Search

We investigated the effects of targeted functionalized silica nanoparticles on the radiosensitivity of cancer cells. Better control of the local concentration of silica nanoparticles may facilitate their use as an adjuvant in conjunction with ionizing radiation to target cancer cells while preventing damage to normal cells. Hyperbranched polyamidoamine (PAMAM) was grafted onto the surface of amorphous silica nanoparticles to functionalize them. The PAMAM-coated silica nanoparticles (PCSNs) were then conjugated with fluorescent dyes. Anti-HER2 antibodies were covalently attached to the labeled PCSNs. The HER2-overexpressing SK-BR3 breast cancer cell line was incubated in medium containing the PCSN probes. After incubation; the cells were exposed to X-ray radiation. Cells were counted in all samples using cell proliferation assays; and apoptotic cells were detected. The cell survival results showed that the combination of the targeted PCSN probes and radiation reduced the survival rate of SK-BR3 cells to a greater extent than when either PCSN probes, PCSNs or radiation were applied individually. The results also showed an increase in apoptosis in the SK-BR3 cells that internalized the PCSN probes and were then irradiated. Based on these data, PCSN probes act as specific radiosensitizing agents for HER2-overexpressing cells.

Tooth enameloid in bony fish is a well-mineralized tissue resembling enamel in mammals. It was assumed that the dental epithelial cells are deeply involved in the formation of enameloid. However, unlike enamel matrix which fully consists of several ectodermal enamel matrix proteins (EMPs), whether enameloid matrix contains ectodermal EMPs has been debated for a long time. In the present study, transmission electron microscopy-based immunohistochemical examinations, using the protein A-gold method with antibodies and antiserum against mammalian amelogenin, were performed in order to search for EMP-like proteins in the cap enameloid of basic actinopterygians, Polypterus and gar. Positive immunoreactivity was detected in the cap enameloid matrix just before the appearance of many crystallites along collagen fibrils, indicating that the cap enameloid contains EMP-like proteins. Immunolabelling was usually found along the collagen fibrils but was not seen on the electron-dense fibrous structures. Therefore, it is conceivable that the ectodermal EMP-like proteins in cap enameloid are involved in crystallite formation along collagen fibrils.

The enameloid covering the surface of the teeth in bony fishes exhibits a very high degree of mineralization, and seems to have functions similar to the enamel in mammals. The aim of this study was to investigate the cellular control system of crystallization during enameloid formation. The enamel organs during the enameloid formation stages in ray-finned fishes were observed by transmission electron microscopy and enzyme cytochemistry, which detects hydrolytic enzyme activities. During the mineralization and maturation stages, many large and long crystals with a clear outline became packed densely in the enameloid. Infoldings of the distal plasma membrane in the inner dental epithelial (IDE) cells were marked, and many acid phosphatase positive lysosomes were present in the cytoplasm. The well-developed Golgi apparatus, and many cisternae of endoplasmic reticulum, secretory granules, mitochondria were visible in the IDE cells during these later stages. The activities of non-specific alkaline phosphatase, calcium-dependent adenosine triphosphatase and potassium-dependent p -nitrophenylphosphatase were usually detected at the plasma membrane of the IDE cells during the mineralization and maturation stages. These results suggest that the dental epithelial cells are mainly involved in the degeneration and removal of enameloid matrix and in material transportation during the enameloid mineralization and maturation stages, rather than in the formation of enameloid matrix.

An isolated upper fourth premolar (P4) of the extinct red panda Parailurus was recovered from the Pliocene (3–4 Ma) Ushigakubi Formation near Tochio, Niigata Prefecture, Japan. This is the first report of Parailurus from Asia, a genus previously known from Europe and northwestern North America. The Tochio P4 is about 50 percent larger than that of the extant Ailurus fulgens, lacks an entostyle, but has a lingual cingulum, protoloph with paraconule, a marked posterior cingulum with fine wrinkles, and a distal buccolingual groove. The transverse width of the P4 is greater than the anteroposterior length; the reverse is true of Parailurus anglicus from Europe.

Biomineralization is interpreted to be the mineral deposition occurred under the influence of organisms. To study biomineralization, it is quite important to perform biological techniques besides mineralogical ones, because biominerals are closely related to cells and organic materials. This article describes a series of biological techniques for biomineralization study using transmission electron microscopy, and shows some examples.

The mineralogy of sedimentary iron ores from the Gunma iron mine are described to evaluate the role of microorganisms and plants in ore formation. The iron ore is composed of nanocrystalline goethite, well-crystallized jarosite and very small amounts of strengite. The ore characteristically occurs as thick-bands of alternating goethite and jarosite bands, thin-bands of different goethite grain sizes, and fossil-aggregate ore rich in moss and/or leaves. Algal fossils are clearly preserved in the goethite bands in the thick-banded ore. Lattice imaging showed characteristic crystallographic orientations of the goethite nanocrystals. The thin-banded iron ores consist of micrometer-sized chestnut-burr-like goethite aggregates, probably formed by bacterial iron biomineralization. The bands may be attributed to biological or seasonal rhythms. Various products of biomineralization are found in the present-day pH 2‐3, Fe 21 -, and SO -rich streams. Bacterial precipitation had var22 4 iations from amorphous Fe-P-(S) precipitates near the outlet of mineral spring to Fe-P-S precipitates and to Fe-S-(P) (schwertmannite-like) precipitates in the midstream. Mosses and green algae are also collecting Fe precipitates in and around the living and dead cells. Comparison of the processes occurring in the present-day streams and the iron-ore specimens supports the interpretation of these ores as the product of biomineralization.

Background We propose a new approach to facilitate sentinel node biopsy examination by multimodality imaging in which radioactive and near-infrared (NIR) fluorescent nanoparticles depict deeply situated sentinel nodes and fluorescent nodes with anatomical resolution in the surgical field. For this purpose, we developed polyamidoamine (PAMAM)-coated silica nanoparticles loaded with technetium-99m (99mTc) and indocyanine green (ICG). Methods We conducted animal studies to test the feasibility and utility of this dual-modality imaging probe. The mean diameter of the PAMAM-coated silica nanoparticles was 30 to 50 nm, as evaluated from the images of transmission electron microscopy and scanning electron microscopy. The combined labeling with 99mTc and ICG was verified by thin-layer chromatography before each experiment. A volume of 0.1 ml of the nanoparticle solution (7.4 MBq, except for one rat that was injected with 3.7 MBq, and 1 μg of an ICG derivative [ICG-sulfo-OSu]) was injected submucosally into the tongue of six male Wistar rats. Results Scintigraphic images showed increased accumulation of 99mTc in the neck of four of the six rats. Nineteen lymph nodes were identified in the dissected neck of the six rats, and a contact radiographic study showed three nodes with a marked increase in uptake and three nodes with a weak uptake. NIR fluorescence imaging provided real-time clear fluorescent images of the lymph nodes in the neck with anatomical resolution. Six lymph nodes showed weak (+) to strong (+++) fluorescence, whereas other lymph nodes showed no fluorescence. Nodes showing increased radioactivity coincided with the fluorescent nodes. The radioactivity of 15 excised lymph nodes from the four rats was assayed using a gamma well counter. Comparisons of the levels of radioactivity revealed a large difference between the high-fluorescence-intensity group (four lymph nodes; mean, 0.109% ± 0.067%) and the low- or no-fluorescence-intensity group (11 lymph nodes; mean, 0.001% ± 0.000%, p < 0.05). Transmission electron microscopy revealed that small black granules were localized to and dispersed within the cytoplasm of macrophages in the lymph nodes. Conclusion Although further studies are needed to determine the appropriate dose of the dual-imaging nanoparticle probe for effective sensitivity and safety, the results of this animal study revealed a novel method for improved node detection by a dual-modality approach for sentinel lymph node biopsy.

Morphological features of the cap enameloid and dental epithelial cells were investigated by light and transmission electron microscopy during the various stages of enameloid mineralisation and early maturation in the tilapia. The pattern of mineralisation along collagen fibrils in the enameloid differed from that in the dentine. Many matrix vesicles were found in the predentine and in the enameloid, suggesting that they may be involved in the initial mineralisation in both regions. Most of the organic matrix disappeared from the cap enameloid during mineralisation and maturation. The disappearance of the organic matrix could be divided into 2 stages. Initially a fine network-like matrix, which probably consisted of glycosaminoglycans and extended between collagen fibrils, began to disappear. At the same time, fine crystallites and electron-dense, fine granular material covered the collagen fibrils as mineralisation of the enameloid began. In the second stage, the maturation of the enameloid, the collagen fibrils degenerated completely and disappeared from the cap enameloid, being replaced by large numbers of large crystals. At the mineralisation stage, the numbers of lysosomal bodies tended to increase in the inner dental epithelial (IDE) cells, which contained a well developed Golgi apparatus and rough endoplasmic reticulum (rER). At the early stage of maturation, a ruffled border was noted at the distal ends of the IDE cells, which contained many mitochondria and lysosomal bodies, but less rER. These features suggest that the cells actively absorb the organic matrix, which includes collagen fibrils, in the cap enameloid. The outer dental epithelial (ODE) cells were translucent cells that contained well developed labyrinthine canalicular spaces from the onset of the mineralisation stage to the middle stage of maturation. The IDE and ODE cells were clearly involved in the mineralisation of the cap enameloid at the mineralisation and maturation stages.

Histological examinations of erupted teeth and tooth germs in juvenile and adult dog salmon, Oncorhynchus keta, were carried out by light microscopy, scanning and transmission electron microscopy. As results of these observations, it was found that 1) cap enameloid may only be present in the teeth of juveniles and 2) the inner dental epithelial cells (i. d. e. cells) had great influence on the absorption of the majority of the cap enameloid matrix containing collagen fibers rather than on the formation of tooth matrix.In the teeth of juveniles, the tips of teeth were recognized as hypermineralized and collagen free portions by light microscopic, microradiographic, scanning and transmission electron microscopic observations. In the teeth of adults, however, no such features were seen in the tips of teeth. It seems that cap enameloid is absent in adult teeth.In the stage of matrix formation, the features of the inner dental epithelial cells (i. d. e. cells) indicated that the cells had begun their secretory activity. However, the morphological features of i. d. e. cells indicated that activity of the cells in matrix formation was at a low level and that a great quantity of epithelial secretions widely spread out in the tooth matrix was not obtained except around the basal lamina.On the contrary, active absorptive function at the distal margin of i. d. e. cells is expected and it is considered that absorption of organic substances from the cap enameloid area by i. d. e. cells had already begun in the late stage of matrix formation. Therefore, in the case of juvenile dog salmon, it is assumed that the i. d. e. cells play little part in the formation of tooth matrix and that the majority of the tooth matrix originates from the odontoblasts.In the stage of maturation, the taller and clear i. d. e. cells possessing a remarkable ruffled border at the distal margin were found in the portion surrounding the cap enameloid. It is assumed that such cells absorb the organic matrix containing collagen fibers from the cap enameloid area and make it a hypermineralized area. On the contrary, though the i. d. e. cells corresponding to collar enameloid became taller at this stage, the remarkable ruffled border was not found in these cells. The outermost layer of the collar enameloid area, about 0.5μm in thickness, became more electron-dense and the crystals, which appeared to be arranged perpendicular to the tooth surface, were gathered densely. Considerable difference in the formation mechanism may be present between cap and collar enameloid.

Histological examinations of tooth germs in juvenile dog salmon (chum salmon), Oncorhynchus keta, were carried out by transmission electron micoscopy in order to observe fine structures of initial calcification sites in dental matrix and to determine the relationship between electron-dense fibrous substances and matrix vesicles reported by Igarashi (1983). A number of matrix vesicles round or oval in shape and 300-700 A in diameter appeared in the apical dental matrix around the odontoblasts during the stage of matrix formation and about half of them contained more electron-dense crystal-like structures. On the other hand, matrix vesicles relatively decreased in number, but electron-dense fibrous substances consisting of flocculent substances and fine granular substances became well-developed and longer and increased in number in the apical dental matrix distant from the odontoblasts. These fibrous substances also contained more electrondense crystal-like structures. The stereophotographs showed that the fibrous substances exhibited filmy structures in three dimensions and continued to more electron-dense crystal-like structures. Moreover, the electron-dense fine granular substances would seem to attach to these filmy structures in parts. It seems that these filmy structures are the initial form of crystal. A number of matrix vesicles existed near the fibrous substances and some came into contact with the fibrous substances. A state indicative of the unit membrane of these matrix vesicles having broken and part of the contents disappeared was often obtained. It seems that these fibrous substances appeared later than matrix vesicles because of the observation in the early stage of matrix formation. These observations lead us to the conclusion that the fibrous substances derived from the contents of matrix vesicles. Fibrous substances indicated a positive reaction with ruthenium red staining. No fibrous substances appeared in the basal dental matrix during the stage of matrix formation in the basal portion in spite of the appearance of a number of matrix vesicles and small aggregates of crystal-like structures. It seems that this difference is closely concerned with the fact that the apical dental matrix is the initial portion to begin the calcification of tooth.

The tooth plates in the living Holocephalan, Chimaera phantasma were studied by various techniques. They consisted of osteodentin and hypermineralized pleromin (kosmin). The degree of mineralization on the latter was as much as in the enameloid of Chondrichthyes and Osteichthyes. Scanning electron microscope observation indicated that the pleromin consisted of large and granular crystals. X-ray powder diffractometry, electron microprobe analysis and analytical electron microscopy revealed that the inorganic constituent of pleromin included, as an essential element, a beta-Ca3(PO4)2 (whitlockite) structure containing a small amount of Mg.

In this paper, the eleven molars of four Asiatic elephants (Elephas maximus LINNE) in two zoos are described. They were found in the straw where the elephants slept, except one premolar, artificially removed just before shedding.Compared with the molars in function, the shed molars exihibit the following: smaller number of lamellae, shorter crown length, lower crown height by abrasion, resorbed roots, smooth mesial wearing surface with shallow dentin inlets and indistinct enamel foldings and broad distal facette. Root resorption is more evident in the mesial portion than in the distal; the buccal and lingual third parts are more resorbed than the intermediate third portion, on the buccal side in the upper molar and on the lingual side in the lower molar, than the opposite sides in basal aspect.It is shown in specimens no. 6 and 7 that the crown height decreased by 14-15mm through abrasion during three years (P1. I, 1-4). It was noted that the distal lamellae, (specimen no.11) were shed three months earlier than the mesial ones (specimen no.10, P1. I, 5-7)