It is shown that with the aid of a schlieren optical mode described in this paper in real electron microscopes, the amplitude contrast of weak objects can be enhanced up to two-fold in comparison with the bright-field mode, if a part of the unscattered beam strikes the objective aperture. This remains true also in the case of thicker objects imaged (for example, unstained sections of biological matter). Futhermore, evidence is given for the existence of an optimum schlieren image in the transition range between strict schlieren optics and conventional bright-field microscopy. Such images are characterized by high amplitude contrast without significant distortion. Theory and experiment are shown to be in good agreement. As an application, unstained nucleosomes have been investigated schlieren-optically. Model calculations show that the ‘hole’ in their centre, which has been demonstrated from dark field images, is probably not due to a structural void (cavity), but is a consequence of the lower density of the protein core as compared with DNA.
This paper is a continuation of a series of reports on the design and construction of an atmospheric or environmental SEM. The work described is an extended study of the gas jet developed above the pressure limiting aperture (Bell, 1974; Lacaze et al., 1977). Experiments specifically aimed to establish how the vacuum in the electron optics system was affected by the relative positioning of the objective and pressure limited aperture, as well as the pumping speeds employed, specimen chamber pressure, geometry and size of apertures, and by other means. Further, the nfluence of the jet deflectors, to control the effects of this jet on the microscope system were studied quantitatively using a specifically designed apparatus. In addition, the study of the pressure gradients below the pressure limiting aperture revealed that specimens can be placed as close as radius from the aperture and still experience an almost saturated vapour pressure environment. The results of the present study are currently being used in the design of an optimum detection configuration. A preliminary result has allowed the use of 140 μm pressure limiting aperture to observe specimens at atmospheric pressures as well as the use of low accelerating voltages (e.g. 7 kV) at TV scanning rates to record on video cassette dynamic phenomena, including wetting or recrystallizing salt solutions, etc.
The smooth, proximal portion of the yolk sac placenta of the sandbar shark, Carcharhinus plumbeus is comprised of: (1) An outermost epithelial ectoderm; (2) an intervening collagenous stroma; and (3) an inner mesothelium. The surface epithelium may be one to three cell layers thick. The surface epithelium comprises two cell types. A cuboidal cell that has a dome-like apical surface covered with microvilli and an ovoid nucleus predominate. These cells contain lipid inclusions, many cytoplasmic filaments, and are joined by desmosomes. The second cell type has a convoluted nucleus and a flattened cell apex with microvilli, cilia, and paddle cilia. Golgi complexes and elements of the endoplasmic reticulum are relatively uncommon in the cytoplasm of both cell types. Microplicae also occur on the surfaces of some cells. The smooth, proximal portion of the placenta is sparsely vascularized. The innermost cellular elements of the surface epithelium rest on a prominent basal lamina. A collagenous zone separates the epithelial basal lamina from the basal lamina of the mesothelium. The mesothelial cells are squamous with a fusiform nucleus, many pinocytotic pits and vesicles, and a large number of cytoplasmic filaments. The endoplasmic reticulum, except for occasional patches of the rough type, and the Golgi complex are poorly developed. Ultrastructural tracer studies show that this portion of the placenta does not absorb horseradish peroxidase (HRP) and trypan blue.
The ultrastructural and three-dimensional arrangement of elastic reticulum and collagen in mouse parietal peritoneum is described for the first time. As seen by high-voltage electron microscope stereoscopy of thick sections, the EL forms a three-dimensional network without free ends. The central part of the EL fibre is not amorphous but contains irregular 500-100 nm fibrils along its length. Large bundles of banded collagen (also without free ends) course in and out of the elastic reticulum. The production of these two interlacing networks implies the presence of a histo-architectural sensing and orientation system for the projected cytoplasmic processes of stromal fibroblasts and also bidirectional chain assembly for both collagen and elastin. Bilaterial assembly patterns have been described for collagen but not for elastin.
During fixation of an allergenic pollen (Corylus avellana) the addition of cetylpridinium chloride (CPC) to the buffered glutaraldehyde led to the preservation of specific material which was lacking after fixation in glutaraldehyde alone. CPC-reactive substances form a distinct covering layer around the pollen grains, but they also occur within the baculoid region of the sexine and the spherosomes of the cytoplasm. In a non-allergenic pollen (Pinus mugo) no CPC-reactive material was found. A chemical similarity between the acid mucopolysaccharides precipitated by CPC in animal connective tissue and the material stained in pollen must be assumed. The possible importance of the visualized substances as to their role as allergens is briefly discussed.
Metallographic techniques have been developed for examination of wire wrap sections of neutron irradiated AISI 316 stainless steel from EBR-II. The special etching techniques used for metallographic examination of radiation and thermally induced precipitates, including sigma or chi phases and alpha ferrite, are documented. A description is given of the preparation of standard 3 mm dia TEM foils using a nickel plating technique to increase the effective size of the original 1.1–1.4 mm dia wires.
Stacked plates have been found just beneath the epithelium of the siphons of Donax sordidus and Solen capensis. Each stack is 4–8 μm deep and 17–25 μm wide and consists of a number of plates 0.3 μm wide. When viewed with a TEM each plate consists of an electron dense zone (0.1 μm wide), surrounded by a double membrane. It is suggested that these plates serve to reflect or scatter light and are an integral part of the dermal light sensing ability of these animals.
A procedure is described by which neuroglial cells from neonatal mouse brain are collected in vivo on polycarbonate membranes. By the use of scanning electron microscopy the aim was to study the morphology of collected cells. The surfaces of the glial cells showed many blebs and numerous filopodia. At higher magnifications the filopodial surfaces appeared to be covered with small round granules. On the astrocytes and oligodendrocytes semi-quantitative energy dispersive X-ray microanalysis was performed.
The electron image contrast of tungsten atom clusters changes remarkably depending on the spatial frequency, scattering factor phase, lens aberration and defocusing, but it is confirmed that the image appears in negative contrast and satisfies an anastigmatic condition when recorded under optimum focus.
Two morphometric methods, one using a transmission electron microscope (TEM), the other using a scanning electron microscope (SEM), were developed to quantitate the number of surface microprocesses, discs or pores over spherical cells. The number of the surface processes over EL-4 murine T-lymphoma cells cultured in vitro were measured by the two methods. The measurement using TEM yielded 511 ± 45 microprocesses per cell, whereas SEM enumerated 532 ± 25 microprocesses per cell. The method using a TEM, in effect, results in reduction of observed data, and may have an advantage over the method using a SEM when the structures of interest are numerous.
The general morphological features of the Gram-negative bacterium Pseudomonas avenae have been studied by electron microscopy. Electron micrographs from negatively stained specimens show the outermost surface layer to be composed of subunits arranged in a crystalline tetragonal array, with an average lattice spacing of 6.7 nm and unit cell of 9.7 nm when determined by image processing methods. Experiments designed to show the effects of various negative stains on the bacterial cell wall morphology suggest that the ‘convoluted’ or ‘smooth’ appearance of the wall material can be influenced by different stains when mixed with cells in liquid suspension.
Acute sleep deprivation (ASD) is often observed in shift workers and characterized by drowsiness and unrelenting exhaustion. The physiological and psychological effects of ASD include anxiety, depression, cognitive impairment, systemic inflammation, stress responses, and disruptions of gut microbiota. However, the mechanisms involved in the ASD-associated circadian dysregulations with regard to gut dysbiosis, systemic inflammation, physiological modulation, and psychiatry disorders remain unclear. The aim of this study was to investigate whether central nervous system disorders induced by ASD are related to inflammation, barrier dysfunction, and circadian dysregulation. We also assessed impacts on microbiota succession. Male C57BL/6 mice were randomly allocated to the control and sleep deprivation (SD) groups. Mice in the SD group were subjected to 72 h of paradoxical SD using the modified multiple-platform method for ASD induction (72 h rapid eye movement-SD). The effects of ASD on dietary consumption, behaviors, cytokines, microbiota, and functional genes were determined. The appetite of the SD group was significantly higher than that of the control group, but the body weight was significantly lower than that of the control group. The anxiety-like behaviors were found in the SD group. Alpha and beta diversity of microbiota showed significant decrease after ASD induction; the relative abundance of Candidatus_Arthromitus and Enterobacter was increased, whereas that abundance of Lactobacillus, Muribaculum, Monoglobus, Parasutterella, and others was decreased in the SD group. These effects were accompanied by reduction in fecal propionic acid. In the proximal colon, the SD group exhibited significantly higher inflammation (tumor necrosis factor-α [TNF-α]) and dysregulation of the circadian rhythms (brain and muscle ARNT-like 1 [BMAL1] and cryptochrome circadian regulator 1 [CRY1]) and tight junction genes (occludin [OCLN]) than the control group. Gut barrier dysfunction slightly increased the plasma concentration of lipopolysaccharide and significantly elevated TNF-α. Inflammatory signals might be transduced through the brain via TNF receptor superfamily member 1 A (TNFRSF1A), which significantly increased the levels of microglia activation marker (ionized calcium-binding adapter molecule 1 [IBA1]) and chemokine (intercellular adhesion molecule 1 [ICAM1]) in the cerebral cortex. The serotonin receptor (5-hydroxytryptamine 1A receptor [5-HT1AR]) was significantly downregulated in the hippocampus. In summary, 72 h of rapid eye movement-SD induced physiological and psychological stress, which led to disruption of the circadian rhythms and gut microbiota dysbiosis; these effects were related to decrement of short chain fatty acids, gut inflammation, and hyperpermeability. The microbiota may be utilized as preventive and therapeutic strategies for ASD from the perspectives of medicine and nutrition.
This paper describes a simple efficient device which permits the simultaneous staining and washing of a large number of electron microscope ultrathin sections.
A computer program written to separate and identify superimposed Selected Area Electron Diffaction (SAD) patterns is reported. Prior knowledge of reflection types and their spatial positions within a Wulff net is required.
