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At least 523 records · Page 29Linked to original sources
PubMed1993

High-resolution visualization by field emission scanning electron microscopy of Enterococcus faecalis surface proteins encoded by the pheromone-inducible conjugative plasmid pCF10.

Enterococcus faecalis can acquire antibiotic resistance and virulence genes by transfer of pheromone-inducible conjugative plasmids such as pCF10, which encodes tetracycline resistance. Two pCF10-encoded cell surface proteins, Sec10 and Asc10, have been previously shown to play an important role in the transfer of this plasmid. We used high-resolution, field emission scanning electron microscopy to visualize these proteins on the surfaces of a series of isogenic strains of E. faecalis. Immunogold labeling, using both 6- and 12-nm colloidal gold, unambiguously demonstrated the expression and distribution of Sec10 and Asc10 on the surface of the E. faecalis cells. On unlabeled E. faecalis cells which expressed either Sec10 or Asc10, the former appeared to be more readily detected. Immunogold labeling of E. faecalis cells expressing both Asc10 and Sec10 clearly demonstrated the abundance and intermixing of both proteins on the cell surface except at septal regions. Sec10 was observed to be distributed over the cell surface. At regions of cell-cell contact, fine strands representing Asc10 were observed directly attaching adjacent cells to one another.

Antibodies, Monoclonal↗
PubMed1980

Chemical and enzymatic changes in the cell walls of Candida albicans and Saccharomyces cerevisiae by scanning electron microscopy.

Candida albicans and Saccharomyces cerevisiae cells were examined by scanning scanning electron microscopy before and after extraction of the mannans of the cell wall. The surfaces of control cells were smooth; after mannan extraction they were rough and showed erosions which were particularly striking within the area of the scars. Helicase digested irregular holes through the cell wall within 20 min; these increased in size during an additional 40 min of digestion. These holes were not localized in or on the bud scars, which remained intact even after the long digestion period. The results were used to construct a model for yeast cell wall structure.

Candida albicans↗
PubMed1999

Quality assessment of atomic force microscopy probes by scanning electron microscopy: correlation of tip structure with rendered images.

While image quality from instruments such as electron microscopes, light microscopes, and confocal laser scanning microscopes is mostly influenced by the alignment of optical train components, the atomic force microscope differs in that image quality is highly dependent upon a consumable component, the scanning probe. Although many types of scanning probes are commercially available, specific configurations and styles are generally recommended for specific applications. For instance, in our area of interest, tapping mode imaging of biological constituents in fluid, double ended, oxide-sharpened pyramidal silicon nitride probes are most often employed. These cantilevers contain four differently sized probes; thick- and thin-legged 100 microm long and thick- and thin-legged 200 microm long, with only one probe used per cantilever. In a recent investigation [Taatjes et al. (1997) Cell Biol. Int. 21:715-726], we used the scanning electron microscope to modify the oxide-sharpened pyramidal probe by creating an electron beam deposited tip with a higher aspect ratio than unmodified tips. Placing the probes in the scanning electron microscope for modification prompted us to begin to examine the probes for defects both before and after use with the atomic force microscope. The most frequently encountered defect was a mis-centered probe, or a probe hanging off the end of the cantilever. If we had difficulty imaging with a probe, we would examine the probe in the scanning electron microscope to determine if any defects were present, or if the tip had become contaminated during scanning. Moreover, we observed that electron beam deposited tips were blunted by the act of scanning a hard specimen, such as colloidal gold with the atomic force microscope. We also present a mathematical geometric model for deducing the interaction between an electron beam deposited tip and either a spherical or elliptical specimen. Examination of probes in the scanning electron microscope may assist in interpreting images generated by the atomic force microscope.

DNA↗
PubMed1991

Polymorphic behavior of sprayed lipid micropellets and its evaluation by differential scanning calorimetry and scanning electron microscopy.

Considering the importance of polymorphism occurring in solid dosage forms causing instability, the polymorphic behavior of spray-dried and -congealed lipid micropellets was examined by differential scanning calorimetry and scanning electron microscopy. The results showed that both of the spraying processes exert an important effect on their polymorphic and crystallization properties. In spray-drying, due to the rapid solvent evaporation, the obtained lipid micropellets possess an unstable polymorphic form. This unstable form transforms gradually toward a stable form by storage at elevated temperatures. The same modifications were observed with spray-congealed lipid micropellets. The type of glyceride (composition, chain length), solvent and drugs (estradiol cypionate, medroxyprogesterone acetate) and, further, the presence of a stabilizing agent such as lecithin affect the polymorphic transition and its rate.

Calorimetry, Differential Scanning↗
PubMed1994

Particles found in lung and brain following subureteral injection of polytetrafluoroethylene paste are not teflon particles.

We injected 0.3 ml. of polytetrafluoroethylene paste (Polytef) behind the left submucosal ureter in 4 mini-pigs and 4 dogs, and 2 dogs and 2 mini-pigs underwent sham operation and acted as controls. Two mini-pigs were injected with 0.5 ml. polytetrafluoroethylene (Teflon) suspended in 50 ml. of normal saline into a peripheral vein and 2 dogs were injected with 0.5 ml. polytetrafluoroethylene into a bladder vein. In addition, 4 dogs were injected with 0.1 ml. polytetrafluoroethylene paste suspended in 20 ml. saline into the right carotid artery. The lungs and brain from half of the animals who had subureteral and intravascular injection of polytetrafluoroethylene paste as well as sham operated animals were dissolved in sodium hypochlorite solution. The resulting organ suspensions were then centrifuged and the smear preparations of the precipitate were examined by polarized light microscopy, scanning electron microscopy and x-ray microanalysis. Polytetrafluoroethylene paste suspended in saline acted as positive control for polytetrafluoroethylene particles. Lungs and brain from the remaining animals were fixed in formalin solution. The brain and lungs of animals who underwent subureteral injection with a minimal amount of polytetrafluoroethylene paste carefully placed in the submucosal plane showed no evidence of polytetrafluoroethylene on histological examination, polarized light microscopy, scanning electron microscopy and x-ray microanalysis.

Animals↗
PubMed2003

Scanning electron microscopy and atomic force microscopy imaging of solid lipid nanoparticles derived from amphiphilic cyclodextrins.

Scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been applied to the imagery of solid lipid nanoparticles (SLNs) formulated from an amphiphilic cyclodextrin, 2,3-di-o-alkanoyl-beta-cyclodextrin, beta-CD21C6. Comparison of the results shows that the vacuum drying technique used in sample preparation for SEM causes shrinkage in the size of the SLNs, whereas the deposition method used for AFM causes the SLNs to form small clusters. The hydrodynamic diameter determined from photon correlation spectroscopy (PCS) is 359+/-15 nm and the zeta potential is -25 mV.

Cyclodextrins↗
PubMed1989

Kinetic analysis of thymocyte attachment to thymus stromal cells in culture by using phase-contrast and scanning electron microscopy.

Direct cellular contact between thymocytes and thymus stromal cells within the thymus appears to contribute to the maturation of thymocytes. Thymocyte-stromal cell complexes, formed in vivo, have been isolated by others and postulated to play a role in T-cell differentiation. These previous studies have been hampered, however, by a time-consuming isolation procedure from which only small numbers of these complexes are recovered. We have examined a model to study thymocyte-stromal cell complexes in vitro in which thymocytes are added to primary cultures of thymus stromal cells. In the present study, we found that thymocytes were histotypically selective in their attachment to thymus stromal cells. We also investigated the kinetics of thymocyte attachment to these thymus stromal cells. Cultures were examined at selected time intervals from 5 min through 3 days of incubation. Thymocyte attachment to stromal cells was a biphasic interaction, with maximum surface attachment at 15 min of cocultivation, followed by migration of thymocytes into the cultures. Morphological studies were confirmed by using 3H-leucine-labeled thymocytes and liquid scintigraphy. With increased time in culture, thymocytes became amoeboid and migrated between the layers of stromal cells where thymocyte mitotic figures were seen at 4 and 8 hr. In some cases it appeared that stromal cells, which often grew two to three cell layers deep, played an active role in enclosing thymocytes within the cultures. Large numbers of viable thymocytes were observed in the cultures at 24 hr. The number of thymocytes then decreased progressively on days 2 and 3, when relatively few were found within the layers of the culture.

Animals↗
PubMed2005

A comparative study of the structure of human and murine greater omentum.

In humans, the greater omentum is a fatty peritoneal fold that extends from the greater curvature of the stomach to cover most abdominal organs. It performs many functions, which include acting as a reservoir of resident peritoneal inflammatory cells, a storage site for lipid, and a regulator of fluid exchange in and out of the peritoneal cavity. Most importantly, the omentum readily adheres to areas of inflammation and peritoneal damage, often leading to adhesion formation. Despite its clinical importance, the omentum remains an understudied organ, and discrepancies exist as to its exact morphology. This study uses a combination of phase contrast microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to elucidate the structure of the greater omentum of both human and mouse and determine whether it possesses a typical surface mesothelial cell lining similar to other serosa. Results indicated that both human and murine omenta were of similar structure and composed of two distinct types of tissue, one adipose-rich and the other translucent and membranous. The adipose-rich regions were well-vascularised and covered by a continuous mesothelial cell layer except at the sites of milky spots. In contrast, translucent areas were poorly vascularised and contained numerous fenestrations of varying size. The possible function and developmental origin of these gaps is unclear; however, their role in promoting omental adhesion formation and in the successful use of omental graft material is discussed.

Adipose Tissue↗
PubMed2004

Light and scanning electron microscopy of the miracidium of Echinostoma paraensei (Trematoda, Echinostomatidae).

Echinostoma paraensei was described 1967 by Lie and Basch. Recently its natural definitive host, the aquatic rodent Nectomys squamipes, endemic in Brazil, was identified. As most of the echinostomatids, this species presents a zoonotic potential. The morphology and topography of the E. paraensei miracidium obtained from adult worms collected from the natural definitive host N. squamipes is described by light and electron microscopy. The arrangement and the dimensions of the epidermal plates are given. The eyespots are composed by two pairs of lenses measuring 6.03 microm. SEM observations shows that the miracidium body is covered by cilia except at the terebratorium region and the presence of alpha-tubulin in the cilia of the larvae is first recorded by immunelabeling. Nineteen papilla-like structures arranged in three axes and four groups were observed at the terebratoriun, this structure is retractable, presenting folds and a corrugated surface with profiles of cytoplasmic expansions, forming network of anatomizing folds.

Animals↗