Scanning microscopy最新文献

Fractal dimension has been used extensively as a descriptor of the rugged outlines of fine-particles. Potentially, it may be a useful parameter for characterizing the outlines of fine-particles which have been subjected to some form of chemical degradation. Here, fractal dimension values have been computed for the outlines of microscopic lead fine-particles both before and after weak hydrochloric acid dissolution experiments. Values obtained for the post-dissolution rugged profiles were greater than those of the pristine fracture grains which had a Euclidean form. The profiles of the degraded fine-particles could be characterized by a single fractal dimension value, or they exhibited multifractal behavior. Data from profiles of fine-particles lead from the natural environment of the soil suggest that fractal dimension calculations may provide a useful descriptor for particles which have undergone chemical dissolution and transformation in such an environment.

The concentrations of Na, Mg, P, S, Cl, K and Fe were determined by microprobe in near 100% hematocrit suspensions of rabbit and dog erythrocytes prepared by freezing and drying. These cells are representative, respectively, of "high" potassium, "low" sodium, and "high" sodium, "low" potassium cells. Water contents of the cells were the same, as were, approximately, the levels of Cl, S and Fe. Rabbit P was nearly double that of the dog. For the rabbit, the cell Na/K ratio was 0.21 and for the dog 15.4, illustrating the major diffusible electrolyte difference between these two types of cell. The rabbit erythrocytes showed an apparent negative immobile charge density of 95 meq/kg of cell water and the dog 56 meq/kg cell water, a distinct difference. Serum electrolytes in the two species are exactly comparable (Standard Tables). Ionic distribution in these cell types was treated by the Gibbs-Duhem equation representing two heterogeneous systems in thermodynamic equilibrium with the blood serum. Factors to be considered are: (1) the composition of the erythrocyte and its net immobile charge; (2) the physicochemical properties of the individual ions (charge, ionic radius, hydration energy, standard chemical potential); (3) the dielectric constant of the dispersion medium (in this case, water); and (4) the binding constants of the ions. The hypothesis of "active transport" (the sodium-potassium pump) is specifically rejected as an explanation of ionic differences.

The effect of macromolecules on the crystallization in solutions with an ion-composition and a pH corresponding to that of urine in the distal part of the distal tubuli was examined by recording the number and volume of crystals in a Coulter Multisizer and by studying the crystal morphology with scanning electron microscopy at different degrees of evaporation. The experiments were carried out with 100 ml samples of salt solutions with and without different concentrations of dialysed urine (dU) from normal subjects. Addition of dU resulted in a greater number of crystals and a reduction in the mean crystal volume (MCV). Under the experimental conditions, the maximal effect of the macromolecules appeared to be accomplished in solutions with an initial dU concentration of 10%. The precipitate was strongly suggestive of calcium phosphate (CaP) as shown by scanning electron microscopy and Raman spectroscopy. This conclusion was further supported by the ion-activity products of calcium oxalate (CaOx) and different CaP salts in those samples in which crystal formation was recorded. The obtained results give support to the view that macromolecules might exert a promotive effect on the nucleation of CaP. The macromolecules also appear to counteract the development of large CaP crystals, but whether this is due to an inhibition of crystal growth, an inhibition of crystal aggregation or both could not be concluded from these experiments. The way in which CaP crystals initially form in the nephron might be of importance for the subsequent crystallization of CaOx and the formation of CaOx containing stones.

Unique spiral structures, located in the wall of the hepatic venous system in the dog, were examined in the central veins and the hepatic venous branches, utilizing microvascular corrosion casting and freeze-fracture technique in scanning electron microscopy and transmission electron microscopy of tissue sections. The whole hepatic venous system was divided into 4 portions: the central, sublobular, collecting and branches of the hepatic veins. The central vein was spindle-shaped with several compressions. Removing the endothelial cells of the central vein, pathways of venous sinusoids were like a labyrinth. In the sublobular veins, spiral structures distinctly appeared as the diameter increased. Beneath the endothelial cells in the constricted portions, smooth muscle bundles were found. The spiral structures gradually became irregular in the collecting veins and discontinuous to form shallow constrictions in cast thicker branches of the intrahepatic veins. A single, fine spindle of the central vein was formed by the arrangement of liver cells. The spiral structures of the sublobular vein were formed by smooth muscle bundles. Irregularity of the spiral structures in the collecting veins was caused by smooth muscle bundles anastomosing with adjacent ones. Disappearance of the spiral structure in cast thicker branches of the intrahepatic veins was due to absence of muscle bundles.

This study describes the morphology of the accessory sex glands of the adult male rat as observed by scanning electron microscopy (SEM). The purpose was to obtain a systematic and comparative SEM description of these glands and to evaluate different preparation techniques. A common morphological feature is polyhedral delineation of the cells, which exhibited a variable convexity of their apical surface. The cell apices were more or less studded with microvilli. Nevertheless, it was possible to distinguish the glands by their surface morphology. In the ventral prostate, there was a considerable heterogeneity in cell surface appearance. The lateral lobe had a characteristic brush border, and in the dorsal lobe, surface blebbing and intracellular cisternae were observed. The cells of the seminal vesicle were covered by long microvilli, while particularly distinct, elevated cell borders and intracellular cisternae were typical for the coagulating gland. The secretory mechanism was merocrine in the ventral and lateral prostate and the seminal vesicle, and was mainly apocrine in the dorsal prostate. Surprisingly, only merocrine secretion was obvious in the coagulating gland. The most controversial observation, which needs further investigation, was the discovery of large orifices in the apical surface of individual seminal vesicle cells. These orifices may be indicative of an additional apocrine secretion in this gland. In studying this organ system, SEM provides information that adds to previous transmission electron microscopical investigations.

Canine bronchoalveolar and vascular corrosion casts were prepared using unfixed tissue and Dow-Corning Room Temperature Vulcanizing Silastic 734. The casts were observed using stereo light microscopy and scanning electron microscopy. The casts show the relationship between the vasculature and airway and demonstrate intricate microanatomical details. Also, microvasculature filling was enhanced using unfixed tissue as compared to my previously described technique using fixed tissue. Prewashing the microvasculature with cold phosphate buffered saline appeared to facilitate microvascular filling with silicone rubber. The described method is useful for rapidly making durable models for studying the normal respiratory airway and microvasculature. It should be useful in future studies of diseased pulmonary tissue as well as other normal and diseased tissues where microanatomical relationships between microvasculature and adjacent luminal structures are relevant.

The subject of this study was whether the ultrastructural changes in cheek epithelium of zinc-deficient rats are time related. Weanling male Sprague Dawley rats were fed a zinc-deficient diet containing 0.4 ppm zinc (ZD) ad libitum and controls were pair-fed zinc adequate diet containing 40 ppm zinc. After 9, 18, and 27 days of zinc deficiency, specimens from cheek epithelium of both groups were processed for transmission electron microscopy. Partial conversion of the orthokeratinized cheek epithelium to parakeratinized was seen as early 9 days. An electron-lucent band surrounding the nucleus was observed in ZD cells. Mitochondria, tonofilaments, keratohyalin granules and ribosomes seemed to be increased with the increase in time of zinc deficiency. There was a thickening of the stratum corneum as well as hyperplasia and widening of the intercellular spaces of the spinous layer cells. Retention of a few membrane coating granules (MCGs) in the parakeratinized layer was seen after 9 days. Parakeratinization was further increased after 18 days of zinc deficiency, and the number of MCG profiles also increased. The epithelium was fully parakeratinized following 27 days of zinc deficiency, and the number of MCG profiles was increased. It was concluded that zinc deficiency affected cell proliferation and differentiation of the epithelium as early as 9 days, and caused a delay in loss of nuclei and MCGs in parakeratinized cells.

A combined perfusion- and immersion prefixation with glutaraldehyde followed by a tannic acid/arginine/osmium tetroxide (TAO) treatment of the guinea pig cochlea is described for field-emission gun scanning electron microscopy (FEG-SEM) observation of the fine structure of the stereocilia of the organ of Corti. Conventional osmium tetroxide postfixation methods in combination with a thin conductive coating failed to show the fine structure of the glycocalyx of the epithelial lining in the endolymphatic compartment of the cochlea, in particular, on the stereocilia surface. The antennulae-like glycocalyx covering of the stereocilia surface of the more pronounced rows of outer hair cells has been demonstrated only in ultrathin sections by means of cationic markers. The side- and tip-links connecting the stereocilia have been demonstrated both in scanning and transmission electron microscopy, although at that time these structures often were considered as artificial. However, they can be visualized with FEG-SEM at low accelerating voltage (2-3 kV), and at appropriate working distance and probe current, in combination with a glutaraldehyde perfusion/immersion prefixation and TAO postfixation. Stereo images enhance considerably the three-dimensional appreciation of the stereocilia with glycocalyx lining and side- and tip-links, proving that these connections are a structural part of the hair cell.

The discovery of an organic component in kidney stones dates back to 1684. More than 150 years elapsed before the incrustation of this organic component, which is now called the matrix, was proposed as the mechanism of stone formation. The composition of the matrix remained largely unknown until the development of electron microscopy and the advances in biochemistry combined in the 1950's to usher in the modern era of renal stone matrix investigation. Composed mainly of selectively incorporated proteins generally characterized by high glutamic and aspartic acid content and the frequent occurrence of gamma-carboxyglutamic acid, the matrix displays a variable and complex composition and shares a few proteins in many stones. The embryonic stone may first appear in the renal tubules where it can acquire the blood and cell membrane proteins recently found by analysis of stone protein extracts. The combination of supersaturation, an appropriate environment, the availability of calcium binding proteins which may be abnormal, and the incorporation of proteins extracted from leukocytes and cell wall membranes may induce stone formation.

Lectin reactivity in epithelial apical cell coats of normal rat kidneys was compared to that from animals subjected to crystal inducing diets (CID). The aim was to see whether the absence of lectin reactivity in cell coats is related to intratubular calcium oxalate crystal retention. In normal rat kidneys, after a pre-embedding procedure, it was observed that at the ultrastructural level, reactivity was present but that the lectin specificity for the various parts of the nephron might have to be reconsidered. There was heterogeneity between the epithelial cells with respect to the presence of coat material in the tubular cell apices. Tubular epithelial cell apices from CID rats showed no obvious changes in lectin reactivity pattern. Lectin reactivity was present at the periphery of intratubular crystals but undetectable at true crystal attachment sites or reduced at cell apices in the vicinity of recently attached crystals or agglomerates. After a post-embedding reaction procedure, wheat-germ agglutinin (WGA)-lectin reactivity confirmed the presence of coat material in the cleft between cell apex and retained crystal at crystal-attachment sites. The WGA/Au-10 nm reaction products were also seen inside epithelial cells. WGA/Au-10 nm reaction products mark a crystal matrix component inside intratubular and retained crystals. A similar matrix was also marked by an alpha-osteopontin (alpha OPN/Au-10 nm) reaction product.