Scanning electron microscopy最新文献

Past scanning electron microscopy (SEM) reports demonstrated cell surface undulations, ridges, folds, and ruffles to support the monocytic/histiocytic nature of hairy-cell leukemia (HCL) cells. On the other hand, SEM studies illustrating spikes, villi, and microvilli on the cell surfaces favored the lymphocytic nature of hairy cells (HCs). The evidence for the 'hybrid' nature of the HCs has emerged from the demonstration of concurrent display of monocytic (ruffles) and lymphocytic (microvilli) surface features on each cell. Utilizing improved methods of sampling, fixation, and drying, the current status is that all HCs display microvilli and ruffles simultaneously. However, two distinct morphological types of HCs are acknowledged: cells showing ruffled areas next to clumps of microvilli (type A), and cells displaying microvilli interspersed among ruffles (type B). Each of the HCL cases reported in our studies had cells with either type A or type B surface features. Amazingly, these unique SEM features correlate well with the prevalent trend to classify HCs as malignant (villous) B-lymphocytes imitating (ruffled) monocytes in some functional respects.

Densely ionizing, particulate radiations in outer space are likely to cause to mammalian tissues biological damage that is particularly amenable to examination by the techniques of electron microscopy. This situation arises primarily from the fact that once the density of ionization along the particle track exceeds a certain value, small discrete lesions involving many adjacent cells may be caused in organized tissues. Tissue damage produced by ionization densities below the critical value also afford opportunities for electron microscopic evaluation, as is shown by the damage produced in optic and proximate tissues of the New Zealand white rabbit in terrestrial experiments. Late radiation sequelae in nondividing, or terminally differentiating, tissues, and in stem cell populations, are of special importance in these regards. It is probable that evaluations of the hazards posed to astronauts by galactic particulate radiations during prolonged missions in outer space will not be complete without adequate electron microscopic evaluation of the damage those radiations cause to organized tissues.

Scanning electron microscope (SEM) morphological analysis combined with energy dispersive characteristic x-ray analysis provides insight into the mechanism of biological mineralization. A time series of tissue micrographs and mineralization measurements can permit the determination of the mineralization kinetic behavior and is the basis upon which a computer model has been devised. The computer model is constructed from fundamental principles of crystal nucleation and precipitation theory. Various general forms of the model are tested against the laboratory data for goodness-of-fit using the least squares method, and two models are found to be acceptable. Both of the acceptable models involve inhibition of the mineralization process which has a reaction order ranging from one to two. A third model involving constant nucleation rate must be rejected. Having established working first principle models for the mineralization process, one can compute a constant number of nucleation sites and a supersaturation value for calcium in various mineralized tissues such as the spongiosa and fibrosa of heart valve leaflet implants. These quantities are determined and used in discussing a general theory for biomineralization which emphasizes therapeutic considerations.

Four explanted porcine aortic valved conduits were examined using scanning and transmission electron microscopy. Sources of obstruction such as neointima or "peel" and calcification were observed. In one sample the neointima was found to possess an unusually large expanse of squamous cells partially lining the luminal surface. This lining much resembled a normal endothelium, which is not an expected feature of neointima. Cells, presumably of host origin, were noted upon the leaflet surfaces. They did not seem as well organized as those found on the neointima. Calcification did not seem greatly advanced but was clearly apparent. Certain treatments proposed by others to curtail calcification are discussed and amended herein. SEM examination of three of these conduits provided good evidence of lining cells on only the inflow surface of the leaflet. The fourth conduit, however, showed cells on both inflow and outflow surfaces. These cells possessed certain characteristics of cells from leaflets of the other three conduits, but questions remain as to the precise identification of all of these lining cells. TEM examination provided cytological evidence of macrophage-like cells lining the inflow surface of a leaflet.

This report describes the effects of endotoxin treatment on the intrasplenic microcirculation and cellularity in rats. Four and 16 h after a single intravenous injection of endotoxin (2 mg/100g body weight), altered intrasplenic microcirculation was observed. The open circulation was reduced from 97% in the control rats to 79% in the endotoxin treated rats, while the closed circulation increased from 3% in the controls to 21% in the endotoxin treated rats. Such changes in the splenic microcirculation may be partly due to the presence of fibrin and the pooling of polymorphonuclear leukocytes and red blood cells in the red pulp. The most apparent cellular changes seen in the white pulp of endotoxin treated rats 16 h after endotoxin injection are the disappearance of lymphocytes from the periarterial lymphatic sheath and the appearance of many giant macrophages within the white pulp. The giant macrophages contain lymphocytes undergoing various stages of degradation. This suggests that the lymphocytes may be injured by endotoxin treatment and are subsequently phagocytosed by macrophages.

Platelet agonists and subendothelial extracellular matrix (ECM) induce morphological and biochemical changes in animal megakaryocytes, reminiscent of the response of platelets to the same substances. We have examined the behavior of human megakaryocytes exposed for up to 36 hours to the ECM produced by cultured bovine corneal endothelial cells. By phase contrast and scanning electron microscopy these megakaryocytes demonstrated non-reversible adherence and flattening with formation of long filopodia, thus confirming that human megakaryocytes acquire platelet functional capacities. In addition, megakaryocyte fragmentation into prospective platelets was apparently induced by the ECM. Up to 50% of the adherent megakaryocytes underwent spontaneous fragmentation into small particles which individually reacted like platelets on the ECM. The interaction of the megakaryocytes with the ECM was specific since no adherence, flattening or fragmentation occurred upon incubation of the megakaryocytes on regular tissue culture plastic or glutaraldehyde fixed ECM. Thus we have demonstrated platelet like behaviour of human megakaryocytes in response to this physiological basement membrane and a possible role of the subendothelium in platelet production which may occur in vivo as megakaryocytes cross the sinusoid walls and enter the blood stream.

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.

Little is known about in utero urinary bladder embryogenesis and the development of the urothelium of laboratory animals. Previous scanning and transmission electron microscopy studies in rats and mice have indicated that the highly specialized superficial cells of the urothelium complete their differentiation at a very late stage of fetal development or shortly after birth. Limitations in methodology in the past have precluded extensive examination of earlier stages of bladder development. Innovations in preparatory procedures of the bladder of rat fetuses have been developed which make possible detailed scanning and transmission electron microscopic and light microscopic examination of cloaca and urinary bladder as early as day 11 of gestation.

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.

Published studies indicate that genes and dietary manganese deficiency cause vestibular defects and ataxic behaviors. Manganese deficiency during development causes otoconial defects in mice, rats, guinea pigs, and chicks. Mutant genes cause otoconial defects in mice, mink, and poultry. Manganese supplementation prevents the otoconial defects in some mutant mice and mink. Manganese is essential, before crystallization of the otoconia, for synthesis of mucopolysaccharides and otoconial matrix. Such defects can be induced, after otoconia are crystallized during fetal development, by dietary zinc deficiency and sulfonamide treatment (inhibits carbonic anhydrase, a zinc-requiring enzyme). Manganese and/or zinc supplementation ameliorates otoconial defects in pallid and lethal-milk (zinc-deficient) mice. Studies herein show that: Developing otoconia can be quantitatively labeled with 45 Ca. This may provide a means for studying calcium metabolism in otoconia over a prolonged period of time and for determining the possible effects of diet, drugs, and other factors on otoconia. Otoconial defects, induced after otoconia form in the fetus, were observed in newborn mice, but disappeared by two days after birth. Conditions of the inner ear may contribute to the calcification of otoconia. Manganese and zinc supplementation of pallid mice via acidified drinking water is more effective than dietary supplementation in preventing otoconial defects. The effectiveness of zinc but not of manganese is related to maternal genotype (+/pa vs. pa/pa). The effect of supplementation of the dams with zinc but not with manganese increases over successive litters. These studies indicate the potential for interaction of genes and trace minerals on otoconial formation and maintenance.