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Scanning Electron Microscopic (SEM) observations were made on the adult worms of Brugia malayi from rodent hosts. Descriptions of the surface features of mouth, vulva, anus, caudal papillae and spicules are given.
Histological characteristics, as observed by scanning electron microscope, of the secondary roots of Harpagophytum procumbens DC. (Pedaliaceae), a drug widely used in South African traditional medicine, specially by Bushmen, Hottentots and Bantu, are described in detail. It has been possible to reveal some morphological elements that, together with superficial granular material containing harpagoside and harpagide, allow drug identification.
A scanning electron microscope (SEM) study of corrosion cast preparations of the vessels of the spiral lamina and the spiral limbus was carried out in adult rats. This method confirms present knowledge of the modiolar vascularization and also shows its distribution in a three-dimensional model. As a result of this technique we have been able to demonstrate the modiolar vascular supply of the organ of Corti at different levels.
The scanning electron microscope was used to examine resected areas of eight roots of human teeth extracted after long intervals following surgical procedures. Some resorption lacunae were observed in the areas with protuberances of newly formed cementum. In the lacunae, honeycomb-like structures were found. On the resected surface, residues of ligaments and periodontal fibers, and in one of the specimens dentinal tubules with odontoblastic processes protruding above the surface were present.
Most of the work carried out in relation to contrast mechanisms and signal formation in an environmental scanning electron microscope has yet to consider the time dependent aspects of image generation at a quantitative level. This paper quantitatively describes gaseous electron-ion recombination (also known as 'signal scavenging') in an environmental scanning electron microscope at a transient level by utilizing the dark shadows/streaks seen in gaseous secondary electron detector images of alumina (Al2O3) immediately after a region of enhanced secondary electron emission is encountered by a scanning electron beam. The investigation firstly derives a theoretical model of gaseous electron-ion recombination that takes into consideration transients caused by the time constant of the gaseous secondary electron detector electronics and external circuitry used to generate images. Experimental data of pixel intensity versus time of the streaks are then simulated using the model enabling the relative magnitudes of (i) ionization and recombination rates, (ii) recombination coefficients and (iii) electron drift velocities, as well as absolute values of the total time constant of the gaseous secondary electron detection system and external circuitry, to be determined as a function of microscope operating parameters such as gaseous secondary electron detector bias, sample-electrode separation, imaging gas pressure, and scan speed. The results revealed, for the first time, the exact dependence that the effects of secondary electron-ion recombination on signal formation has on reduced electric field and time in an environmental scanning electron microscope. Furthermore, the model implicitly demonstrated that signal loss as a consequence of field retardation due to ion space charges, although obviously present, is not the foremost phenomenon causing streaking in images, as previously thought.
The scanning electron microscope (SEM) was used to evaluate the cutting edges of curettes as they came from the manufacturer, after they had been made dull and after they were resharpened by several standard resharpening techniques and one experimental technique. Micrographs were taken of the cutting edges with the SEM at a standard magnification. The quality of the cutting edges was blindly evaluated by five independent examiners who unanimously agreed that the experimental resharpening technique produced the highest quality edge. The experimental resharpening technique used a Whittler Instrument Sharpener on the face of the blade followed by a rotating, abrasive impregnated, felt wheel on the lateral surface of the blade.
The authors observed, with a scanning electron microscope, the dermal surfaces of experimental wounds, following the enzymatic digestion with trypsin of the dermo-epidermal junction. Cut lesions showed an early reconstitution of the basement membrane and progressive convergence of the margins. A peculiar arrangement of the dermal crests was also observed. In wounds with loss of substance, the complete coating by newly formed basement membrane took longer. There was an early deformation of the holes of hair follicles in the undamaged dermis surrounding the lesion, as well as the appearance of creases that moved toward the center. This process was over within a few days; then the lesion became very small and the holes of the hair follicles reappeared. The results suggest a force of traction bound toward the center of the lesion and acting on the surface, the effects of which on the basement membrane are most evident between the eighth and the 15th days.
Scanning electron microscopic studies were made on the mucosa of newborn middle ear. The results were: 1. The epithelial surface was found to contain four types of cell: the ciliated cell, the nonciliated cell without secretory granules (SG), the nonciliated cell with secretory granules (SG) and the flat cell. 2. The ciliated cell population appeared in the following order (from dense to sparse): eustachian tube, hypotympanum, antetympanum, epitympanum, promontory and post-tympanum. 3. The density of nonciliated cell without SG population was gradually increasing from anterior to posterior part of middle ear. 4. The population of nonciliated cell with SG was fewer and they were always found near the ciliated cells. 5. The flat cells were only seen on the flaccid part of tympanic membrane. This paper suggests that the ciliary system is basically mature and the development of mucus secreting members still is not perfect in newborn middle ear mucosa.
Scanning electron microscopic observations were made on adult Angiostrongylus cantonensis, The apex of the head has a round mouth with two rows of 6 sensory papillae each around it. The papillae of the outer row are more rudimentary and inconspicuous. A pair of amphidial pores are visible on the external side of lateral papillae of the inner row. The surface of the body is covered with a circular striated cuticle and short longitudinal ridges lying between two circular cuticles. The two copulatory spicules at the posterior end of male worms are obviously different in morphology. According to their morphological characteristics, we named them "tube-like" copulatory spicule and "grooves-like" copulatory spicule. The former, when enclosed in the latter, appeared as a single one. The copulatory bursa of the males and the structures of the tail part of the female are also described.
The significance of the ElectroScan environmental scanning electron microscope (ESEM) as a processing tool for studying dynamic morphological changes under controlled temperature/atmosphere conditions was evaluated. The ability to observe dynamic processes in situ, which cannot be achieved by other means, is critical to understanding microstructural formation. Processing of printed copper thick films on ceramics was used as a test case, wherein morphological changes associated with the steps of organic binder removal and sintering of copper particles were observed/examined in real time. Good agreement was seen between microstructures obtained in the ESM and those achieved in a belt furnace when similar process variables were used. When processed in atmospheres which were proven to induce sintering in a conventional belt furnace, sintering was evident in both cases, and the microstructural changes were documented on video-tapes in real time. Determination of critical event temperatures was achieved--that is, binder burnout occurring between 270 degrees and 350 degrees C, onset of oxidation at 520 degrees C, and sintering starting at 770 degrees C. It was thus verified that the microstructural changes during the copper thick film sintering process can be observed in situ using an ESEM.
The aims of this experimental scanning electron microscopic study were to identify the levels at which cervical ventral nerve roots, or the rootlets by which they are attached to the spinal cord, rupture under traction and to document the resulting damage. This information would provide the basis of a rationale for repairing rootlet avulsions which may follow brachial plexus traction injuries in man and which cause severe impairment of upper limb function. Traction was applied to C4 to T1 ventral roots until rupture occurred, in 10 freshly fixed and three living anaesthetized Wistar albino rats and in one human post-mortem specimen. Rupture occurred at the rootlet-cord junction in 80% of cases. Most individual myelinated fibres broke at the central-peripheral nervous system (CNS-PNS) transitional node which, in the cervical region, lies at the bottom of an endoneurial invagination surrounding each fibre and extending deep to the cord surface. Fibre rupture at more distal levels occurred internodally, and a length of axon commonly protruded well beyond the level of sheath rupture. Some sheaths broke cleanly across but the torn surfaces of others tapered, perhaps because of rupture at Schmidt-Lanterman incisures. The cellular and connective tissue rootlet sheaths ruptured where they were continuous with the pia mater. Ruptured fixed and unfixed tissues were ultrastructurally similar. It is clear from the findings of this study that regeneration would take place entirely in a PNS environment. The endoneurial invaginations would ensure that sprouts emerging from transitional nodes would be guided distally into rootlets surgically apposed to the torn transitional zone.
There are a number of scanning electron microscopic (SEM) studies on retinal photoreceptors of vertebrates. However, most of these are concerned with the adult retina, and only a very few deal with developing photoreceptors. In man, SEM studies have not been carried out on photoreceptor morphogenesis during fetal or postnatal stages. Hence, the present study was undertaken to examine the sequential morphological changes in developing photoreceptors during different gestational ages in the human retina. Retinas of human fetuses of gestational ages of 10-25 weeks and from autopsy of a 5-month-old infant were processed for SEM. The observations show some new information on the morphogenesis of photoreceptors. At 10-11 weeks, the outer and inner neuroblastic zones are well developed and separated from each other by the layer of Chievitz. By 15-16 weeks, the photoreceptor precursors appear as spherical inner segments on the scleral surface of the outer neuroblastic zone. Cilia develop as small protrusions from the apical ends of the inner segments. Photoreceptor inner segments become arranged in mosaic pattern by 18-19 weeks. In the mosaic, large cone inner segments (putative blue cones) stand out prominently from the remaining small cone inner segments (prospective red/green cones). The rod inner segments are identifiable and show cilia. Between 19-20 and 24-25 weeks, the cone inner segments elongate and change in shape from spherical to oval. At 24-25 weeks, the outer segments develop from the distal ends of rod cilia. At this period, the inner segments of rods and cones are interconnected by protoplasmic projections. Although the precursors of both rods and cones appear to be in a similar state of development at 14-15 weeks gestation, the rods undergo morphological maturation earlier than do the cones. Photoreceptor development in the anterior retina lags behind that of the posterior retina by about 10 weeks. At 5 months after birth, the posterior retina possesses fully developed photoreceptors that are comparable to those of the adult. However, the photoreceptors in the ora serrata resemble those in the posterior retina of 24-25 weeks gestation.
Environmental scanning electron microscopic observations of Postia placenta grown on a defined medium and on red spruce wood allowed for the examination of the hydrated sheath of P. placenta. In the wood environment, mature hyphae that were not adhering to the substrate were observed to have a mycofibrillar morphology whereas hyphal tips and branch points had a smooth sheath morphology. A mycofibrillar adhesive matrix was observed on the hyphae growing on glass slides in the defined medium. These morphologies for hyphal sheaths in P. placenta are similar to those previously described by investigators from other laboratories who have used traditional electron microscopic preparative protocols that include dehydration steps. The potential future usefulness of environmental scanning electron microscopic technology in the study of the fine details of extracellular matrices is briefly discussed.
During this study, microtechnology and plasma etching were used to produce gratings 1.0 (TiD01), 2.0 (TiD02), 5.0 (TiD05), and 10.0 microns wide (TiD10) into commercially pure titanium wafers. After incubation of rat dermal fibroblast (RDFs) on these surfaces for 3 days, the cells were observed with scanning electron (SEM), transmission electron (TEM), and confocal laser scanning microscopy (CLSM). Results showed that the RDFs as a whole and their stress fibers oriented strictly parallel to the surface pattern on the TiD01 and TiD02 surfaces. On the TiD05 and TiD10 surfaces, this orientation was not observed. In addition, TEM and CLSM demonstrated that the focal adhesion points (FAP) were located mainly on the surface pattern ridges. TEM revealed that FAP were wrapped occasionally around the edges of the ridges. Only the RDFs on both the TiD05 and TiD10 surfaces protruded into the grooves and possessed FAP on the walls of the grooves. Attachment to the groove floor was observed only on the TiD10 textures. Comparison of these results with earlier observations on microtextured silicone rubber substrata suggests that material-specific properties do not influence the orientational effect of the surface texture on the observed RDF cellular behavior. The proliferation rate of the RDFs, however, seems to be much higher on titanium than on silicone rubber substrata.
In 1985 we developed an ultrahigh-resolution scanning electron microscope with a resolution of 0.5 nm. It is equipped with a field emission gun and an objective lens with a very short focal length. In this study we report a survey of some different preparation techniques and biological specimens using the new scanning electron microscope. Intracellular structures such as cell organelles were observed surprisingly sharper than those observed by ordinary scanning electron microscopes. However, at magnifications over 250,000 x, platinum particles could be discerned as scattered pebbles on the surface of all structures in coated materials. Using an uncoated but conductively stained specimen, we successfully observed ribosomes on a rough endoplasmic reticulum at a direct magnification of 1 million. In these images some protrusions were recognized on the ribosomes. Ferritin and immunoglobulin G were used as samples of biological macromolecules. These samples were observed without metal coating and conductive staining. The ferritin particles appeared as rounded bodies without any substructure on the surface and immunoglobulin G as complexes of three-unit bodies. In the latter the central body might correspond to the Fc fragment and two side ones to Fab fragments. We assume that ultrahigh-resolution scanning electron microscopy is an effective means for observation of the cell fine structures and biological macromolecules. It will open a new research field in biomedicine.
A scanning electron microscopic technique was used to investigate the surface structure of dentinogenically active odontoblasts. Thin pieces of rat incisors were fixed, rapidly frozen, freezedried at minus 70 degrees C and fractured to expose new surfaces prior to examination in the SEM. Differences in the appearance of odontoblastic cell surfaces were seen, with the most extensive ridge formations at the distal part of the sides of the odontoblasts. The predentine area displayed a spongy structure which contrasted to the compact appearance of dentine. Results are discussed in relation to previous studies at the light microscopic and transmission electron miscroscopic levels.
The crura of normal human stapes were studied with the scanning electron microscope. Three definite layers were seen: mucosal, periosteal, and bone. The appearance of each layer, as well as of the transition zones, has been presented. Familiarization with the scanning electron microscopic features of the normal human stapes crura should make identification and interpretation of abnormal features of diseased states apparent.
A hybrid scanning transmission electron microscope (STEM) and scanning tunneling microscope (STM) is described which allows simultaneous imaging of biological structures adsorbed to electron-transparent specimen supports in both modes of scanning microscopy, as demonstrated on uncoated phage T4 polyheads. We further discuss the reproducibility and validity of height data obtained from STM topographs of biomacromolecules and present raw data from topographs of freeze-dried, metal-coated nuclear envelopes from Xenopus laevis oocytes.