Scanning electron microscopy最新文献

The crista ampullaris of the guinea pig and the bull frog were investigated by scanning electron microscopy. The crista ampullaris were freeze fractured or sheared followed by maceration with 0.1% OsO4 solution. Following this, three-dimensional intracellular structures were observed. The mitochondria of the sensory cells varied in shape from globular to long and slender. Golgi apparatus and endoplasmic reticulum of the sensory cells were also demonstrated clearly. Nerve elements, nerve endings and synaptic structures were also observed stereoscopically.

The authors review the contribution of microcorrosion cast studies towards clarifying the structure of skeletal muscle microcirculation. Former studies performed on naturally contracted muscles show the presence of a primary and a secondary arterial network and a capillary network. At the level of the capillary network pericyte imprints are present. Muscles characterized by different types of metabolism show different features of the capillary pattern. Other authors have affirmed that the extended muscle is characterized by long and straight capillaries, while the contracted one features clusters of vessels all around a muscle fiber. The authors have made the present observations in order to determine how the capillary pattern of muscles with different metabolism is modified by extension and shortening of the muscle belly. The capillary pattern observed appears very similar to that observed in former studies. The differences between the oxidative and the glycolytic muscle are evident in every condition of the muscle belly. These data confirm the theory that there is a permanent endogenous difference in microcirculation between oxidative and glycolytic muscle, determined by muscle fiber metabolism.

This paper presents an overview of the study of the ultrastructure of biogenic inorganic solids (biominerals) using high resolution transmission electron microscopy (HRTEM). A range of biominerals have been studied including iron oxides, calcium phosphates, calcium carbonates and silica. The studies have revealed information concerning the structural complexity of these materials and have identified crystallographic order and disorder at the nanometre level. In addition, the results have aided the elucidation of the mechanisms of nucleation and growth of biogenic minerals.

53 Lewis lung carcinomas implanted subcutaneously into C57BL/6-mice were examined. The animals were killed at various stages of tumor growth (TG) and prepared for histology and for scanning electron microscopy (critical-point-dried tissue; vascular corrosion casts). Prior to casting animals were rinsed using different perfusion pressures. Casting was done by manual injection of the resin, whereby different influx-rates were applied resulting in low, medium and high pressure preparations. We discern 3 phases of tumor angiogenesis (TA) occurring during 4 stages of TG among which vasodilation establishes the first reaction of the host vascular system to a growing tumor implant. During this stage 1 of TG, tumor nidation, nearby sinusoidal dilated host capillaries form globular outgrowings (phase 1 of TA). Subsequently radially arranged sprouts, which preferentially arise from venous host vessels, grow into the centre of the implant (phase 2 of TA). Stage 2 of TG, early tumor growth, is characterized by necrosis of the central tumor tissue and the development of a central avascular cavity. Thus the tumor vascular system is organized like a hollow sphere with a central cavity and a peripheral vascular "envelope" with large vessels embracing the tumor and centrifugally growing vascular sprouts, which arise from the venous part of the vascular "envelope" and invade the surrounding host tissue (phase 3 of TA). During stage 3 of TG, late tumor growth, many vessels of the basket-like vascular "envelope" obliterate. In stage 4 of TG, prefinal phase, the peripheral vascular density decreases continuously. Thus vascular sprouting and proliferation of viable tumor cells is confined to basal regions of the tumor.

Using metallic gold in various assays for the motility of cultured tissue cells, the paper compares the movements of surface projections and the locomotion of polyoma (Py3T3) and SV40 (SV3T3) virus-transformed 3T3 cells with the behavior of the parental 3T3 cells. The movement of surface projections was assayed by the ability of filopodia, lamellipodia and blebs of freshly plated cells to remove colloidal gold particles from a particle-coated glass substrate. The ability of filopodia to probe the environment for points of anchorage was tested by observing cells plated on glass whose filopodia touched the surface of a neighboring area of evaporated gold. The locomotion of cells was assayed by particle-free tracks (phagokinetic tracks) which were left by migrating cells on a glass substrate which was previously coated with colloidal gold particles. The paper suggests that the ability of the transformed cells to sense environmental factors, and their behavioral controls are altered.

Several investigators have reported an association between the cytoskeleton and viral antigens. In our laboratory, biochemical immunofluorescence and immuno-gold electron microscopy studies were conducted on TX-100 extracted NIH/3T3 cells infected with Moloney-murine leukemia virus. Cytochalasin B treatment causes reversible microfilament disruption and a concomitant decrease in virus production. No effect on microtubules was seen. Immunogold electron microscopy reveals an association between cytoskeletal actin and the viral antigens gp70 and p15E. The results of these immunocytological and biochemical studies indicate that the cytoskeleton may play an integral role in transport and processing of viral gene-envelope products.

Maintenance of tear film in normal conditions is dependent on mucus layer integrity and the presence and distribution of conjunctival epithelial cell microvilli. In the present work a new methodology has been developed to gain correlative information about microprojection assessment and mucus composition, from the same specimen, by Light Microscopy (LM), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). We have characterized the glycosidic residues secreted by goblet cells in normal human conjunctiva, by means of four lectins (WGA, ConA, PNA and SBA), conjugated with FITC for LM and with colloidal gold for TEM and SEM. The cytochemical reactions were performed on histological sections of paraffin-embedded material and on semithin and ultrathin sections of both Epon embedded material directly processed for TEM and of blocks recovered from SEM and reprocessed for TEM. WGA, ConA, PNA and SBA receptors were found to be constituents of the mucus produced by goblet cells in human conjunctiva. The granules of the so-called "second mucus system" (SMS) cells were labelled mainly by WGA. A difference in the quality of glycoconjugates between goblet cells and SMS cells has been also demonstrated. Our results provide an improved method to evaluate alterations of tear film that occur in many conjunctival diseases.

Microvascular architecture of the normal human heart and myocardial focal necrosis were studied by scanning electron microscopy of corrosion casts. Casts macroscopically identical in form to the left ventricular posterior wall were prepared. The following results were obtained in the normal human heart. Most of the arterioles communicated with capillary plexuses smoothly and straightforwardly in the left ventricular posterior free wall. Arterioles which branched from the arteries ran in various directions and continued into capillaries either at right angles or obliquely in the trabeculae carneae. Capillaries running parallel with the cardiac muscle fibers ran in different directions to cross over with each other in different layers of myocardium. Capillaries in the myocardium formed a continuous and coarse net-like architecture with many bifurcations and anastomoses. Capillaries were about 5-7 micron in diameter. Some veins gathering capillaries in the epicardium ran into the myocardium and the others ran in the epicardium. Veins connecting with capillaries in the myocardium ran in the myocardial layer and communicated with larger veins. An arterio-venous anastomosis and two different types of venous-venous anastomoses were observed in the left ventricular posterior wall. At the site of focal necrosis, cross sections of dilated vessels were observed in large numbers by light microscopy and scanning electron microscopy. At the site of focal necrosis, dilated capillaries running with tortuosity were seen in large numbers by scanning electron microscopy of corrosion casts. When compared with vessels in the normal myocardium, small arterial branches were dilated and run tortuously. These dilated capillary plexuses were observed in the area which communicated with twigs branching off at the right angle from the arterial branch.

Rabbits were exposed to low levels of metal dust or metal ions by inhalation for 1-8 months, 5 days/week and 6 h/day. Following exposure lung tissue was examined by light and electron microscopy, the lung content of phospholipid was analyzed and the morphology and function of alveolar macrophages were investigated. Metallic nickel dust as well as soluble nickel chloride produced accumulation of macrophages and laminated structures in alveoli and increased volume density of alveolar type II cells. The amount of phospholipids was elevated, mainly due to an increase in disaturated phosphatidylcholine. After one month exposure to metallic nickel dust or soluble nickel chloride, the alveolar macrophages contained surfactant inclusions and were functionally activated. After 3 and 6 months exposure to metallic nickel the macrophages were 'overfed' and inactive. A similar reaction is seen in the human disease pulmonary alveolar proteinosis. Exposure to cadmium chloride gave a similar reaction pattern as nickel did but in addition interstitial alveolitis. One month exposure to cobalt chloride affected the growth pattern of type II cells which formed nodules projecting into the alveolar lumen. Four months exposure to cobalt chloride resulted in further developed type II cell nodules, areas of hyperreactive type II cells, and interstitial inflammation. Copper chloride produced no effects apart from a slight increase in volume density of type II cells. Hexa- and trivalent chromium mainly affected the alveolar macrophages which showed enlarged lysosomes. Thus, different metal ions, in similar concentrations produced different pathological effects in the lung.

The lung appears to be the major dose-limiting organ in radiation of the thorax. Early responses (less than 1 week) involve the type II pneumocyte and increased surfactant biosynthesis and secretion. Later changes, which appear to be related to the surfactant response, lead to classical radiation pneumonitis, which is often fatal. Animals which survive radiation pneumonitis develop progressive fibrosis, a late-appearing response, which reduces compliance and available air space, and is usually fatal. This study centers on the fine structural changes in the lungs of LAF1 mice, 63 weeks following various radiation exposures (5-13 Gy). Doses which are subthreshold in evoking surfactant and pneumonitic responses precipitate fibrosis and atelectasis by 63 weeks, and involve type II pneumocyte sloughing and degeneration. Of the two major deterrents to lung irradiation (pneumonitis and fibrosis), these results suggest that fibrosis always follows pneumonitis, but pneumonitis is not a necessary preliminary step to fibrosis. Bleomycin elicits several morphological alterations characteristic of radiation, and, when combined with the latter, appears to exacerbate radiation effects.