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Transmission Electron Microscopic Observations (transmission + electron_microscopic_observation)
Selected AbstractsEmbryonic erythropoiesis in human yolk sac: Two different compartments for two different processesMICROSCOPY RESEARCH AND TECHNIQUE, Issue 12 2008Jaime Pereda Abstract The wall of 12 yolk sacs (YSs) from 17- to 50-day-old human embryos was examined by light, scanning, and transmission electron microscopy to identify the ontogeny of embryonic erythropoiesis. Initial formation of blood island with the generation of erythroid and endothelial cells was seen in the mesenchymal layer in embryos aged 17 days. A network of blood vessels containing abundant erythroblasts was identified in the YS walls of embryos aged ,24 days. At this age, erythroblasts were also identified within the embryo body. Primitive erythroblasts were the only cells present within the embryo and its YS until the end of week 5. These cells first appeared in the mesenchymal vascular plexus of the YS wall, and were then observed in the liver and other tissues of the embryo. At embryonic week 5, two compartments were identified in the YS wall; a mesodermal one in which blood vessels were formed, and an endodermal compartment in which erythrocytes were present within the endodermal vesicles. Erythrocytes were small non-nucleated cells similar to adult erythrocytes. Transmission electron microscopic observation focused on the endodermal vesicles confirmed the presence of definitive erythrocytes only at such extra vascular location. At this age, there were no definitive erythrocytes detected within the embryo. Erythrocytes started to be identified in embryonic blood vessels from week 7 onward. These findings provide information not previously described about YS erythropoiesis during early human development. Microsc. Res. Tech., 2008. © 2008 Wiley-Liss, Inc. [source] Enzymatic oxidation products of spermine induce greater cytotoxic effects on human multidrug-resistant colon carcinoma cells (LoVo) than on their wild-type counterpartsINTERNATIONAL JOURNAL OF CANCER, Issue 1 2002Annarica Calcabrini Abstract The occurrence of resistance to cytotoxic agents in tumor cells, associated with several phenotypic alterations, is one of the major obstacles to successful anticancer chemotherapy. A new strategy to overcome MDR of human cancer cells was studied, using BSAO, which generates cytotoxic products from spermine, H2O2 and aldehyde(s). The involvement of these products in causing cytotoxicity was investigated in both drug-sensitive (LoVo WT) and drug-resistant (LoVo DX) colon adenocarcinoma cells. Evaluation of clonogenic cell survival showed that LoVo DX cells are more sensitive than LoVo WT cells. Fluorometric assay and treatments performed in the presence of catalase demonstrated that the cytotoxicity was due mainly to the presence of H2O2. Cytotoxicity was eliminated in the presence of both catalase and ALDH. Transmission electron microscopic observations showed more pronounced mitochondrial modifications in drug-resistant than in drug-sensitive cells. Mitochondrial functionality studies performed by flow cytometry after JC-1 labeling revealed basal hyperpolarization of the mitochondrial membrane in LoVo DX cells. After treatment with BSAO and spermine, earlier and higher mitochondrial membrane depolarization was found in LoVo DX cells than in drug-sensitive cells. In addition, higher basal ROS production in LoVo DX cells than in drug-sensitive cells was detected by flow-cytometric analysis, suggesting increased mitochondrial activity in drug-resistant cells. Our results support the hypothesis that mitochondrial functionality affects the sensitivity of cells to the cytotoxic enzymatic oxidation products of spermine, which might be promising anticancer agents, mainly against drug-resistant tumor cells. © 2002 Wiley-Liss, Inc. [source] Histological evaluation on bone regeneration of dental implant placement sites grafted with a self-setting ,-tricalcium phosphate cementMICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2008Masayoshi Nakadate Abstract This study aimed to evaluate the histological characteristics of the new bone formed at dental implant placement sites concomitantly grafted with a self-setting tricalcium phosphate cement (BIOPEX-R®). Standardized defects were created adjacent to the implants in maxillae of 4-week-old male Wistar rats, and were concomitantly filled with BIOPEX-R®. Osteogenesis was examined in two sites of extreme clinical relevance: (1) the BIOPEX-R®-grafted surface corresponding to the previous alveolar ridge (alveolar ridge area), and (2) the interface between the grafting material and implants (interface area). At the alveolar ridge area, many tartrate-resistant acid phosphatase (TRAPase)-reactive osteoclasts had accumulated on the BIOPEX-R® surface and were shown to migrate toward the implant. After that, alkaline phosphatase (ALPase)-positive osteoblasts deposited new bone matrix, demonstrating their coupling with osteoclasts. On the other hand, the interface area showed several osteoclasts initially invading the narrow gap between the implant and graft material. Again, ALPase-positive osteoblasts were shown to couple with osteoclasts, having deposited new bone matrix after bone resorption. Transmission electron microscopic observations revealed direct contact between the implant and the new bone at the interface area, although few thin cells could still be identified. At both the alveolar ridge and the interface areas, newly formed bone resembled compact bone histologically. Also, concentrations of Ca, P, and Mg were much alike with those of the preexistent cortical bone. In summary, when dental implant placement and grafting with BIOPEX-R® are done concomitantly, the result is a new bone that resembles compact bone, an ideal achievement in reconstructive procedures for dental implantology. Microsc. Res. Tech., 2008. © 2007 Wiley-Liss, Inc. [source] Synthesis and characterization of ,-Al2O3 nanorodsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2006W. F. Li Abstract One-dimensional nanorods of cubic aluminum oxide (,-Al2O3) have been synthesized by DC electric arc discharge of Fe and Al powders. It is seen that the diameters of the ,-Al2O3 nanorods are relatively uniform, ranging from 20 to 30 nm. On the basis of detailed transmission electron microscopic observation, it is proposed that the growth of a ,-Al2O3 nanorod follows the vapor,liquid,solid (VLS) process assisted by a two-dimensional vapor,solid (VS) nucleation and growth mechanism. The features of heavy twinning in the nanorod imply that twins might contribute to the growth of the nanorod and serve as the nucleus of the nanorod. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparative analysis of two biliproteins, BP1 and BP2, from haemolymph of cabbage white butterfly, Pieris rapaeARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 4 2006Chi Won Choi Abstract Two blue-pigment binding proteins, BP1 and BP2, are present in larval and pupal haemolymph of cabbage white butterfly, Pieris rapae, and fluctuate in expression during development. Both BP1 and BP2 are found in pupal haemolymph in varying proportions as well as in adult haemolymph, while only small amounts of BP2 are found in larval haemolymph. BPs are separated by 75% ammonium sulfate, and then purified effectively by ion exchange column chromatography and preparative gel electrophoresis. It was shown that BP1 and BP2 have molecular masses of 20,244 and 19,878 Da, and isoelectric points of 7.0 and 6.8, respectively. Considering their amino acid compositions and N-terminal amino acid sequences, the two proteins are almost identical except the first N-terminal amino acid. The first amino acid of BP1 is asparagine, whereas the initial residue of BP2 is aspartic acid. Anti-BP1 cross-reacts with BP2, indicating that they have immunological homogeneity. Western blotting analyses revealed that only BP1 was present in the larval tissues such as fat body, integument, muscle, and hindgut. However, BP1 was not found in midgut, Malphigian tubules, and silk gland. BP1 was also present in the protein bodies, and both cuticle and hemocoel sides of larval epidermis cells by the transmission electron microscopic observation. The information in this report will facilitate studies on the molecular biology and biological significance of insect BPs. Arch. Insect Biochem. Physiol. 61:220,230, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||