Scanning electron microscopy最新文献

The relationship of polyploidization (DNA content) to differentiation is not well defined. We have developed centrifugal elutriation and Percoll density gradient centrifugation to obtain large numbers of highly-purified megakaryocytes which subsequently were stained for DNA content with Hoechst 33342 and sorted by FACS into 8C, 16C and 32C ploidy classes for correlated analysis of cell surface structures by scanning electron microscopy. Each ploidy class revealed unique surface characteristics that reflect differentiation occurring in megakaryocytes independent of their DNA content.

The enamel ultrastructure of multituberculate mammals has been sampled extensively and studied intensively and is better known than for any other group of early mammals. The enamel of the earliest multituberculates, those of the Late Triassic-Early Jurassic suborder Haramiyoidea and the Late Jurassic-early Early Cretaceous suborder Plagiaulacoidea, is "preprismatic." With only two exceptions, all Late Cretaceous and early Tertiary genera of multituberculates examined have prismatic enamel. Prisms are either small with circular (complete) boundaries or large with arc-shaped (incomplete) boundaries. There is a remarkably consistent relationship between enamel ultrastructural type and subordinal taxa in that small, circular prisms are usually found within the suborder Ptilodontoidea and large, arc-shaped prisms are usually found in the suborder Taeniolabidoidea and in six Late Cretaceous-Early Tertiary genera of indeterminate subordinal status. Research currently in progress suggests that both small, circular prisms and large, arc-shaped prisms are homologous in all multituberculates in which they occur, with one exception. Neoliotomus, a taeniolabidoid, appears to have evolved small, circular prisms independently. In addition, it appears that large, arc-shaped prisms represent the primitive condition in multituberculates with prismatic enamel, not small, circular prisms as has been proposed previously.

The intracellular structure of the outer hair cells of the normal guinea pig organ of Corti was investigated three dimensionally by scanning electron microscope. Freeze fracturing technique followed by maceration with a 0.1% OsO4 solution (osmic maceration method) was used. Among the cell organelles, the endoplasmic reticulum (ER) showed the most interesting features, such as subsurface cisternae and lamellar bodies. The subsurface cisterna which formed a stratiform network covered the inner surface of the cell membrane and the stratiform structure disappeared at the infranuclear region. Variously shaped mitochondria (spherical, cylindrical and branched) were found on the innermost layer of the subsurface cisterna. The lamellar body which was located beneath the cuticular plate consisted of dilated cisternae and tubular ER and was surrounded by mitochondria. The tubular ER of the lamellar body were continuous with the subsurface cisterna.

The events involved in the histogenesis of the primitive nervous system involve precise control over cell shape changes, cellular migrations, cell-cell and cell-extracellular matrix interactions. The coordinated procession of these events results in the elevation of the neural folds, and their apposition and fusion in the dorsal midline, forming the primary neural tube. This is followed by a second series of cellular migrations and rearrangements (collectively called secondary neurulation) which result in lengthening of the caudal neural tube. After a brief consideration of the mechanisms involved in neurulation, the effects of gene or teratogen induced perturbations of these events are presented and reviewed. New data are presented on neurulation in the delayed Splotch mutant embryo and on the effects of altering mesenchymal or neuroepithelial basal lamina constituents on primary and secondary neurulation.

Morphometrical and X-ray elemental information was extracted from Scanning Transmission Electron Microscopy (STEM) images of hepatic lysosomes of a patient with idiopathic hemosiderosis before and after treatment by phlebotomy. The elements of interest were iron, stored in pathological quantities in hepatic lysosomal structures and cerium, used as a capture ion after a cytochemical reaction to detect acid phosphatase activity in the lysosomal structures. Morphologically the lysosomal structures are heteromorph and the elements iron and cerium are heterogeneously distributed. With "reduced raster" (= reduced scanning area) analysis at 16 X 16 pixelpoints (integrating image and X-ray microanalysis), a marked difference in the area of the cross sectioned lysosomal structures before and after treatment could be demonstrated. Simultaneously the difference in the relative orientation of the elements iron and cerium before and after phlebotomy could be visualized. Chelex ion exchange beads, loaded with 11.5% w/w iron, and coembedded with the tissue blocks, were used as an internal standard. A mean iron peak to background ratio was obtained and a factor, converting ratio to absolute iron concentration, was calculated. The same calculation procedure, now per pixelpoint, was followed for the hepatic lysosomal structures. A marked difference in iron concentration in the individual lysosomal structures was observed before and after treatment by phlebotomy.

Cells from Xenopus laevis blastulae have a poorly developed ability to adhere to Sepharose beads covalently coupled to bovine plasma fibronectin (FN-beads). They do, however, have the ability to adhere to con A-beads and cytodex-1 and cytodex-3 beads. Beginning at the early gastrula stage, there is a progressively increasing ability of cells to adhere to FN-beads. Gastrula cells adhere to FN-beads by the formation of large ruffling lamellipodia. These cells can translocate on the surface of FN-beads; and when attached to both beads and the surrounding glass substratum of culture vessels, have the ability to move the beads extensively. Gastrula cells also have the ability to adhere to but not move upon con A-beads, wheat germ agglutinin-beads, and soy bean agglutinin-beads. They do not adhere significantly to Tetragonolobus purpureas agglutinin-beads. These results suggest that there are increasing numbers of fibronectin receptors present on the surface of embryonic amphibian cells during the period of gastrulation. They may explain the differential distribution of fibronectin-containing fibrils in vivo as observed by scanning electron microscopy.

The phase changes calcium oxalate trihydrate-weddellite, weddellite-calcium oxalate monohydrate and calcium oxalate trihydrate-whewellite are individually examined at the atomic level from a theoretical point of view; concomitantly the topological requirements necessary for phase stability are clarified for each structure type. In solution a sequential series of phase transitions according to the steps calcium oxalate trihydrate-weddellite-whewellite is not likely to be energetically favoured; direct conversion of calcium oxalate trihydrate to whewellite should be, instead, ordinarily expected. It is formally demonstrated that along two axial directions a set of atoms is in essentially identical positions in both weddellite and whewellite. This notwithstanding, it is concluded that epitactic catalysis cannot and should not be considered a common mechanism for the formation of whewellite from weddellite (and vice versa) or of kidney stones in general.

This paper summarizes our studies of IUD-related disease with those previously published by others. Our data are based upon 51 IUDs and 42 index cases of IUD-related disease demonstrating specific processes. Gross, dissecting microscope, scanning electron microscope and X-ray microanalysis examinations were made of selected IUDs and associated tissues. Tissue associated with the IUDs revealed inflammation in 59.4%, calcific material in 6.3% and no abnormality in 34.4%. IUD-associated tissue responses were accompanied by changes of the IUD; these changes involved deposition of substances upon the IUD surface and degradation of the IUD itself. Disintegration of the IUD, its string or both, has been repeatedly observed. The material deposited upon the surface of the IUD included proteins and calcium salts. The changes which involve the IUD and the host appear to be operative in the genesis of IUD-related disease. Inflammatory changes and infections are the most common IUD-related disease processes and are also the mechanisms commonly associated with the most serious complications of IUD use, reproductive failure and death. We propose that serious IUD-related disease is caused by or is a direct consequence of processes which alter the IUD and which potentiate inflammation and infection. A model amenable to testing is proposed.

The improvement in scanning electron microscopy (SEM) techniques has permitted us to describe the microstructure of the liver. By SEM, the liver peritoneal surface is composed of flat mesothelial cells possessing microvilli and cilia. Hepatic sinusoids connect the portal vessels with the terminal branches of the hepatic vein (central veins). Endothelial cells of the portal space arteries are elongated and arranged longitudinally, while those of the central and portal veins are polygonal and flattened, possessing microvilli. The sinusoidal endothelial cells show both small fenestrations (sieve plates), up to 200 nm in diameter, and large ones, up to 1 micron. Within the sinusoids are seen bridging structures, covered by fenestrated endothelium, seeming to have a fibrillar core. Kupffer cells resemble macrophages, showing microvilli, blebs, lamellipodia and filopodia. Within the Space of Disse are seen the fat-storing cells, having laminar dendritic projections. The polyhedral liver cell faces the Space of Disse (vascular pole) or faces an adjacent hepatocyte (biliary pole). Vascular facets are evenly covered by microvilli. Biliary facets show a central longitudinal depression, bordered by microvilli (bile hemicanaliculi). Canaliculoductular junction and bile duct epithelia show blebs, microvilli and cilia. Up to now, fetal liver and liver pathology have been scarcely investigated by SEM: in the future, they can be successfully approached by three-dimensional studies.

High magnification studies of the fenestrated capillary endothelium in the zona fasciculata (ZF) of rat adrenal glands were performed using the objective lens stage of an analytical scanning electron microscope (SEM) equipped with a lanthanum hexaboride emitter (LaB6). Resolution of surface substructure of the luminal membrane obtained with specimens decorated with gold/palladium (Au/Pd) was compared with that observed in others sputter coated with tantalum (Ta). High magnification (50,000x) of the fenestrated endothelium demonstrates that tantalum coating of the cryofractured adrenals improves the substructural detail compared to that seen in Au/Pd decorated specimens. The procedures used in specimen preparation, metal deposition and secondary electron imaging (SEI) are described. Quality imaging achieved using the objective lens stage is a result of the elimination of the SE-III component derived from backscattered electrons. Rat adrenals exhibited uniformly patent capillaries. High magnification micrographs of capillary walls were randomly recorded in two morphometric studies of the fenestral content of capillaries in the rat adrenal cortex. Adrenocorticotropic hormone (ACTH), when administered to rats following dexamethasone (DEX) treatment, significantly reduced the fenestrae/micron 2 of endothelial surface and increased the mean size of fenestrae. After hypophysectomy, the number of fenestrae/micron 2 declined over 48 h; within 2 h after ACTH was given to rats hypophysectomized 48 hours earlier, the fenestrae/micron 2 had increased two-fold. These studies indicate that ACTH plays an important role in modulating fenestral content of the capillary endothelium in the adrenal cortex.