Scanning electron microscopy最新文献

Organic material associated with the calcium oxalate crystals in urinary stones and experimentally induced nephrolithiasis was stained with colloidal iron and analysed by energy dispersive x-ray microanalysis using standard techniques. Iron was positively identified in the stained specimens indicating that some of the organic material is an acidic mucosubstance. The results also indicate that some of the organic material of urinary stones may originate in the kidneys.

The development of the saccular otolith and the otolithic membrane was studied in the toadfish (Opsanus tau) using scanning and transmission electron microscopy. Development of the saccular otolith and its otolithic membrane in Opsanus begins with the formation of the primordia in embryos of 17-20 somite age. Calcification of the primordia begins shortly afterwards, although increased calcium layering and formation of the otolithic membrane corresponds to the development of a group of cells lying peripheral to the developing sensory epithelium. These cells contain an abundance of rough endoplasmic reticulum.

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.

Single intact frog skeletal muscle fibers quick-frozen after known time intervals following electrical stimulation are examined electron microscopically in thin sections, after freeze-substitution, in freeze-fracture/etch preparations, and in cryosections prepared for x-ray microprobe analysis. Techniques are described to perform these operations on a single fiber. Notable morphological differences between conventionally fixed and cryopreserved muscle fibers, and between fibers quick-frozen at different post-stimulation intervals are demonstrated.

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.

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.