Scanning electron microscopy最新文献

Energy dispersive X-ray microanalysis in STEM (scanning transmission electron microscope) of freeze-dried cryosections from biological cells provides information on the subcellular element distribution in terms of dry weight concentration. The local dry weight content in the range of 5-50%, respectively the local water content within 50 to 95%, in different subcellular compartments can be determined by measuring the darkfield intensity by means of an annular detector in STEM. Calibration is done by measuring the darkfield intensity of similarly prepared cryosections from dextran-water-solutions in varying concentration. Thus, by combining the X-ray microanalytical data evaluated by the continuum method with the STEM darkfield values, wet weight concentrations of elements in subcellular compartments are obtained. The method was applied to fibroblast cells in suspension. The reliability of this method is compared with other techniques to measure mass and intracellular water by electron microscope methods.

The most frequently used resins for vascular corrosion casting Mercox Cl-2B, Mercox Cl-2B diluted with methylmethacrylate (MMA) monomer and various self prepared MMA and hydroxypropyl-methacrylate mixtures were tested with regard to their thermostability, shrinkage, viscosity and replication quality. It was found that tempering of the plastics improves their thermostability with the exception of Mercox Cl-2B and that shrinkage depends on the amount of monomers a resin contains. In detail; Mercox Cl-2B has the lowest shrinkage (8.018%) whereas a hydroxypropyl-methacrylate mixture possessed the highest (20.408%). But, on the other hand, viscosity decreases with the quantity of monomers. All resins tested were able to replicate structures of 260 nm height but the resins' quality of replication was found to be limited by the effects of shrinkage. Finally, a method to estimate the blood volume of organs and tissues with the help of vascular corrosion casts is given.

Acute duodenal ulcers are produced in mice as a remote ("abscopal") effect of irradiation to the lower mediastinum. Such lesions have been examined with scanning electron microscopy at 5, 8 and 28 days after irradiation with 18 Gy of X-rays. All the ulcers occur within the first 1 cm long segment of the duodenum which is endowed with Brunner's glands. The single lesions vary in size, shape and position. The damaged area often includes much of the duodenal circumference and is distinguished by conical or rudimentary villi, or even by the complete absence of villi. In contrast, around the periphery of the ulcer the villi are mostly vertical. Although the floor of these lesions appears to be covered with a continuous epithelial layer, during the first 4 weeks after irradiation the severity of the focal duodenal damage seems to increase gradually with time. The lesions have been compared with specimens from unirradiated mice and also with samples taken 3 days after partial thoracic irradiation when little damage is seen. The pattern of fully developed duodenal lesions differs greatly from that seen after direct irradiation where damage has not included localised ulceration in the samples of jejunum so far examined. The lesions induced by partial thoracic irradiation may be related to radiation injury to vascular or autonomic nerve targets in the lower mediastinum. Such injury could result in malfunction of the pyloric sphincter or could alter the secretion by Brunner's glands and thus lead to duodenal ulceration.

Established systems of long-term bone marrow culture (LTBMC) have contributed to our understanding of the interrelationships between the adherent stromal cells and the stem cells, committed progenitors and mature terminally differentiated cells. While cell-mediated or short range stromal interactions appear to be a major source of homeostatic control between the stromal microenvironment and the stem cells, positive and negative humoral influences or long-range mechanisms also regulate stem cell proliferation and differentiation. Adherent stromal conditioned medium generates factors which can trigger CFU-s into DNA synthesis within 18 hours or inhibit incorporation of tritiated thymidine into rapidly proliferating CFU-s. Other adherent stromal factors reduce proliferation and terminal erythroid differentiation of BFU-e. Stromal cells also produce a synergistic activity which stimulates formation of giant macrophage colonies in conjunction with CSF. Continued examination of these factors should lead to better understanding of the mechanisms involved in control of hematopoietic stem cell proliferation and differentiation.

Structural features of isolated, fractionated rat bone marrow endothelium were compared to those of marrow sinus endothelium in situ. Marrow endothelium was purified, first by density gradient sedimentation on Percoll and then subjected to centrifugal elutriation. Using antifactor VIII antibody staining (indirect immunofluorescent method), preparations of greater than 50% purified endothelium were obtained. By SEM, these cells were about 10 microns in size and showed smooth surface and numerous invaginations. These features were also observed in the in situ endothelium obtained by perfusion-fixation and freeze-cracking. In addition, in situ endothelium displayed numerous hemopoietic cells in migration through the endothelium. By TEM, isolated endothelium showed numerous vesiculations, giving the cell sponge-like appearance. This corresponded to numerous intracellular vesicles in sinus endothelium in situ, reflecting high magnitude of fluid and molecular transport across the endothelium. Weibel-Palade bodies were not seen in either form of the endothelium, despite the positive reaction for factor VIII-related antigen. This finding suggested that the cell, while possessing factor VIII-related antigen, does not store this protein.

The assessment of in vitro osteoclastic activity has, until recently, been dependent on the analysis of organ culture experiments. We have developed a single cell resorption assay so that the resorptive function of individual osteoclasts could be studied. This paper examines the biological variation in the sizes of resorption lacunae produced by bone cell cultures derived from neonate rats and rabbits, and prehatch or hatchling chicks. Cultures were run for 24h for all species; and in addition for 48h for rat, 9 or 12 hours for rabbit and 3-7 hours for chick. The numbers of the nuclei of osteoclasts seeded on to plastic were counted for all three species. SEM stereophotogrammetry was used to measure areas, volumes, and maximum and average depths of the lacunae using specially designed instruments and software. Rat osteoclasts were smallest, and more chick osteoclasts were very large. There was a species difference in the onset of resorption and the sizes of pits produced, the chick osteoclasts being more vigorous resorbers than the rabbit ones, and the rat least so. For a given plan area, chick lacunae were deeper. There was a high correlation between area and volume. The range of maximum depths for a given area was high, however. Thus the mean of a few measurements of depths should not be used to calculate volume from area. At 24 hours, 77% of the rat, 47% of the rabbit and 28% of the chick lacunae were less than 1,000 microns 3 in volume; and 11% of the rat, 17% of the rabbit and 22% of the chick lacunae were between 1,000 and 2,000 microns 3 in volume. The mean values at 24 hours were 981, 2796, and 4582 microns 3 for rat, rabbit and chick lacunae respectively.

Embryos of C57B1/6J mice were examined grossly, and by light and scanning electron microscopy on days 8 through 19 of gestation. Adult eyes were examined by slit lamp biomicroscopy and light microscopy. A spontaneous incidence of eye malformations including microphthalmia, microphakia, corneal opacity and anterior segment dysgenesis was observed at a rate of 13.2% in the adults and 10.8% in the day 14 embryos. Scanning electron microscopy demonstrates the complex series of coordinated changes in shape and tissue interrelationships observed in normal ocular development. Possible routes of abnormal ocular morphogenesis beginning as early as the time of optic vesicle formation are discussed.

Densely ionizing, particulate radiations in outer space are likely to cause to mammalian tissues biological damage that is particularly amenable to examination by the techniques of electron microscopy. This situation arises primarily from the fact that once the density of ionization along the particle track exceeds a certain value, small discrete lesions involving many adjacent cells may be caused in organized tissues. Tissue damage produced by ionization densities below the critical value also afford opportunities for electron microscopic evaluation, as is shown by the damage produced in optic and proximate tissues of the New Zealand white rabbit in terrestrial experiments. Late radiation sequelae in nondividing, or terminally differentiating, tissues, and in stem cell populations, are of special importance in these regards. It is probable that evaluations of the hazards posed to astronauts by galactic particulate radiations during prolonged missions in outer space will not be complete without adequate electron microscopic evaluation of the damage those radiations cause to organized tissues.

Scanning electron microscope (SEM) morphological analysis combined with energy dispersive characteristic x-ray analysis provides insight into the mechanism of biological mineralization. A time series of tissue micrographs and mineralization measurements can permit the determination of the mineralization kinetic behavior and is the basis upon which a computer model has been devised. The computer model is constructed from fundamental principles of crystal nucleation and precipitation theory. Various general forms of the model are tested against the laboratory data for goodness-of-fit using the least squares method, and two models are found to be acceptable. Both of the acceptable models involve inhibition of the mineralization process which has a reaction order ranging from one to two. A third model involving constant nucleation rate must be rejected. Having established working first principle models for the mineralization process, one can compute a constant number of nucleation sites and a supersaturation value for calcium in various mineralized tissues such as the spongiosa and fibrosa of heart valve leaflet implants. These quantities are determined and used in discussing a general theory for biomineralization which emphasizes therapeutic considerations.

Past scanning electron microscopy (SEM) reports demonstrated cell surface undulations, ridges, folds, and ruffles to support the monocytic/histiocytic nature of hairy-cell leukemia (HCL) cells. On the other hand, SEM studies illustrating spikes, villi, and microvilli on the cell surfaces favored the lymphocytic nature of hairy cells (HCs). The evidence for the 'hybrid' nature of the HCs has emerged from the demonstration of concurrent display of monocytic (ruffles) and lymphocytic (microvilli) surface features on each cell. Utilizing improved methods of sampling, fixation, and drying, the current status is that all HCs display microvilli and ruffles simultaneously. However, two distinct morphological types of HCs are acknowledged: cells showing ruffled areas next to clumps of microvilli (type A), and cells displaying microvilli interspersed among ruffles (type B). Each of the HCL cases reported in our studies had cells with either type A or type B surface features. Amazingly, these unique SEM features correlate well with the prevalent trend to classify HCs as malignant (villous) B-lymphocytes imitating (ruffled) monocytes in some functional respects.