Scanning microscopy最新文献

Exposure to intense sound produces a well-defined "patch" lesion on the chick basilar papilla in which 30-35% of the short hair cells are lost. The present study compares various aspects of sensory hair bundle morphology on surviving hair cells in the patch lesion with hair bundles from matched locations on nonexposed control papilla immediately after removal from the exposure and 12-days post exposure. The height and thickness of the hairs, the total number of hairs in the bundle, the width of the bundle, and the area and perimeter of the apical surface of the hair cell were quantified from scanning electron microscope photomicrographs. An attempt was also made to determine if there was a consistent microstructure to the pattern of hair cell loss within the lesion area. Similar observations in 12-day recovered ears are also presented. The results indicated that stereocilia height increased and width decreased on surviving hair cells in the exposed ear. The width of the hair bundle, the hair cell surface area, and perimeter also decreased. However, the number of hairs per cell remained unchanged, and there was no evidence of any consistent organization to the hair cell loss within the patch across a number of specimens. These observations indicated that the hair bundles on short hair cells underwent changes as a consequence of intense sound exposure. The results after 12 days of recovery were complicated by developmental changes on the papilla and incomplete maturation of the newly regenerated hair cells. It remains to be seen whether these changes were the result of cell sampling in the sound-damaged ear or were due to true structural alterations within the sensory hairs themselves.

A morphological study of DNA repair and apoptotic patterns in relationship with cell cycle events was performed on murine erythroleukemia cells. The presence and distribution of DNA replicon sites were evaluated through the BrdU-anti BrdU immunofluorescence and immunogold techniques in light and electron microscopy. Different patterns of labelling and percentages of BrdU positive cells were observed depending on irradiation dose (up to 60 Gy) and time in post-irradiation culture (up to 24 hours). An enlargement of the S phase of the cell cycle was evidenced 18 hours post-irradiation as determined by flow cytometry analysis. The high resolution approach showed that, in spite of several morphological alterations, BrdU labelling was present even in cells displaying early and late apoptotic features.

In this report, we review data dealing with radiation effects on cartilage. More specifically, we emphasize on alterations caused in the extra-cellular cartilage matrix. Although radiation studies predominantly describe the effect on the structure of DNA and on the mitotic activity of cells, alterations caused by the effect on the non-mitotic activity can also be important. Cartilage, having an extracellular matrix composed of 2 major components, aggrecan and collagen, provides a good model to study this kind of radiation effects. The following topics concerning literature data are summarized: effects on the amount of matrix synthesized, effects on the activity of certain enzymes and effects on the structure and morphology of the matrix. Some new findings concerning the radiation effect on the size distribution of aggrecan-aggregate populations, de novo synthesized by chondrocyte cultures, either derived from calcifying or from non-calcifying cartilage, are given.

The effect of poly-L-aspartic acid (PA) on the crystal structure of calcium oxalate crystals grown after spontaneous nucleation was evaluated as a function of relative supersaturation and calcium:oxalate ratio in a buffered salt solution, with pH and ionic strength in the range of normal human urine. PA was used as a model for naturally occurring acidic urine proteins that have been shown to inhibit nucleation and growth of calcium oxalate crystals. The crystals grown were characterized by optical microscopy and X-ray powder diffraction. It was observed that calcium oxalate monohydrate was the preferred crystalline form in the absence of added PA, and it was the only crystalline form obtained at most conditions tested without PA. However, the presence of PA favored the formation of calcium oxalate dihydrate crystals, when present in adequate quantities. The quantity of PA required to affect this change in preferred crystal structure was increased at higher supersaturations and at lower calcium:oxalate ratios, exhibiting a non-linear dependence on both variables. PA was also shown to be a kinetic inhibitor of calcium oxalate dihydrate crystallization. Aspartic acid monomer was found to cause no change in the preferred structure of calcium oxalate monohydrate at mass concentrations well beyond those required with PA to obtain 100% calcium oxalate dihydrate, indicating the critical importance of the polymeric nature of PA for this effect on crystal structure.

A model is presented visualizing the events leading to calcium-salt, crystal- and stone-formation inside the nephron. For each nephron segment, handling of urine components relevant to stone formation is considered and urine composition determined. This information was applied to nucleation experiments simulating passage of urine through a nephron. The model and in vitro experiments suggest that within normal transit times for the respective nephron segments, particles of a hydroxyapatite-like material first form near the bend in the Loop of Henle of juxtamedullary nephrons. From there on, calcium oxalate particles start to appear: first dihydrate, then monohydrate. In the collecting duct system, particle size increases primarily due to crystal agglomeration. Several conclusions with clinical and experimental relevance can be drawn. An increase in urinary volume does not decrease the chance of crystal formation in the Loop of Henle, but does decrease passage time through the collecting ducts, and thus, the time allowed for large particle formation. A calcium load does not increase the risk for nucleation up to the distal tubule, but does increase the risk of large particle formation in the collecting ducts. An oxalate load increases the chance for nucleation throughout the nephron. For experiments simulating crystallization processes occurring inside the nephron, diluted urines should be used. They should be diluted 16 to 50 times for testing nucleation, 2 to 30 times for testing crystal growth, and 2 to 20 times for testing crystal agglomeration. Undiluted urines may be used to mimic conditions in the pelvis and the bladder.

Ultrastructural studies of the statocysts and touch-plates of graviceptors (rhopalia) of Aurelia ephyrae revealed that (1) touch-plate hair cells are present; and (2) cytoplasmic strands from the hair cell bases extend from the neurite plexus to touch similar strands from the lithocytes. This close association of hair cell neurites and statocysts may have important implications regarding the transmitting and processing of positional information with respect to the gravity vector. Graviceptors of ephyrae which developed while weightless in microgravity were compared with controls at the ultrastructural level. We found that hair cells of ephyrae which developed in microgravity had fewer lipid droplets in the large spaces near their bases as compared with 1 g controls. In the ephyrae from the first microgravity experiment, hair cells had more large apical vacuoles with filamentous content than were found in hair cells of ephyrae from the second experiment and controls. The neurite plexus and the network of cytoplasmic strands extending to the statocysts were not different in microgravity-developed ephyrae from controls. Behavioral differences in swimming and orienting in ephyrae in microgravity and controls (reported earlier) were not explained by morphological differences in the hair cells of the touch-plates or the statocysts, although functional differences apparently occurred.

The fundamental structure formed when genomic DNA is packaged by protamine in the human sperm nucleus still remains essentially unresolved. It is known that the binding of protamine, a small arginine-rich protein, to DNA generates a large dense, hydrophobic complex making the sperm chromatin structure difficult to study microscopically. To visualize the internal nuclear structures, isolated human sperm nuclei were swollen extensively in saline buffer using only a reducing agent. The nuclei were swollen during deposition onto coverglass and then imaged in the atomic force microscope (AFM). The two main results obtained from imaging individual well-spread nuclei indicate that native human sperm chromatin is: (1) particulate, consisting primarily of large nodular structures averaging 98 nm in diameter, and (2) also composed of smaller, nucleosome-like particles observed to form linear chains near the nuclear periphery. These two types of chromatin particles imaged by AFM are remarkably similar to other AFM measurements made on native and reconstituted sperm and somatic chromatin.

Energy dispersive X-ray microanalysis was performed on altogether 42 surgically removed tissue specimens of 32 patients, which were taken either from intact thyroid parts or various histopathologically verified tumors of the thyroid gland. The tissue specimens were processed with the freeze-fracture-freeze-drying technique and then analyzed in the so-called bulk specimen form. The studies were carried out during the years 1980-81, when intranuclear monovalent ionic composition was studied in detail. From the retained total elemental peak list, it was possible to calculate retrospectively the relative intranuclear Mg and P contents. The data processed by nested (hierarchical) analysis of variance show that the intranuclear Mg content of the 5 diagnostic groups (normal thyroid tissue, thyroiditis, benign adenomas, differentiated carcinomas and undifferentiated thyroid tumors) increases significantly, in parallel with the increasing malignancy, but the P content remains unchanged. One can conclude that the elevated intranuclear Mg content in the tumors of high malignancy may be of diagnostic importance, and a warning signal for the therapeutic approaches based on Mg-supplementations.

Data summarizing enamel prism shape, size and spacing are reported for the molar enamel of 55 species of small eutherian mammals including primates, bats, tree shrews, flying lemurs, insectivorans and representatives of a variety of fossil families. Confocal photomicrographs reveal that the subsurface enamel of most species is characterized by arc-shaped prisms. The lack of a clear distinction between pattern 2 and pattern 3 prism configurations within single specimens suggests that the broad category "arc-shaped prisms" is the most appropriate descriptive grouping for these species. Of the total sample, three species exhibit only circular prisms while no evidence of prismatic enamel was found in two bats. Prism shape is not an informative phylogenetic character at the ordinal level for these morphologically primitive and relatively thin-enameled taxa. Significant differences between species in several prism size and spacing variables (central distance between prisms, prism diameter, prism area and the ratio of prism area to estimated ameloblast area) suggest the potential for further analyses of quantitative variation to document evolutionary relationships within or among family-level groups.

The development of nerve fiber arrangements of the organ of Corti was studied in rabbits 1, 3, 5, 7 and 12-days-old using thick sections from celloidin-embedded cochleas which were examined under a scanning electron microscope. The arrangements of nerve fibers varied with developmental age. The tunnel spiral bundle was thick and loosely collected in the immature cochlea. The outer spiral fibers were recognized even in the narrow space of Nuel in the one-day-old cochlea. As Nuel's space is extending, the fibers course along the medial side of Deiters' cells. The arrangement of the outer spiral fibers was irregular and sparse in the five-day-old cochlea, in contrast to the regular parallel pattern of the adult cochlea. Adult-like parallel arrangement of the outer spiral fibers was seen in the twelve-day-old cochlea. In the three-day-old cochlea, irregularly running nerve fibers were seen along the outer spiral fibers. They may be efferent axons which develop afterwards. Club-like immature nerve endings were recognized at the base of the outer hair cells in the seven-day-old cochlea. Some fibers climbed high up along the medial wall of the outer hair cells. A nearly mature pattern was seen in the twelve-day-old cochlea. This study confirms previous reports on the development of cochlear innervation.