◽  
Scanning Electron Micrographs ◽  
Air Drying ◽  
Critical Point Drying ◽  
Scanning Electron

Purpose: To report the use of hexamethyldisilazane (HMDS) as an alternative to critical point drying for preparing stented canine peripheral vessels for scanning electron microscopy (SEM). Technique: Vascular specimens were fixed in 4% formaldehyde overnight, dehydrated in a graded ethanol series, followed by immersion in 100% hexamethyldisilazane. After air drying, the specimens were mounted on stainless steel stubs, coated with gold, and examined in the SEM. The electron micrographs were of high quality, showing the layers of the vascular wall and the incorporated stent covered by a neointimal layer. The micrographs were comparable to corresponding histological sections, but detailed endothelial patterns were more visible. Conclusions: HMDS treatment and subsequent air drying provides good quality scanning electron micrographs that reveal both endothelial patterns and the layered architecture of stented vessels. The disadvantage of HMDS drying may be a shrinkage and distortion similar to other drying agents. Ease of handling, low cost, and a high rate of success are advantages that favor HMDS desiccation over other drying methods.

scholarly journals Scanning electron microscopy preparation and analysis of the cell cortex ultrastructure

2020 ◽  
Author(s):  
D. Flormann ◽  
M. Schu ◽  
E. Terriac ◽  
M. Koch ◽  
S. Paschke ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Critical Point ◽  
Structural Defects ◽  
Cell Cortex ◽  
Drying Methods ◽  
Actin Network ◽  
Actin Cortex ◽  
Critical Point Drying ◽  
Scanning Electron

AbstractThe cellular cortex is a 200-nm-thick actin network that lies beneath the cell membrane. It is responsible for the mechanical properties of the cell and is involved in many cellular processes, such as cell migration and interactions with the environment. To develop a clear view of the structure of this meshwork, high resolution imaging is essential, such as electron microscopy. This technique requires complex sample preparation that can lead to artifacts like shrinkage or hole formation. We present a preparation method that reduces artifacts significantly. Here, the final drying step that is typically performed by critical point drying is replaced by hexamethyldisilazane drying. We quantitatively investigated sample integrity after both preparation methods, and show that there are significant advantages of hexamethyldisilazane drying compared to critical point drying. Furthermore, automated analysis of a network is classically performed by thresholding-based software programs, which are sensitive to noise and uneven brightness of images. The here presented analysis that we have developed is based on a vectorial node algorithm. It reproduces all kinds of networks sufficiently to allow derivation of quantitative network-specific parameters, such as mesh hole size. We use this analysis to compare the network structure of cells prepared by these two drying methods, and show that hexamethyldisilazane drying leads to fewer artificial mesh holes compared to critical point drying. We thus present here a significantly improved method to quantitatively investigate the actin cortex of cells, and show that hexamethyldisilazane drying leads to more accurate imaging compared to critical point drying.Insight BoxThe highest resolution for imaging the cellular actin cortex is provided by electron microscopy. Scanning electron microscopy samples require a drying process, usually achieved by critical point drying, which is critical for the sample integrity. We compare the structural defects in the actin cortex of hTert RPE1 cells after critical point drying and a chemical based method, namely hexamethyldisilazane drying. In order to characterize the actin network, we also developed a new vectorial based tracing software. We bring here new tool, both experimental and analytical, which will help to streamline studies of the actin cortex.

Preservation of Plant Cell Surfaces For Scanning Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 472-473
Author(s):  
Linda M. Sicko ◽  
Thomas E. Jensen
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Critical Point ◽  
Filter Paper ◽  
Freeze Drying ◽  
Cell Surfaces ◽  
Air Drying ◽  
Popular Method ◽  
Critical Point Drying ◽  
Scanning Electron

The use of critical point drying is rapidly becoming a popular method of preparing biological samples for scanning electron microscopy. The procedure is rapid, and produces consistent results with a variety of samples. The preservation of surface details is much greater than that of air drying, and the procedure is less complicated than that of freeze drying. This paper will present results comparing conventional air-drying of plant specimens to critical point drying, both of fixed and unfixed material. The preservation of delicate structures which are easily damaged in processing and the use of filter paper as a vehicle for drying will be discussed.

Development of the Foramen Secundum in the Chick as Observed by Scanning Electron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 212-213
Author(s):  
M.J.C. Hendrix ◽  
D.E. Morse
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Procaine Hydrochloride ◽  
Cardiac Anomaly ◽  
Chick Embryos ◽  
Congenital Cardiac Anomaly ◽  
Septal Defects ◽  
Critical Point Drying ◽  
Scanning Electron

Atrial septal defects are considered the most common congenital cardiac anomaly occurring in humans. In studying the normal sequential development of the atrial septum, chick embryos of the White Leghorn strain were prepared for scanning electron microscopy and the results were then extrapolated to the human heart. One-hundred-eighty chick embryos from 2 to 21 days of age were removed from their shells and immersed in cold cacodylate-buffered aldehyde fixative . Twenty-four embryos through the first week post-hatching were perfused in vivo using cold cacodylate-buffered aldehyde fixative with procaine hydrochloride. The hearts were immediately dissected free and remained in the fixative a minimum of 2 hours. In most cases, the lateral atrial walls were removed during this period. The tissues were then dehydrated using a series of ascending grades of ethanol; final dehydration of the tissues was achieved via the critical point drying method followed by sputter-coating with goldpalladium.

Intracellular structures of rapid frozen biological samples observed by high-resolution low-temperature Scanning Electron Microscopy

1989 ◽  
Vol 47 ◽  
pp. 736-737
Author(s):  
T. Inoué ◽  
H. Koike
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Liquid Nitrogen ◽  
Specimen Preparation ◽  
Chemical Fixation ◽  
Brown Adipose ◽  
Critical Point Drying ◽  
Temperature Scanning ◽  
Scanning Electron

Low temperature scanning electron microscopy (LTSEM) is useful to avoid artifacts such as deformation and extraction, because specimens are not subjected to chemical fixation, dehydration and critical-point drying. Since Echlin et al developed a LTSEM, many techniques and instruments have been reported for observing frozen materials. However, intracellular structures such as mitochondria and endoplasmic reticulum have been unobservable by the method because of the low resolving power and inadequate specimen preparation methods. Recently, we developed a low temperature SEM that attained high resolutions. In this study, we introduce highly magnified images obtained by the newly developed LTSEM, especially intracellular structures which have been rapidly frozen without chemical fixation.[Specimen preparations] Mouse pancreas and brown adipose tissues (BAT) were used as materials. After the tissues were removed and cut into small pieces, the specimen was placed on a cryo-tip and rapidly frozen in liquid propane using a rapid freezing apparatus (Eiko Engineering Co. Ltd., Japan). After the tips were mounted on the specimen stage of a precooled cryo-holder, the surface of the specimen was manually fractured by a razor blade in liquid nitrogen. The cryo-holder was then inserted into the specimen chamber of the SEM (ISI DS-130), and specimens were observed at the accelerating voltages of 5-8 kV. At first the surface was slightly covered with frost, but intracellular structures were gradually revealed as the frost began to sublimate. Gold was then coated on the specimen surface while tilting the holder at 45-90°. The holder was connected to a liquid nitrogen reservoir by means of a copper braid to maintain low temperature.

Criteria for the evaluation of low-temperature Scanning Electron Microscopy

1986 ◽  
Vol 44 ◽  
pp. 902-903
Author(s):  
Alan Beckett
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Conformational Changes ◽  
Chemical Vapour ◽  
List Type ◽  
Dimensional Changes ◽  
Critical Point Drying ◽  
Temperature Scanning ◽  
Scanning Electron

Low temperature scanning electron microscopy (LTSEM) has been evaluated with special reference to its application to the study of morphology and development in microorganisms. A number of criteria have been considered and have proved valuable in assessing the standard of results achieved. To further aid our understanding of these results, it has been necessary to compare those obtained by LTSEM with those from more conventional preparatory procedures such as 1) chemical fixation, dehydration and critical point-drying; 2) freeze-drying with or without chemical vapour fixation before hand.The criteria used for assessing LTSEM for the above purposes are as follows: 1)Specimen immobilization and stabilization2)General preservation of external morphology3)General preservation of internal morphology4)Exposure to solvents5)Overall dimensional changes6)Cell surface texture7)Differential conformational changes8)Etching frozen-hydrated material9)Beam damage10)Specimen resolution11)Specimen life

Vergleich verschiedener Immun-Dekorationsmethoden für die Rasterelektronenmikroskopie am Beispiel eines Protein-Antigens auf der Oberfläche der Hefe Candida albicans/ A Comparison of Decoration Techniques for the Demonstration of Immunocomplexes by Scanning Electron Microscopy: Labeling of a Protein Antigen on the Surface of the Yeast Candida albicans

1985 ◽  
Vol 40 (7-8) ◽  
pp. 539-550 ◽  
Author(s):  
Margarete Borg
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Candida Albicans ◽  
Protein A ◽  
Peritoneal Macrophages ◽  
Polystyrene Latex ◽  
Target Antigen ◽  
Protein Antigens ◽  
Critical Point Drying ◽  
Scanning Electron

Abstract The labeling of immunocomplexes for scanning electron microscopy (SEM) is a fairly new technique, and the various procedures, that have been proposed, have not yet been compared. Such comparative evaluation was performed with Candida protease as a target antigen. This secretory enzyme of the opportunistic yeast Candida albicans can be localized on the surface of fungal blastopores and mycelia, both after growth in proteinaceous medium and upon infection of murine peritoneal macrophages. The presence of the protease antigen was confirmed by immunofluorescence and by immunoperoxidase-light microscopy. The decoration of protease - anti protease complexes for SEM was attempted with colloids derived from the immunoperoxidase reaction, by the immunogold technique, and by antibodies linked to beads of synthetic polymers (polystyrene, polymethacrylate, polyacrolein). In addition, inactivated Staphylococcus aureus was used, which binds to antibodies through its protein-A. The high resolution by SEM of surface structures was matched only by the colloid based decoration techniques. All conjugates with beads suffered from inconsistent binding, which did not correspond with the distribution of the surface antigen. The comparatively best result with beads was obtained with polystyrene (Latex). Colloid based techniques in addition allow for critical point drying, which cannot be applied to synthetic beads in the usual manner.

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