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The destruction of secondary mouse-embryo (ME) cells by Naegleria fowleri was studied by indirect immunofluorescence with ME-cell antiserum as a specific label to trace the fate of mammalian-cell cytoplasm. The appearance of naegleria-induced cytopathic effect in the cultures coincided with the accumulation of discrete particles containing granules of ME-cell antigen within the cytoplasm of amoebae, suggesting that the organisms ingested host-cell material. In cultures containing cytochalasin B, a non-lethal inhibitor of phagocytosis by N. fowleri trophozoites failed to acquire any granular fluorescence and were not cytopathogenic. The engulfment of mammalian-cell cytoplasm by the organisms was confirmed when thin sections of naegleria-infected ME-cell cultures were examined by electron microscopy. Amoebae were seen in the process of detaching portions of cytoplasm from whole ME cells by means of distinctive ingesting pseudopodia, and fragments of mammalian-cell cytoplasm were identified within the food vacuoles of trophozoites. There was no evidence for cytotoxic disruption of ME cells before or during engulfment of these fragments. It is concluded that N. fowleri trophozoites attack and destroy cultured ME cells by a phagocytosis-like mechanism alone, without the aid of any amoeba-associated cytotoxic or cytolytic agents. The possible significance of these findings with respect to the in-vivo pathocity of N. fowleri is discussed.
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Experimental glomerulonephritis was produced in 16 rabbits by intravenous injections of ovalbumin in high doses (0.1 g/day during the first week, 0.2 g x 6/day during the second). The animals were killed on day 14. At that time all animals had 2--4+ proteinuria and a serum C3 level reduced to about 50% of the control level; 11 animals had a significantly raised blood urea level. In all rabbits the antigen had induced severe proliferative glomerulonephritis. Electron microscopy showed that many of the cells accounting for the hypercellularity were monocytes. Surprisingly, electron dense deposits were few and small, mainly on the subendothelial and subepithelial aspects of the glomerular basement membrane. In all the animals ultrastructural immunoperoxidase technique revealed deposits containing ovalbumin, rabbit IgG and C3. With immunofluorescence sparse deposits were occasionally seen. It is concluded that a severe experimental glomerulonephritis can be produced in a state of antigen excess, with the deposition of immune complexes being minimal. Immuno-electron microscopy is essential, however, in detecting even the smallest animals of deposited immune reactants.
Two strains of Agaricus bisporus have been investigated by fluorescent microscopy and scanning electron microscopy. Somatic nuclei, stained with auramin O and examined by fluorescent microscopy, appear to be randomly distributed, divide asynchronously, and assume a nonclassical or "two-track" configuration during mitotic metaphase. A similar configuration has been observed for nuclei during meiosis, but early meiosis in A. bisporus appears to be classical, usually with nine pairs of chromosomes evident during prophase I. Scanning electron microscopy has been used to document developmental stages in the formation and germination of basidiospores. Two-spored basidia were predominant, but occasionally one- or three-spored forms were observed. Four-spored basidia were absent, and uninucleated basidiospores were exceedingly rare to absent.
Operatively removed gallstones were examined on their surfaces and in fractured cross sections by incident light microscopy and scanning electron microscopy. In addition, micro-bore samples and X-ray crystallography were done. Five gallstone types consisting of three basic structural layers are differentiable by incident light microscopy. The three layers consist of a central nucleus which is always present, a radially structured middle layer, and a fine crystalline outer shell, the presence or absence of the latter two layers differentiating the stone types. Two crystal structures could be differentiated by electron microscopy; a flat and a globular type. The nucleus is always of the globular crystalline type, while the outer layers are flat crystalline. From this we were lead to believe that the conditions in vivo, under which the different layers of a gallstone are built, change. The micro-bore samples lead us to believe that calcium is only secondarily layed down in the gallstone framework. White crystalline deposits, which were formed several seconds after fracture, were discovered on the fractured gallstone cross sections.
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Dog prostates under defined hormonal influences were investigated by light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The normal acinar cell apices exhibited well-developed, densely packed microvilli. TEM demonstrated numerous secretory granules, indicating a high secretory activity. Following castration, the acinar cells of the dog prostate showed rounded apices. Most of the microvilli disappeared and only knob-like protrusions were seen. Castrated dogs following administration of 3 alpha-androstandiol showed fewer microvilli than the controls; however, a well-developed undulating surface could be observed. Castrated dogs given 3 alpha-androstandiol and cyproterone acetate showed almost completely atrophic glandular cells. Prostates of dogs with spontaneous benign prostatic hyperplasia (BPH) were characterized by pleomorphism of cell shapes and surfaces. The different hormonal influences induced changes of the prostatic surface structures and secretory activity.
Scanning electron microscopy allows a tridimensional morphological study of the cellular elements of the pathological human synovial fluid. The cells are grouped into two populations: macrophage cells and round cells, whose differentiation is more difficult: polynuclears, lymphocytes and synovial cells. The combination of scanning electron microscopy and X-ray diffraction makes it possible to describe and indentify crystals of sodium urate and of triclinical, dehydrated calcium pyrophosphate.
Scanning electron microscopy of permanent tooth buds of the monkey confirmed that mineralizing interrod enamel surrounds Tomes' processes on three sides, forming pits that restrict enamel rod formation. The forming face of the enamel rod, which is the floor of the pit, angled toward the tooth surface at the apical edge of the pit, the side nearest the cervical region of the tooth. Consequently, the apical edge of each pit was the only site where both rod and interrod enamel were formed at the nascent tooth surface. The ameloblasts had two secretory surfaces. One was the microvillous surface of the short Tomes' process abutting the forming face of the enamel rod. The other surface, closer to the ameloblast, was between Tomes' processes, abutting the crests of interrod enamel which formed the pits. At each site forming enamel crystallites had specific orientations. Due to the angle of the forming face of the rod and the short Tomes' process, crystallites with both rod and interrod orientation form at the same time and the same plane within the apical (cervical) margin of each rod. It is hypothesized that indistinct boundaries between rod and interrod enamel at the apical margin of each rod are due to both secretory surfaces of ameloblasts secreting at the same time and at the same site.
Scanning electron microscopy (SEM) has become a popular means of studying micro-organisms which associate with surfaces. However, as yet no detailed examination has been made of the influence of specimen preparation on the number of organisms finally seen on the SEM screen. In this investigation critical assessment is made of the influence of a wide range or preparative factors on the preservation of filamentous bacteria associated with the epithelial surfaces of rat intestine. Organisms were quantitated using a rigorous counting method (transect line analysis); statistical testing of these counts enabled the comparison of different preparative factors. The composition of the fixative was found to significantly influence the number of organisms preserved; of the fifteen fixatives studied, Karnovsky's fixative with ruthenium red best preserved surface-associated organisms. The influence of other factors on the number and appearance of preserved organisms was also examined. These factors included the washing of specimens prior to fixation, the storage of fixed specimens, and the handling and storage of critical point dried specimens. The results are discussed with reference to the optimal methods for preparing specimens for SEM.
Scanning electron microscopy (SEM) has been used during the past few years to determine surface alterations of cells infected with a variety of RNA and DNA viruses. Infection of different cultured cells by RNA and DNA viruses usually revealed dramatic shape changes with surface alterations. The most frequent changes seen were "rounding up" of cells and the development of surface microprojections such as ruffles and microvilli. In the light of available knowledge, suggestions are made in this review for future SEM studies in this field with more sensitive methodologies, which will enable even better characterization of virus-induced cell surface changes.
Scanning electron microscopy was used to observe surface fine structure of germinal epithelium and granulosa cells of human ovaries from 24 patients with polycystic ovaries and primary infertility. Synthetic LH-RH was administered intravenously and serum LH was measured at frequent intervals before and after LH-RH injection. The PCO patients were arbitrarily classified into two groups on the basis of ovarian morphology: typical PCO (Type I) with greater LH response than the lower LH response of a typical PCO (Type II). The germinal epithelium which did not completely cover the surface of the normal ovary was characterized by patchy areas of cells with and without dense microvilli. In normal preovulatory follicles, most granulosa cells were polyhedral in shape with smooth surfaces, whereas those facing the follicular cavity were elongated and flattened and were covered with material having a filamentous/reticular texture. In PCO the germinal epithelium surrounding the whole surface possessed dense microvilli, solitary cilia, and blebs, resembling the fetal ovary. In normal ovaries, the follicular cells were uniform in size and shape with microvilli and evaginations. The PCO cells have irregular size and shape with few microvilli.