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The endoplasmic reticulum (ER) is the largest membranous network serving as a region for protein, lipid and steroid synthesis, transport and storage. Detailed information about ER-cisternae, ER-tubules and rough endoplasmic reticulum (rER) is scarce in human blood cells. This study describes a series of giant inclusions and Auer bodies in promyeloblasts in six patients with acute promyelocytic leukemia (APL), by light microscopy, transmission electron microscopy (TEM) and cytochemical stains. TEM revealed that giant inclusions and pro-Auer bodies were associated with rER and surrounded by tubular structures composed of degenerated or redundant membrane in promyeloblasts, which corresponded with elements of the ER system. This paper reveals that in the promyeloblasts of APL, ER is the source of and transforms progressively into giant inclusions and Auer bodies. [ABSTRACT FROM AUTHOR]

The monocytes in acute monocytic leukemia (AML-M5b) were analyzed by scanning and transmission electron microscopy (SEM and TEM) to understand more fully their structure and origin. By SEM, monocytes exhibited localized expansions of the surface, some of which appeared to bud off as surface vesicles (SVs). Filopodial processes and pseudopodia were also present. TEM demonstrated that the SVs were composed of a double-membrane at the pole away from the cell body, and a single membrane nearer to the cell body. In the peripheral cytoplasm, intracellular vesicles (IVs) had the appearance of vacuoles and were enclosed by single membranes. Most SVs were characterized by a notch as a rER edge and an expanded head. Filopodial processes had the same thickness of 40 nm as the SV walls, which suggested a close developmental relationship between the two. Pseudopodia between SVs were irregular in size. Rod-like rER cisternae were prominent in the peripheral cytoplasm and some showed a close physical juxtaposition as to suggest a transition from rER to IVs to SVs. Ultrastructural cytochemistry demonstrated activity of 5'-nucleotidase over rER, SVs, filopodial processes and pseudopodia, and a patchy reaction over other areas of plasma membrane. Overall, the results indicated that rER transforms into SVs, filopodial processes and pseudopodia, as a way of integrating cytoplasmic membranes into the plasma membrane. [ABSTRACT FROM AUTHOR]

Fascia lata is an important element of the fascial system, which forms the continuum of connective tissue throughout the body. This deep fascia envelops the entire thigh and hip area and its main function is to transmit mechanical forces generated by the musculoskeletal system of the lower extremities. Fascia lata is also known as a useful and easily harvested graft material. Despite its crucial role in lower extremity biomechanics and wide-ranging applications in plastic and reconstructive surgery, both the structure of fascia lata and particularly the cells populating this tissue are relatively unexplored and therefore poorly understood. The aim of this study was to characterize the main cell populations encountered within human fascia lata and to try to understand their role in health and diseases. Pathologically unchanged human fascia lata was obtained post mortem from adult males. The specimens were analyzed under light, electron, and confocal microscopy. On the basis of different visualization techniques, we were able to characterize in detail the cells populating human fascia lata. The main cells found were fibroblasts, fibrocytes, mast cells, cells showing myoid differentiation, nerve cells, and most interestingly, telocytes. Our results supplement the formerly inadequate information in the literature regarding the cellular components of deep fascial structure, may contribute to a better understanding of the pathogenesis of fascial disorders and improve fascia lata application as a graft material. [ABSTRACT FROM PUBLISHER]

To identify the nature of foam cells in atherosclerosis, carotid atherosclerotic plaques (CAPs) from six patients were studied. Hematoxylin-and-eosin, Congo Red and Oil Red O staining were used to study histopathologic alterations in CAPs. CD31, α-smooth-muscle actin (α-SMA), CD68, desmin and S100 were stained immunohistochemically. The ultrastructure of foam cells was analyzed by transmission electron microscopy (TEM). CAPs were shown to be composed of a fibrous cap covering a dome-shaped mass with a peripheral, circumferential fringe merging with a basal band which itself met the tunica media, the latter consisting of smooth-muscle cells (SMCs). The interior of the dome-shaped mass exhibited fibrosis, neovascularization, hemorrhage, necrosis and calcification. Lipid droplets identified by histological stains and TEM were found in the rounded epithelioid foam cells regarded as macrophages, as well as in spindled cells interpreted here as lipoleiomyocytes (lipid-containing SMCs), lipofibroblasts and lipomyofibroblasts; and all these cells were located in different regions of the CAPs. All of these lipid-laden cells were strongly positive for CD68 but negative for desmin. Foam cells were weakly positive for α-SMA, CD31 and S100. The results indicate that the light microscopically identifiable population of foam/lipid-laden cells hide a spectrum of diverse differentiation ranging from the expected macrophage phenotype to non-macrophage phenotypes. The origin of these diverse cell phenotypes in terms of multipotential mesenchymal precursors and the origin of the intracellular lipid are discussed. [ABSTRACT FROM AUTHOR]

To clarify the characteristics and origin of the cellular components in atherosclerosis, carotid atherosclerotic plaques (CAPs) of four patients were studied by light microscopy using hematoxylin-eosin, Congo red and alpha-smooth-muscle actin stains, and by transmission electron microscopy of different regions of CAPs. By light microscopy, CAPs were composed of 1) a fibrous cap; 2) an atherosclerotic core presenting focal fibrosis, neovascularization, hemorrhage, necrosis, chondrification and ossification; and 3) a basal band composed of a hyperplasic pseudo-media and affected tunica media. Ultrastructurally, the CAPs contained a diversity of cells including fibroblasts, myofibroblasts, osteochondrocytes, vascular smooth-muscle cells, foam cells and other myoid cells characterized by varied features of the above mentioned cells. The results indicated that CAPs were derived from a proliferation of multipotential mesenchymal stem cells, leading to the presence of degenerated foam cells and lipid-laden cells. [ABSTRACT FROM AUTHOR]

Megakaryocytes engage in the synthesis of a variety of molecular and macromolecular constituents to build-up characteristic megakaryocyte structure and form proplatelets in a series of cells from megakaryocyte precursors to the fully matured cell. The process is illustrated in this review by light microscope morphology and transmission electron microscopy, which emphasizes new findings in human in vivo megakaryocytes, thereby making a contrast with the abundant literature on megakaryocytes from experimental animal and human in vitro material. Four stages are identified and described, based on the development of characteristic structures including α-granules, dense granules (dense-core granules), the demarcation membrane system (DMS), and proplatelets. The mechanism of DMS development is discussed, in terms of hypotheses suggesting origin from the plasma membrane, and contributions of membrane from the Golgi apparatus and endoplasmic reticulum. The formation of the marginal zone is also discussed, which is suggested to result from a circumscription of the peripheral organelle-free cytoplasmic fringe by peripheral circular cytoskeletal elements such as cytoplasmic actin and microtubules. [ABSTRACT FROM AUTHOR]

Object: To study the relationship between monocyte/histiocyte activation and myelodysplastic syndrome (MDS). Methods: Analyzing ultrastructure and myeloperoxidase reaction of nucleated cells in bone marrow from 59 cases of MDS by transmission electron microscopy. Four groups of MDS were subdivided on the basis of their content of activated inflammatory cells - morbid hematopoiesis with minimal inflammatory cell activation (MH-MICA); MDS with monocytic system activation (MSA); MDS with lymphocyte activation (LCA); and MDS with granulocyte activation (GCA). Results: About 20, 22, 7, and 10 cases were classified as MH-MICA (34%), MSA (37%), LCA (12%), and GCA sub-types (17%), respectively. About 3, 5, 0, and 3 cases from MH-MICA, MSA, LCA, and GCA, respectively, underwent leukemic transformation within 2 years. Conclusion: The findings suggest that activation of inflammatory cells in bone marrow is an important feature of MDS, and that monocytes/histocytes are perhaps the most prominent cellular participants in the pathogenesis of MDS. [ABSTRACT FROM AUTHOR]