Scanning electron microscopy最新文献

Various preparatory techniques were used to improve scanning electron microscopy images of the fine structure of vascular, cellular, and cordalreticular components of normal human spleens. The progressive method of fixation (GTGO) applied in the present study, allowed air drying of the tissues and rendered the specimens conductive even in newly fractured surfaces. Vascular perfusion proved necessary only in studies of the splenic blood vessels, while a simple immersion of tissue blocks in the washing solution resulted in better images of the white pulps. Interstitial (transsplenic) perfusion was found to be superior to vascular perfusion for routine preparation of spleen tissues, and freeze-cracking did not necessarily lead to improved images of the specimen's surfaces. Combined with proper washing and shaping protocols, the GTGO procedure is shown to be a superior mode of specimen preparation, abolishing most traditional artifacts and obtaining clear images of the complex splenic tissue.

Thin and semithin sections were extensively examined by the secondary electron (SE) detector in a conventional scanning electron microscope (SEM), and in a transmission electron microscope with a scanning attachment (STEM). Various parameters, in particular the beam voltage, were shown to affect the final SE image (SEI). As for SEM observation, a surface contrast was imaged at low primary electron (PE) voltages (0.6-2 kV), whereas a subsurface contrast predominated at higher energies (15-30 kV). In STEM, significant differences were not detected by varying the PE in the 20-100 kV range. Surface and subsurface information was simultaneously imaged even though the SEI were better resolved at the highest energy.

This paper reviews published materials on statoconia formation in birds, and emphasizes works dealing with the embryonic chick (Gallus domesticus) saccule and utricule. Histological, biochemical and histochemical aspects of forming statoconial membranes and statoconial crystals of mammals are included. Results from our work with chick embryos permitted us to conclude that statoconia probably do not form by seeding of a subunit around central core. Instead, immature statoconia may emerge already formed, from a segmenting mass of organic material that seems to be secreted by the supporting cells of the saccular and utricular maculae. Crystallization of each statoconium may involve seeding of multiple subunits around many nucleation centers in the organic matrix. Following these processes, calcium (sometimes granular) attaches to immature statoconia and become subsequently incorporated between the fibrils of the organic matrix starting at the peripheral zone and advancing toward the central core. Our transmission electron microscopy findings, histochemistry and X-ray microanalysis complements of other investigators, who used chicks with light microscopic studies. These results agree with the notion that the secretion of an organic matrix constitutes the first step toward the formation of the statoconial membrane and statoconia. We show ultrastructurally how statoconia may be assembled from the organic matrix before they acquire their characteristic geometric shapes.

The present paper describes the use of a quantitative renal vascular casting method to study the changes associated with kidney disease. Several animal models of hypertension (spontaneously hypertensive rat, SHR, with its normotensive rat the Wistar Kyoto, WKY; Dahl salt sensitive DS - hypertensive, and salt resistant DR - normotensive) were examined at time points when the systemic blood pressure was rising (6 and 12 weeks of age) and following renal denervation (in SHR-WKY rats). The SHR appears to have a smaller caliber afferent arteriole at both 6 and 12 weeks of age. This difference is probably not entirely due to sympathetic vasoconstriction since the strain related afferent arteriolar diameter difference was still present after renal denervation. In the Dahl rats, there is not much of an intrarenal vascular difference between the DS and DR rats with the only real finding of a smaller distal afferent arteriolar diameter found in outer cortical nephrons of the DR. The two models of acute renal failure (ARF) that were studied include, the glycerol model (known to initially cause an intense vasoconstriction) and gentamicin, a nephrotoxic antibiotic. Two time points were examined for each of these models. As expected in the glycerol model there was an intense vasoconstriction at three hours which essentially was gone at 3 days - a time when the renal failure was fulminant. The glomerulus appeared to be contracted at three hours as well. In the gentamicin model no renal vascular alteration was seen at 6 days, when renal failure was mild while at 10 days, when renal failure was pronounced, outer cortical afferent arterioles appeared to be moderately constricted. In the 5/6 nephrectomy model of chronic renal failure, the glomeruli were smaller in rats in renal failure than in the controls.

Preparative methods for scanning electron microscopy of chromosomes are dependent on the original source of material. Chromosomes extracted from unfixed metaphase cells via isolation buffers tend to show topography and surface morphology which may have been induced by the choice of isolation buffer itself. Furthermore, this type of preparation often precludes any chromosome identification, as many metaphases have been pooled, and also the chromosomes from these preparations are not suitable for the banding techniques regularly used in clinical cytogenetics. Our own approach has been to use the standard cytogenetic approach, starting with methanol-acetic acid fixed, air dried metaphase spreads, allowing both identification of individual chromosomes, and also the facility for various banding procedures such as G and C banding to be performed. Chromosomes are subsequently "reprepared" for SEM, using rehydration, glutaraldehyde fixation, and osmium impregnation using Thiocarbohydrazide (TCH). This method produces chromosomes which can be examined at high resolution, without metallic coating, for their topography, surface morphology and chromatin organisation, and the changes produced by banding techniques which give rise to a structural alterations resulting in differential staining in the light microscope.

Hydromer-coated polyurethane (Erythroflex) catheters, unused, or intravenously inserted for 2-20 days, were studied by scanning electron microscopy (SEM). Both unfixed and fixed (2% glutaraldehyde in phosphate buffer), and air-or critical-point dried (CPD) specimens were investigated. The catheter segments were sputter-coated with approx. 20 nm gold and studied at an accelerating voltage of 20 kV. The specimens were examined for surface depositions, thickness and structure of the Hydromer layers, and occurrence of adhering and embedded bacteria. The outer Hydromer layer showed, in the unused specimens, scratches and fissures, as well as adhering foreign bodies. In used specimens, the layer was swollen, with cracks (like "dried earth"), and, occasionally, amorphous substances and coccoid bacteria were seen adhering. Damage to the layer, or even its total disappearance was also noted in some specimens. The inner (luminal) Hydromer layer was, in unused specimens, clean and slightly wavy. In used catheters, it was thicker, possibly swollen, with small, isolated or agglomerated protrusions, like a "lunar landscape". Adhering platelets and amorphous substances were also occasionally seen. The results suggest that the Hydromer is a fragile material in both its dry and wet forms. Thus, the Hydromer-coated catheters should neither be stored in flexible packs, nor inserted by the Seldinger technique. The findings do not support the belief that the Hydromer-coating can prevent either thrombus formation, or intraluminal occlusion of the in-situ catheters.

This paper reviews previous findings and introduces new material about otolith end organs that help us to understand their functioning and development. In particular, we consider the end organs as biological accelerometers. The otoconia are dealt with as test masses whose substructure and evolutionary trend toward calcite may prove significant in understanding formation requirements. Space-flight helps illuminate the influence of gravity, while right-left asymmetry is suggested by study of certain rat strains.

The surface structures of mouse urinary bladder epithelium, the urothelium, were examined in SEM. The entire surface area of both a moderately and a well stretched bladder were studied. No regional differences were found in either case. The moderately stretched bladder showed deep folds, while the well stretched bladder had only small folds giving the bladder an accordion-like appearance. In both bladders the typical surface structures were microridges arranged in a honeycomb-like pattern. The present study indicates that focal or regional differences found in bladders treated with chemicals or exposed to radiation are a result of the treatment itself, and not of differences normally occurring in the urothelium.

Scanning electron microscopic examination of the gastric surface epithelial cells is often hindered by the presence of a coating material. Several methods for removal of coating material on feline gastric mucosa were utilized. The cleansed tissues were evaluated using the scanning electron microscope to assess damage caused by the use of various cleansing methods to surface epithelial cells. The stretched stomach washed several times, including rubbing the mucosal surface with gloved fingers, yielded the best results with no apparent damage to the surface epithelial cells. Flushing unstretched stomachs with saline only did not adequately remove coating material. Flushing unstretched stomachs with saline while stroking the surface with a cotton tipped applicator stick removed debris but damaged the surface epithelium.

Pancreatic acinar cells are thought to secrete a fluid containing digestive enzymes and electrolytes and use e.g. calcium as a second messenger upon stimulation. Together with their pronounced morphological polarity, they provide a model system to study the effect of different preparation methods for quantitative biological electron probe X-ray microanalysis (EPXMA) of ultrathin sections. Several preparation methods i.e., freeze-drying and plastic-embedding, freeze-substitution (2 days) and freeze-drying of ultrathin cryosections have been applied to examine the retention of sodium, magnesium, phosphorus, sulfur, (chlorine), potassium and calcium in subcellular compartments (basal cytoplasm, apical cytoplasm, mitochondria and zymogen granules). In freeze-substituted samples the phosphorus, potassium and sulfur concentrations were 2-3 times lower in all compartments compared to freeze-dried, plastic-embedded samples. Intracellular potassium-to-sodium ratios obtained on frozen substituted and frozen-dried, plastic-embedded samples were considerably lower than for cryosections. Element gradients between adjacent organelles were large in frozen-dried cryosections, smaller in frozen-dried plastic- embedded samples and insignificant in frozen-substituted samples.