Morphological Characterization of Basally Located Uninucleate Trophoblast Cells as Precursors of Bovine Binucleate Trophoblast Giant Cells

Binucleate trophoblast giant cells (TGCs) are one characteristic feature of the ruminant placenta. In cows, the frequency of TGCs remains constant for most of the duration of pregnancy. As TGCs are depleted by their fusion with uterine epithelial cells, they need to be constantly formed. It is still unclear whether they develop from stem cells within the trophectoderm or whether they can arise from any uninucleate trophoblast cell (UTC). Within the latter, generally accepted theory, a basally located uninucleate cell (BUC) without contact to the feto-maternal interface would represent a transient cell between a UTC and a TGC. So far, no evidence for the existence of such transient cells or for the presence of stem cells has been shown. The aim of the present study is to morphologically characterize the early stages of TGC development. Placentomal tissue of 6 pregnant cows from different gestational stages (gestational days 51-214) was examined for BUCs, UTCs, and TGCs either in serial sections (light and transmission electron microscopy, TEM, n = 3), in single sections (TEM, n = 2), or by serial block face-scanning electron microscopy (n = 1). These investigations revealed the occurrence of BUCs, as well as young TGCs showing contact with the basement membrane (BM), but without apical contact to the feto-maternal interface. The study morphologically defines these 2 cell types as early stages of TGC development and shows that binucleation of TGCs can precede detachment from the BM.

Breast Carcinoma with Osteoclast-Like Giant Cells: Immunohistochemical and Ultrastructural Study of a Case and Review of the Literature

We describe an unusual case of infiltrating ductal carcinoma, not otherwise specified, containing numerous benign stromal osteoclast giant cells (OGCs). Macroscopically, the tumor appeared as a well-outlined dark brown mass and was initially interpreted as a benign lesion on the mammograms. OGCs were uniformly distributed in the tumor and were found in vascularized, hemorrhagic stroma often abutted on the nests of tumor cells. Electron microscopy supported a histiocytic origin of the OGCs, but immunohistochemistry failed to confirm the observation. The patient was alive and well 30 months following the operation. A review of the literature concerning breast carcinoma with OGCs is also presented.

Differentially-dimensioned furrow formation by zygotic gene expression and the MBT

Despite extensive work on the mechanisms that generate plasma membrane furrows, understanding how cells are able to dynamically regulate furrow dimensions is an unresolved question. Here, we present an in-depth characterization of furrow behaviors and their regulation in vivo during early Drosophila morphogenesis. We show that the deepening in furrow dimensions with successive nuclear cycles is largely due to the introduction of a new, rapid ingression phase (Ingression II). Blocking the midblastula transition (MBT) by suppressing zygotic transcription through pharmacological or genetic means causes the absence of Ingression II, and consequently reduces furrow dimensions. The analysis of compound chromosomes that produce chromosomal aneuploidies suggests that multiple loci on the X, II, and III chromosomes contribute to the production of differentially-dimensioned furrows, and we track the X-chromosomal contribution to furrow lengthening to the nullo gene product. We further show that checkpoint proteins are required for furrow lengthening; however, mitotic phases of the cell cycle are not strictly deterministic for furrow dimensions, as a decoupling of mitotic phases with periods of active ingression occurs as syncytial furrow cycles progress. Finally, we examined the turnover of maternal gene products and find that this is a minor contributor to the developmental regulation of furrow morphologies. Our results suggest that cellularization dynamics during cycle 14 are a continuation of dynamics established during the syncytial cycles and provide a more nuanced view of developmental- and MBT-driven morphogenesis.

One of the primary events that must occur repeatedly throughout a complex animal’s lifetime is the ingression of a plasma membrane furrow. Furrow formation and ingression are requisite elements of cell division, and drive the physical separation of one cell into two cells. However, the mechanisms that permit an embryo to change the length and size of a furrow are unclear. Here, we show that a combination of higher ingression rates and longer duration phases drive changes in furrow dimensions through the introduction of a new ingression phase. These changes are driven by the embryo’s own genome, and suggest that zygotic transcription controls organismal form at an earlier time point than previously appreciated. Additionally, the failure to properly lengthen furrows as development proceeds causes defects in chromosome segregation during cell division and results in massive genomic instability. Our data demonstrate the importance of the dynamic regulation of furrow dimensions to organismal form and viability.

In Vivo Imaging of Microtubule Organization in Dividing Giant Cell

Mitosis which is a major step during plant development can also be observed in physiopathological conditions. During the compatible interaction between the root-knot nematode Meloidogyne incognita and its host Arabidopsis, the pathogen induce through repeated divisions without complete cytokinesis the formation of hypertrophied and multinucleate feeding cells, named giant cells. Due to the presence of hypertrophied plant cell material surrounding the giant cells, classical live cell imaging gave therefore very poor resolution. Here, we describe a protocol which allows the in vivo observation of the mitotic apparatus in developing giant cells using confocal imaging of vibrosliced tissues. This approach can also be used to visualize in vivo other cellular processes occurring in different steps of giant cells.

Polyploidization on SK-N-MC human neuroblastoma cells infected with herpes simplex virus 1

Polyploidization is one of the most dramatic changes occurring within cell genome owing to various reasons including under many viral infections. We examined the impact of herpes simplex virus-1 (HSV-1) on SK-N-MC human neuroblastoma cell line. The infected cells were followed from 6 hours up to 96 hours post infection (hpi). A large number of polyploid cells with giant nuclei was observed under the influence of HSV-1 at 24 hpi with the DNA content of 32c to 64c or more, in comparison with control SK-N-MC cells that were characterized by relatively moderate values of ploidy, i.e. 8с to 16с (where 1c is the haploid amount of nuclear DNA found in normal diploid populations in G0/G1). After 48-96 hpi, the population of polyploid cells with giant nuclei decreased to the benchmark level. The SK-NMC cells infected with HSV-1 for 24 hours were stained with gallocyanine and monitored for cytological features. The infected cells underwent virus induced cellcell and nuclei fusion with the formation of dense nuclei syncytium. The metabolic activity of HSV-1 infected cells was higher in both nuclei and nucleoli when compared to control cells.

[Histological and ultrastructural features of giant cell myocarditis: report of 3 cases]

OBJECTIVE

To identify clinical and pathological features of giant cell myocarditis.

METHODS

Clinical presentation and follow-up data of three patients with giant cell myocarditis were collected.Gross, histopathological, immunohistological and ultrastructural findings of extransplantated hearts of the patients were documented.

RESULTS

Grossly, multifocal involvement of the myocardium with variably dilated cardiac chambers were observed in all 3 cases.Histological examination revealed pronounced focal inflammatory infiltrates with multinucleated giant cells. Multinucleated giant cells were positive for CD68 and CD11b immunostains but were negative for CD163 in all cases. Transmission electron microscopy showed that the multinucleated giant cells derived from fusion of several macrophages with adherent lymphocytes and secretary cells. Clinically, the overall patient condition improved in all three cases after heart transplantation.One patient experienced acute cellular rejection (2R level) 4 months after transplantation, but recovered after treatment. One patient developed multinucleated giant cells observed in heart biopsy two weeks after transplantation.

CONCLUSIONS

Giant-cell myocarditis is a rare disease of adult, and cardiac transplantation could improve the clinical outcome. Multinucleated giant cell in the myocarditis lesions were derived from macrophages, likely participating in the immune response. Endomyocardial biopsy is important for the diagnosis of giant cell myocarditis.

[ULTRASTRUCTURE OF PARENCHYMA IN THE SYNCYTIAL DIGESTIVE SYSTEM IN TURBELLARIA Convoluta convoluta (Acoela]

The paper presents data on the ultrastructure of parenchyma that is involved in the digestion in turbellaria Convoluta convoluta (n = 15). Unusual connections between the nuclear envelope, endoplasmic reticulum and plasma membrane of parenchymal cells were found for the first time, which may indicate the origin of these cell structures. The double trophic role of zooxanthellae in the organism of Convoluta is described.

CoCl2, a mimic of hypoxia, induces formation of polyploid giant cells with stem characteristics in colon cancer

The induction of polyploidy is considered the reproductive end of cells, but there is evidence that polyploid giant cancer cells (PGCCs) contribute to cell repopulation during tumor relapse. However, the role of these cells in the development, progression and response to therapy in colon cancer remains undefined. Therefore, the main objective of this study was to investigate the generation of PGCCs in colon cancer cells and identify mechanisms of formation. Treatment of HCT-116 and Caco-2 colon cancer cells with the hypoxia mimic CoCl₂ induced the formation of cells with larger cell and nuclear size (PGCCs), while the cells with normal morphology were selectively eliminated. Cytometric analysis showed that CoCl₂ treatment induced G2 cell cycle arrest and the generation of a polyploid cell subpopulation with increased cellular DNA content. Polyploidy of hypoxia-induced PGCCs was confirmed by FISH analysis. Furthermore, CoCl₂ treatment effectively induced the stabilization of HIF-1α, the differential expression of a truncated form of p53 (p47) and decreased levels of cyclin D1, indicating molecular mechanisms associated with cell cycle arrest at G2. Generation of PGCCs also contributed to expansion of a cell subpopulation with cancer stem cells (CSCs) characteristics, as indicated by colonosphere formation assays, and enhanced chemoresistance to 5-fluorouracil and oxaliplatin. In conclusion, the pharmacological induction of hypoxia in colon cancer cells causes the formation of PGCCs, the expansion of a cell subpopulation with CSC characteristics and chemoresistance. The molecular mechanisms involved, including the stabilization of HIF-1 α, the involvement of p53/p47 isoform and cell cycle arrest at G2, suggest novel targets to prevent tumor relapse and treatment failure in colon cancer.

[Isolation, culture and identification of human odontoclasts]

OBJECTIVE

To isolate, culture and identify odontoclasts in vitro and to establish a method of culturing human odontoclasts.

METHODS

Healthy and retentive deciduous teeth were extracted, and then placed in α-minimum essential medium containing 0.1% collagenase and 0.2% dispase for 1 h.Odontoclasts were obtained and incubated from the absorbing root surfaces of deciduous teeth.Isolated cells were viewed by inverted phase contrast microscope firstly. Then, the isolated odontoclasts were morphologically observed by hematoxylin and eosin staining (HE) and tartrate-resistant acid phosphatase (TRAP) staining. The prepared teeth slices were cocultured with the isolated odontoclasts and scanning electronic microscope(SEM) was used to demonstrate the presence of resorption lacunae.

RESULTS

The isolated odontoclasts appeared as multinucleated giant cell with many vacuolus in cytoplasm. TRAP staining demonstrated that the cytoplasm of the odontoclasts was full of claret-red positive particles.Resorption lacunae on teeth slices which cocultured with odontoclasts were seen under SEM.

CONCLUSIONS

Enzyme digestion is an effective method to isolate odontoclasts from absorbing root surface of deciduous teeth.

Microtomographic and morphometric characterization of a bioceramic bone substitute in dental implantology

In recent years, bone tissue regeneration studies have led to a deeper knowledge of chemical and structural features of the best biomaterials to be used as replacements for lost bone structures, with the autologus bone still today the only graft material able to ostegenerate, osteinduct and/or osteoconduct. The difficulties of the small available amount of autologus bone, together with morbidity of a second surgical operation on the same patient, have been overcome using both synthetic and biologic substitute bones. The possibility of investigating morphometric characteristics of substitute bones makes it possible to evaluate the predictability of regenerative processes and, so far, a range of different methods have been used for the purpose. X-ray microtomography (micro-CT) is a miniaturized form of conventional tomography, able to analyze the internal structure of small objects, performing three-dimensional images with high spatial resolution (< 10 micron pixel size). For a correct analysis, samples need not be altered or treated in any way, as micro-CT is a non-invasive and non-destructive technique. It shows promising results in biomaterial studies and tissue engineering. This work shows the potential applications of this microtomographic technique by means of an in vitro analysis system, in characterizing morphometric features of human bone tissue, and contributes to the use of this technique in studies concerning biomaterials and bioscaffolds inserted in bone tissue.

[Cytotomy in multinucleated epithelial cells under experimental conditions]

Multinucleated cell (MNC) cytotomy was studied in the epithelia with different functions (lining and glandular). Methods of light and electron microscopy were used to study MNCs in parietal peritoneum mesothelium of albino mice and in acinar-insular ("mixed") pancreatic cells of albino rats. Mesothelium was studied in film preparations, in which cell boundaries were demonstrated by silver nitrate. "Mixed" cells were studied by electron microscopy. Mice were injected with 0.4% hydrochloric acid, while rats were administered 40% glucose solution. MNCs in the epithelia studied were shown to be divided into cell territories, each consisting of a nucleus surrounded by the cytoplasm. These territories differed from each other by their structure and, therefore, by their functions. The appearance of plasma membranes between these cytoplasmic areas separating them into mononuclear cells or smaller MNCs, is described.

[Syncytial perforations of human neuronal embryo membranes]

An electron microscopy study of the anlage of cerebral cortex of human embryo has been carried with the aim of determining the presence of syncytial interneuronal connections in embryogenesis. It has been determined that, in part of the neurons, the glial embryo is absent and their external cell membranes are directly attached to each other by forming elongated or dotted tight junctions. Sometimes these junctions are perforated and, on their basis, the true syncytial interneuronal connections are formed. Natural structural properties of these connections are the following: formation of the base of tight membrane contacts, obligatory rounding of perforation edges, and the presence of residual particles in the form of spherical vesicles in the lumen of perforations. Results obtained allowed us to conclude that, in the anlage of cerebral cortex of embryos obtained during surgical abortion of pregnancy, apart from the formation of synaptic contacts, or until their formation, there is the possibility of syncytial interneuronal connections appearing. This should be considered during the transplantation of the developing brain.

[Fusion of brain neurons in rat embryos]

Syncytial interneuronal connections were studied in the sensomotor cortex and caudate nucleus of twenty 14-22 day rat embryos. It was shown that with the extremely weak development of glial processes, many neuronal bodies and their processes were in the direct contact with each other. The contacting membranes in these areas formed oblong and dot-like contacts resembling gap and tight junctions. As a result, the intercellular cleft experienced varicose-like deformations. In the area of contacts, barely visible membrane pores were formed that broadened to form large perforations. The perforation margins presented the rounded shape of fused plasma membranes of adjacent neurons. Inside the perforations, residual vesicular membranous bodies were formed. The areas of the paired membranes between perforations were fragmented, thus increasing the number of residual vesicles, until the neurons fused with each other completely by unifying the neuroplasm of contacting cells. The results of these studies suggest that that the fusion of neurons in vertebrate brain cortex and brainstem nuclei could occur not only in pathology, but also in normal animals at the stage of embryonic development.

[Fusion of frog cerebellar granule cells induced by toxic effects of glutamate and NO-generating compound]

The ultrastructural changes of cerebellar granule cells were studied under stroke modeling conditions, after the toxic effects of glutamate (Glu) and NO-generating compound. Glu toxic doses were shown to induce two types of nuclear chromatin changes. In some cases, the appearance of practically completely decondensed nuclear chromatin was detected, while in the others the nuclei contained partially decondensed chromatin. Pathological fusion of granule cells was observed in both cases. The toxic effect of NO-generating compound on granule cells also caused the appearance of the cells with both completely and partially decondensed (flocculent) chromatin. Granule cells with different chromatin type were able to fuse with each other. Thus, Glu and NO, causing changes in nuclear chromatin, activate the processes of cell clustering with the following cytoplasmic fusion and the formation of multinuclear conglomerates. The possible physiological role of granule cells fusion induced by high concentrations of Glu and NO-generating compound is discussed. This process is considered as a realization of the compensatory-adaptive reactions under extreme conditions observed in the stroke and oxidative stress.

[Glio-neuronal and glio-glial syncytial cytoplasmic connections in peripheral nerve trunks of the crayfish Astacus leptodactylus]

The paper considers various aspects of glial sheaths of neuritis in the crayfish peripheral nerve trunks and roots. There are revealed dotted glio-neurite tight junctions and a varicose deformation of the intercellular glio-neurite cleft. Rupture of membranes in the area of contact leads to formation of the glio-neurite pore (less than 10 nm) that is enlarged and forms wide (up to 240 nm) syncytial perforations. At the edge of perforation, either remnants of tight junctions are present or damaged membranes that fuse and are rounding. The lumen of perforations always contains residual membranous bodies in the form of vesicles. Their deviation from the median line can indicate a mutual translocation of substances of the glio- and neuroplasm. In the adjacent layers of the multilayer glial sheath there is noted a similar phenomenon of formation of the glio-glial syncytial connection terminating by fusion of neighbor glial layers, which is terminated by fusion of neighbor glial layers into the single lamina. The process begins from the varicose deformation of interglial clefts, which appears as a result of massive formation of dotted and expanded tight membranous contacts. As a result of transformation of ellipsoid varicose deformations into the spherical ones, syncytial pores (less than 10 nm) between them are formed, which are enlarged and break the paired gliolemmas into fragments. As a result, the adjacent glial layers are united. Since this process in intact animals occurs on the background of undamaged nerve structures, a suggestion is put forward about its reversibility and the functional nature.

[Experimental modeling and the discussion on the syncytial connections in the nervous system]

To solve the problem of the possibility of syncytial connection in the nervous system, this paper for the first time presents the evidence of experimental syncytial fusion of neurons. Neurons, isolated from the ganglia of the mollusc Lymnaea stagnalis and freed from the surrounding glia by pronase treatment, were drawn together by centrifugation and were kept in the culture medium for two days in the aggregated state. The neurons preserved the ability to generate normal processes. At the borders of adjacent cells, contacting mutual protrusions (feet) were formed that were separated from each other by vacuole-like enlargements of the intercellular clefts. Using the electron microscope, it was shown that at the borders of contacting feet the external cell membranes were destroyed. Only residual fragments of the destroyed membranes were detected. The cytoplasm of one adjacent cell was continuous with the cytoplasm of the other. Thus, the experiments confirm once more the correctness of the cell theory concerning the common main properties of all the cells and expand the concepts of the neuronal theory by the statement that in the nervous system, along with chemical synapses and electrical membrane contacts, the syncytial interneuronal connections are also possible.

[Contribution to the discussion on syncytial connections in the nervous system]

The paper discusses data on the existence of the syncytial interneuronal connections. Firstly, the discovery of synapses in principle is not a proof of the absence of syncytial connections in the nervous system. Secondly, there is a light microscopical evidence of the existence of the syncytial connections. These are found in giant axons of crustaceans, polychaetes, and other invertebrates, as well as during similar fusion of 2-3 processes into one fiber covered with myelin sheath in vertebrate neurons. In tissue culture, after the destruction of the neuronal body, its process connected to another neuron does not die, as it has syncytial connection with the latter. Thirdly, under the electron microscope, interneuronal syncytial connections were demonstrated in piglet intramural nervous system, in cat caudal mesenteric ganglion, in rabbit and frog hippocampus and cerebellum, and in cat cerebral cortex. Structural regularities of such connections have been described. By observing changes of contacting membranes in pathology, it was established that the essence of the process consists in a modification of tight junctions which are not refuted by anyone. The syncytial pores and perforations are also observed in intact animals in neurons without obvious lesions.

[Cytoplasmic syncytial connection--one of three forms of interneuronal connection]

The paper is a review of the current state of the important theoretical problem of neurophysiology about the principal possibility of the existence in the nervous system, apart from the major synaptic and contact connections, also of the cytoplasmic syncytial interneuronal connection. Also analyzed are electron microscopy data and results of observation on behavior of living neurons in tissue culture, which allow suggesting the existence in some loci of the nervous system and under certain conditions of the third form of syncytial interneuronal interactions. Regular signs of syncytial perforations are their formation on the ground of membrane contacts and the presence of rounded layers of fused membranes in the zone of defect and of residual membrane structures in the lumen of the perforations. Syncytial connections are formed only in the places, in which glia is absent. In other areas of neuronal bodies or processes, such perforations have never been revealed. The appearance of the cytoplasmic connections in some parts of the nervous system and at certain periods of its development undoubtedly produces an essential effect on functional properties of these parts.

Malignant Fibrous Histiocytoma of Bone: An Ultrastructural Study

An ultrastructural study of a case of malignant fibrous histiocytoma of bone in a 16-year-old skeletally mature female is presented. There were multiple metastatic bone lesions and a marked hypercalcemia. The cell population was similar to that found in soft tissue malignant fibrous histiocytoma lesions and comprised undifferentiated cells, fibroblastlike cells, histiocytes, and multinucleated giant cells. Occasional myofibroblasts and transitional cells with histiocytic and fibroblastic components were seen. The histiocytes were characterized by prominent Golgi bodies. Although there were many fibroblastlike cells, the rough endoplasmic reticulum was rarely as extensive or as well organized as in normal fibroblasts. The giant cells did not have the ultrastructural characteristics of osteoclasts, i.e., the clear zones and ruffled borders. Zonula adherens (belt desmosome) junctions were seen, but in general, intercellular junctions were poorly developed as to length and extent.

Ultrastructural Cytochemical and Ultrastructural Morphological Differences Between Human Multinucleated Giant Cells Elicited by Wear Particles from Hip Prostheses and Artificial Ligaments at the Knee

The authors investigated the ultrastructural cytochemical features of multinucleated and mononuclear cells in periprosthetic tissues associated with bone resorption (osteolysis) and those in tissues adjoining failed artificial ligaments having no relation to bone resorption. Clinical specimens of granulation tissue of each type, respectively numbering 4 and 3, were stained for tartrate-resistant acid phosphatase (TRAP) reactions and examined by light and electron microscopy. Both periprosthetic granulation tissues and those adjoining artificial ligaments contained TRAP-positive multinucleated and mononuclear cells. Near joint prostheses, multinucleated cells, including some giant cells, showed TRAP activity and cytoplasmic features resembling osteoclasts, while others had features consistent with foreign-body giant cells, and still others showed degenerative changes. Near artificial ligaments, TRAP-positive multinucleated cells lacked osteoclastic features. At both sites, TRAP-positive multinucleated cells had phagocytised wear particles. TRAP-positive mononuclear cells at both sites also showed phagocytic cytoplasmic features, but not osteoclastic cytoplasmic features. Human mononuclear phagocytes and multinucleated giant cells induced by wear particles possess TRAP activity. Those multinucleated giant cells at sites of osteolysis developed osteoclastic cytoplasmic features and have a phagocytic function.

Pleomorphic Xanthoastrocytoma: Report of a Case with Light and Electron Microscopy

A case of pleomorphic xanthoastrocytoma is reported with light and electron microscopic findings. This unusual tumor arose in a 15-year-old male. The tumor consisted predominantly of nests of xanthomatous cells and plump spindle cells surrounded by a prominent reticulin network. There was considerable cellular pleomorphism with abundant bizarre giant cells and multinucleated cells. Occasional mitoses were present. Electron microscopy and immunoperoxidase localization of glial fibrillary acidic protein (GFAP) confirmed the glial nature of the tumor. Recognition of this tumor is important. Despite its "m alignant" appearance, the tumor characteristically has a relatively good prognosis and should not be confused with high-grade gliomas or meningeal sarcomas, which require aggressive therapy.

Similarities Between Giant Cell Tumor of Bone, Giant Cell Tumor of Tendon Sheath, and Pigmented Villonodular Synovitis Concerning Ultrastructural Cytochemical Features of Multinucleated Giant Cells and Mononuclear Stromal Cells

The authors investigated ultrastructural cytochemical features of multinucleated and mononuclear stromal cells in giant cell tumor of bone (GCTB), giant cell tumor of tendon sheath (GCTTS), and pigmented villonodular synovitis (PVNS). Specimens of each tumor, respectively numbering 4, 4, and 3, were stained for tartrate-resistant acid phosphatase (TRAP) reactions and examined with an electron microscope. In GCTB and GCTTS, multinucleated cells, including some relatively small giant cells, showed TRAP activity and cytoplasmic features characteristic of osteoclasts, and also sometimes abundant rough endoplasmic reticulum and siderosomes. A few giant cells with macrophage-like features and slight TRAP activity were demonstrated in GCCTS and PVNS. In each tumor type, mononuclear cells showing TRAP activity shared cytoplasmic features with osteoclast-like multinucleated giant cells, while some others had macrophage-like features, and still others were poorly differentiated; a few mononuclear cells showed cell-to-cell contact. Ultrastructural similarities of TRAP-positive mononuclear cells in the three tumor types, and those between TRAP-positive multinucleated cells in GCTB and GCTTS, suggest a common cell lineage capable of multinucleated giant cell formation in the 3 tumors, despite differing histogenesis.

The Drosophila wing hearts consist of syncytial muscle cells that resemble adult somatic muscles

In Drosophila, hemolymph circulation in the wings is accomplished by a pair of wing hearts located in the thorax. The embryonic progenitors of these organs were only recently discovered and found to belong to the cardiac mesoderm. In this study, the functional morphology and the structure of mature organs were studied by light and electron microscopy to characterize the tissues arising from this new set of progenitors. Each wing heart consists of 7-8 muscle cells providing the pumping force, a thin layer of non-contractile mononucleated cells separating the muscle cells from the body cavity, and acellular suspending strands opposing the muscle contractions. The muscle cells are multinucleated syncytia attached to the cuticle via epidermal tendon cells. They have central nuclei and sarcomeres with discontinuous Z-discs, A-bands, and I-bands, whereas H-bands and M-bands are indiscernible. From 9 to 11 actin filaments surround each myosin filament. Mitochondria are abundantly interspersed between myofibrils and accumulated in characteristic outpockets of the plasma membrane. The analysis revealed that the wing heart muscles resemble in their ultrastructure and their mode of attachment adult somatic muscles. This suggests that, despite their origin in the cardiac mesoderm, wing heart progenitors are functionally related to somatic adult muscle precursors.

Immunohistochemical and transmission electron microscopy study regarding myofibroblasts in fibroinflammatory epulis and giant cell peripheral granuloma

Fibroblasts represent the main cellular population in the connective tissue; they have a central role in extracellular matrix (ECM) synthesis, degradation and remodeling. These cells may express a substantial heterogeneity regarding their morphology and functions in pathological conditions and during tissue remodeling. Myofibroblasts are a good example for heterogeneity and phenotypical changes. These cells can be morphologically and immunologically defined by the expression of specific cytoskeleton proteins. Myofibroblasts show cytoplasmic actin microfilaments organized as stress fibers and interconnected by gap or adherens junctions. These cells come also in contact with extracellular matrix by focal contacts. Myofibroblasts play fundamental roles in pathologic conditions, even by activation and proliferation or by deletion. Moreover, these cells seem to be involved in formation and repair of the ECM compounds, proliferation and differentiation of the epithelial, vascular or neurogenic elements. The purpose of the present study is to emphasize the presence and distribution of myofibroblasts in the reactive stromal tissue of granulation tumors in the oral area, fibroinflammatory epulis and giant cells peripheral granuloma, by means of immunocytochemical and transmission electron microscopy studies. Both tumor types shown a common characteristic of the presence of reactive inflammatory stromal tissue and myofibroblasts are a common issue.

A new gland associated with the retrocerebral complex of the adult corn earworm, Helicoverpa zea

We report the discovery of a single-celled putative new gland associated with the retrocerebral complex in the adults of Helicoverpa zea. The gland was not observed in Manduca sexta and few other species of moths. The pair of glands, each 50.6+/-5.5 microm in diameter, is located on either side of the recurrent nerve. Each gland is connected on one end through a fine nerve to the nervus corporis cardiaci-3 (NCC-3) and at the opposite end to the corpora allata through a thin fiber. The gland is composed of a giant cell with a large nucleus. The cytoplasm has an abundance of mitochondria in addition to dense bodies, electron lucent spheres, concentric whorls of rough endoplasmic reticulum and few vacuoles. At this stage we have no idea as to the function of this new gland.

MAP65-3 microtubule-associated protein is essential for nematode-induced giant cell ontogenesis in Arabidopsis

The infection of plants by obligate parasitic nematodes constitutes an interesting model for investigating plant cytoskeleton functions. Root knot nematodes have evolved the ability to manipulate host functions to their own advantage by redifferentiating root cells into multinucleate and hypertrophied feeding cells. These giant cells result from repeated rounds of karyokinesis without cell division. Detailed functional analyses demonstrated that Arabidopsis thaliana Microtubule-Associated Protein65-3 (MAP65-3) was essential for giant cell ontogenesis and that cytokinesis was initiated but not completed in giant cells. In developing giant cells, MAP65-3 was associated with a novel kind of cell plate-the giant cell mini cell plate-that separates daughter nuclei. In the absence of functional MAP65-3, giant cells developed but failed to fully differentiate and were eventually destroyed. These defects in giant cells impaired the maturation of nematode larvae. Thus, MAP65-3 is essential for giant cell development during root knot nematode infection. Subcellular localization of MAP65-3 and analysis of microtubule organization in the dyc283 T-DNA map65-3 mutant demonstrated that MAP65-3 played a critical role in organizing the mitotic microtubule array during both early and late mitosis in all plant organs. Here, we propose a model for the role of MAP65-3 in giant cell ontogenesis.

[Cytoplasmic syncytial connections between the cell bodies of the central nervous system neurons in adult animals]

The neurons of the gyrus dentatus, hippocampal area CA1-2, and the cerebellar granular cells were examined to test the hypothesis of the possibility of the syncytial connections between neuron cell bodies in the adult individuals of higher vertebrates. As a result of electron microscopic studies, the dense disposition of these neurons was shown together with their incomplete glial coverage. These cells were shown to establish the contacts with their cell membranes and to form interneuronal tight and gap membrane junctions. In these contact regions, the membrane perforations were found and the formation of cytoplasmic interneuronal syncytial connections with all their typical ultrastructural signs. Such connections could be established between several contacting neurons forming the common functional cellular cluster. These investigation confirm the hypothesis that the cytoplasmic syncytial interneuronal connections were possible, in addition to chemical synaptic and contact electrical connections, not only in the tissue culture and in the autonomic nervous system during the early postnatal ontogenesis, but also in CNS of the adult vertebrates.

Starch serves as carbohydrate storage in nematode-induced syncytia

The plant parasitic nematode Heterodera schachtii induces specific syncytial feeding sites in the roots of Arabidopsis thaliana from where it withdraws all required nutrients. Therefore, syncytia have to be well supplied with assimilates and generate strong sinks in the host plant's transport system. Import mechanisms and consequent accumulation of sucrose in syncytia were described recently. In this work, we studied the starch metabolism of syncytia. Using high-performance liquid chromatography and microscopic analyses, we demonstrated that syncytia store carbohydrates by starch accumulation. Further, we monitored the expression of genes involved in the starch metabolic pathway by gene chip analysis and quantitative reverse transcription-PCR. Finally, we provide functional proof of the importance of starch synthesis for nematode development using T-DNA insertion lines. We conclude that syncytia accumulate starch as a carbohydrate buffer to compensate for changing solute uptake by the nematode and as long-term storage during juvenile development.

Aflatoxin treatment brings about generation of multinucleate giant spermatids (symplasts) through opening of cytoplasmic bridges: Light and transmission electron microscopic study in Swiss mouse

Aflatoxins are dietary mycotoxins, which are a health hazard. Sub-symptomatic exposure to aflatoxins is known to produce male reproductive toxic effects with several manifestations. With a view to find if aflatoxins would produce multinucleate giant cells or symplasts in the seminiferous epithelium, we treated male Swiss mice with aflatoxin B(1) for 35 days and subjected the testis to light and transmission electron microscopic analysis. We found abundant symplastic spermatids in the seminiferous epithelium of treated mice. The origin of these cells was traced to opening of cytoplamic bridges. Due to widening of cytoplasmic bridge, the cytoplasm of spermatid(s) in a clone entered a cytoplasm-rich spermatid, followed by the nucleus/nuclei. Subsequently, the bridge(s) collapsed resulting in spherical symplasts. The study, in addition to revealing yet another manifestation of aflatoxin-induced disruption of spermatogenesis, also provides first direct evidence for opening of cytoplasmic bridges as the mechanism underlying origin of spermatid symplasts.

Role of the cytoplasmic tail domains of Bunyamwera orthobunyavirus glycoproteins Gn and Gc in virus assembly and morphogenesis

The M RNA genome segment of Bunyamwera virus (BUNV), the prototype of the Bunyaviridae family, encodes a precursor polyprotein that is proteolytically cleaved to yield two structural proteins, Gn and Gc, and a nonstructural protein called NSm. Gn and Gc are type I integral transmembrane glycoproteins. The Gn protein contains a predicted cytoplasmic tail (CT) of 78 residues, and Gc has a shorter CT of 25 residues. Little is known about the role of the Gn and Gc CT domains in the virus replication cycle. We generated a series of mutant glycoprotein precursor constructs containing either deletions or alanine substitutions in the CT domains of Gn and Gc. We examined the effects of these mutations on glycoprotein maturation, cell surface expression, and low pH-induced syncytium formation. In addition, the effects of these mutations were also assessed using a reverse genetics-based virus assembly assay and a virus rescue system. Our results show that the CT domains of both Gn and Gc play crucial roles in BUNV-mediated membrane fusion, virus assembly, and morphogenesis.

Multinucleated stromal giant cells in colonic lamina propria

AIMS

Multinucleated stromal giant cells occur in the anus, genitals and many other organs. They resemble myofibroblasts, react to local injury and are found incidentally or in association with various lesions. They have only rarely been reported to occur in the colon. The aim was to firmly establish their existence in colorectal lamina propria.

METHODS AND RESULTS

Specimens from one hundred biopsies taken from throughout the colon (70%) and rectum (30%) were retrospectively reviewed. Multinucleated stromal giant cells occurred in 23 specimens (23%), were pancolonic but surprisingly spared rectal mucosa (0%). Multinucleated stromal giant cells occurred in both normal mucosa and abnormal mucosa and appeared to be larger and more numerous in abnormal mucosa than in normal mucosa. Specimens with tubular adenomas appeared to have strikingly abundant multinucleated stromal giant cells with large numbers of nuclei. Immunohistochemistry and ultrastructural examination showed features consistent with myofibroblastic differentiation.

CONCLUSIONS

We have firmly established the existence of multinucleated stromal giant cells in colonic lamina propria and confirm their myofibroblastic differentiation. They may be more common in abnormal mucosa and particularly prominent in the setting of tubular adenoma. Absence of rectal multinucleated stromal giant cells may represent a microanatomical difference between the colon and rectum.

Langhans giant cells from M. tuberculosis-induced human granulomas cannot mediate mycobacterial uptake

Tuberculosis is characterized by a tight interplay between Mycobacterium tuberculosis (M. tb) and host cells within granulomas. These cellular aggregates restrain M. tb spreading but do not kill all bacilli, which persist for years. A more detailed investigation of the interaction between M. tb and granuloma cells is needed to improve our understanding of this persistence and to explain the physiopathology of tuberculosis. In the present study, a recently developed in vitro human model of tuberculous granulomas has been used to analyse the modulation of granuloma cell differentiation by M. tb, in comparison to poorly virulent mycobacteria, which do not persist. It is reported that whilst all mycobacteria species induce granuloma formation, only M. tb triggers the differentiation of granuloma macrophages into very large multinucleated giant cells (MGCs) that are unable to mediate any bacterial uptake. This loss of function is not due to cell quiescence, as MGCs still display NADPH oxidase activity, but it correlates with decreased expression of phagocytosis receptors. This phenomenon is specific for the virulent species of M. tuberculosis complex, as poorly virulent species only induce the formation of small multinucleated cells (MCs) with conserved mycobacterial uptake ability, which never reach the MGC differentiation stage. The phenotype of MGCs thus strongly resembles mature dendritic cells with a loss of microbial uptake ability, despite conserved antigen presentation. In M. tb-induced granulomas, MGCs thus seem to be devoted to the destruction of bacilli that have been ingested in previous differentiation stages, ie in macrophages and MCs.

Interconnected Network of Ganglion-Like Neural Cell Spheres Formed on Hydrozoan Skeleton

Identifying scaffolds supporting in vitro reconstruction of active neuronal tissues in their 3-dimensional (3D) conformation is a major challenge in tissue engineering. We have previously shown that aragonite coral exoskeletons support the development of neuronal tissue from hippocampal neurons and astrocytes. Here we show for the first time that the porous aragonite skeleton obtained from bio-fabricated hydrozoan Millepora dichotoma supports the spontaneous organization of dissociated hippocampal cells into highly interconnected 3D ganglion-like tissue formations. The ganglion-like cell spheres expanded hundreds of microns across and included hundreds to thousands of astrocytes and mature neurons, most of them having only cell-cell and no cell-surface interactions. The spheres were linked to the surface directly or through a neck of cells and were interconnected through thick bundles of dendrites, varicosity-bearing axons, and astrocytic processes. Thus, M. dichotoma exoskeleton is a novel scaffold with the unprecedented ability to support a highly ordered organization of neuronal tissue. This unexpected organization opens new opportunities for neuronal tissue regeneration, because the spheres resemble in vivo nervous tissue having high volume of cells associated primarily through cell-cell rather than cell-matrix interactions.

Blown fuse regulates stretching and outgrowth but not myoblast fusion of the circular visceral muscles in Drosophila

Circular visceral muscles of Drosophila are binuclear syncytia arising from fusion of two different kinds of myoblasts: a circular visceral founder cell and one visceral fusion-competent myoblast. In contrast to fusion leading to the somatic body-wall musculature, myoblast fusion for the circular visceral muscles does not result in massive syncytia but instead in syncytia interconnected with multiple cytoplasmic bridges, which differentiate into large web-shaped muscles. Here, we show that these syncytial circular visceral muscles build a gut-enclosing network with the interwoven longitudinal visceral muscles. At the ultrastructural level, during circular visceral myoblast fusion and the first step of somatic myoblast fusion prefusion complexes and electron-dense plaques were not detectable which was surprising as these structures are characteristic for the second step of somatic myoblast fusion. Moreover, we demonstrate that Blown fuse (Blow), a cytoplasmic protein essential for the second step of somatic myoblast fusion, plays a different role in circular visceral myogenesis. Blow is known to be essential for progression beyond the prefusion complex in the somatic mesoderm; however, analysis of blow mutants established that it has a restricted role in stretching and outgrowth of the syncytia in the circular visceral muscles. Furthermore, we also found that in the visceral mesoderm, Blow is expressed in both the fusion-competent myoblasts and circular visceral founders, while expression in the somatic mesoderm is initially restricted to fusion-competent myoblasts. We also demonstrate that different enhancer elements in the first intron of blow are responsible for this distinct expression pattern. Thus, we propose a model for Blow in which this protein is involved in at least two clearly differing processes during Drosophila muscle formation, namely somatic myoblast fusion on the one hand and stretching and outgrowth of circular visceral muscles on the other.

Carboxypeptidase E in the mouse placenta

Carboxypeptidase E (CPE) has important functions in processing of endocrine pro-peptides, such as pro-insulin, pro-opiomelanocortin, or pro-gonadotropin-releasing hormone, as evidenced by the hyper-pro-insulinemia, obesity, and sterility of Cpe mutant mice. Down-regulation of Cpe in enlarged placentas of interspecific hybrid (interspecies hybrid placental dysplasia (IHPD)) and cloned mice suggested that reduced CPE enzyme and receptor activity could underlie abnormal placental phenotypes. In this study, we have explored the role of Cpe in murine placentation by determining its expression at various stages of gestation, and by phenotypic analysis of Cpe mutant placentas. Our results show that Cpe and Carboxypeptidase D (Cpd), another carboxypeptidase with a very similar function, are strictly co-localized in the mouse placenta from late mid-gestation to term. We also show that absence of CPE causes a sporadic but striking placental phenotype characterized by an increase in giant and glycogen cell numbers and giant cell hypertrophy. Microarray-based transcriptional profiling of Cpe mutant placentas identified only a very small number of genes with altered expression, including Dtprp, which belongs to the prolactin gene family. Concordant deregulation of Cpe and Cpd in abnormal placentas of interspecies hybrids before the onset of IHPD phenotype and recapitulation of some phenotypes of IHPD hyperplastic placentas in Cpe mutant placentas suggests that these two genes are causally involved in IHPD and may function as speciation genes in the genus Mus.

Mycobacterial Lipomannan Induces Granuloma Macrophage Fusion via a TLR2-Dependent, ADAM9- and β1Integrin-Mediated Pathway

Tuberculous granulomas are the sites of interaction between the host response and the tubercle bacilli within infected individuals. They mainly consist of organized aggregations of lymphocytes and macrophages (Mf). A predominant role of mycobacterial envelope glycolipids in granulomas formation has been recently emphasized, yet the signaling events interfering with granuloma cell differentiation remain elusive. To decipher this molecular machinery, we have recently developed an in vitro human model of mycobacterial granulomas. In this study, we provide evidence that the mycobacterial proinflammatory phosphatidyl-myo-inositol mannosides and lipomannans (LM), as well as the anti-inflammatory lipoarabinomannan induce granuloma formation, yet only the proinflammatory glycolipids induce the fusion of granuloma Mf into multinucleated giant cells (MGC). We also demonstrate that LM induces large MGC resembling those found in vivo within the granulomas of tuberculosis patients, and that this process is mediated by TLR2 and is dependent on the beta(1) integrin/ADAM9 cell fusion machinery. Our results demonstrate for the first time that the Mf differentiation stage specifically occurring within granulomatous structures (i.e., MGC formation) is triggered by mycobacterial envelope glycolipids, which are capable of inducing the cell fusion machinery. This provides the first characterization of the ontogeny of human granuloma MGC, thus resulting in a direct modulation by a particular mycobacterial envelope glycolipid of the differentiation process of granuloma Mf.

In vivo response to starch‐based scaffolds designed for bone tissue engineering applications

Our purpose was to evaluate the in vivo endosseous response to three starch-based scaffolds implanted in rats (n = 54). We implanted the three scaffold groups; a 50/50 (wt %) blend of corn starch and ethylene-vinyl alcohol (SEVA-C), the same composition coated with a biomimetic calcium phosphate (Ca-P) layer (SEVA-C/CaP), and a 50/50 (wt %) blend of corn starch and cellulose acetate (SCA), all produced by extrusion with blowing agents, into distal femurs proximal to the epiphyseal plate, for 1, 3, or 6 weeks. Our results showed that at 1 week considerable reparative bone formed around all scaffold groups, although the bone was separated from the scaffold by an intervening soft tissue interfacial zone that comprised two distinct compartments: the surface of the scaffold was occupied by multinucleate giant cells and the compartment between these cells and the surrounding bone was occupied by a streaming fibrous-like tissue. The extracellular matrix of the latter was continuous with the extracellular bone matrix itself, labeled positively for osteocalcin and appeared mineralized by back-scattered electron imaging. All three scaffolds showed a similar tissue response, with the soft tissue interface diminishing with time. No bone contact was observed with SEVA-C at any time point, only transitory bone contact was observed with SEVA-C/CaP at 3 weeks, but SCA exhibited direct bone contact at 6 weeks where 56.23 +/- 6.46% of the scaffold surface was occupied by bone. We conclude that all materials exhibited a favorable bony response and that the rapidly forming initial "connective tissue" seen around all scaffolds was a very early form of bone formation.

Primary biliary cirrhosis with multinucleated hepatocellular giant cells: implications for pathogenesis of primary biliary cirrhosis

Histological and clinical features of syncytial giant cell hepatitis (GCH) are rarely observed in adults, and the disease has been associated with several autoimmune disorders and drug reactions. We describe here the case of a 62-year-old woman who presented with evidence of severe acute hepatocellular injury and cholestasis. Serum work-up demonstrated antimitochondrial antibodies specific for primary biliary cirrhosis (PBC) autoantigens, whereas markers of viral infection including hepatitis viruses, paramyxovirus and measles virus were negative. Liver histology revealed the presence of multinucleated hepatocellular giant cells in the parenchymal areas surrounding bridging necrosis. Importantly, damaged interlobular bile ducts were also observed within the lymphocyte-infiltrated portal tracts. Further study using transmission electron microscopy demonstrated the presence of filamentous strands and particles resembling paramyxovirus nucleocapsids in the cytoplasm of syncytial giant cells. To our knowledge, this is the first case of PBC with histological and clinical evidence of syncytial GCH in an adult, and we submit that it might provide novel clues in the enigma of PBC pathogenesis.

Mitotic polyploidization in trophoblast giant cells of the alpaca

Genome multiplication is a typical feature of trophoblast giant cell (TGC) development in many species. Elevated nuclear DNA contents can be achieved by modified cell cycles with a complete lack of mitosis (endoreduplication) or with incomplete mitoses. The aim of this study is to characterize genome multiplication in the alpaca TGC. Placental tissues of gestation days 150, 264 and 347 (near term) and term placentae were processed for light microscopy and for transmission electron microscopy. Each TGC showed many nuclear profiles. Observation of serial sections revealed that TGCs are truly multinucleate with several highly lobulated nuclei. Feulgen staining showed that TGC nuclei have a higher DNA content than nuclei of other trophoblast cells. The number of argyrophilic nucleolar organizer regions (AgNORs) in nuclear profiles of TGC was between 15 and 100, while other trophoblast cells showed 1 or 2 AgNORs. Large multipolar mitotic figures with maximal diameters of 80 mum were observed in the alpaca placentas on gestation days 264 and 347. No cytokinesis was seen in TGC. The results show that the mode of genome multiplication in the alpaca TGC is mitotic polyploidization. Subsequent acytokinetic mitoses may lead to an accumulation of chromosomes and centrioles in TGC. With increasing ploidy levels, the shape of these polyploidizing mitoses becomes more irregular. The restitution of nuclei after these complex multipolar mitoses is likely to result in the irregular nuclear shape in TGC.

The secretory membrane system in the Drosophila syncytial blastoderm embryo exists as functionally compartmentalized units around individual nuclei

Drosophila melanogaster embryogenesis begins with 13 nuclear division cycles within a syncytium. This produces >6,000 nuclei that, during the next division cycle, become encased in plasma membrane in the process known as cellularization. In this study, we investigate how the secretory membrane system becomes equally apportioned among the thousands of syncytial nuclei in preparation for cellularization. Upon nuclear arrival at the cortex, the endoplasmic reticulum (ER) and Golgi were found to segregate among nuclei, with each nucleus becoming surrounded by a single ER/Golgi membrane system separate from adjacent ones. The nuclear-associated units of ER and Golgi across the syncytial blastoderm produced secretory products that were delivered to the plasma membrane in a spatially restricted fashion across the embryo. This occurred in the absence of plasma membrane boundaries between nuclei and was dependent on centrosome-derived microtubules. The emergence of secretory membranes that compartmentalized around individual nuclei in the syncytial blastoderm is likely to ensure that secretory organelles are equivalently partitioned among nuclei at cellularization and could play an important role in the establishment of localized gene and protein expression patterns within the early embryo.

Immunohistochemical and microscopic studies on giant cells in tuberous sclerosis

Tuberous sclerosis (TSC) is an autosomal dominant disease, caused by mutations in TSC1 or TSC2 genes, encoding hamartin and tuberin, respectively. The clinical picture of the disease is connected with the formation of hamartomas, mainly in the heart, kidneys and the brain. In three types of brain lesions: cortical tubers, subependymal nodules and subependymal giant-cell astrocytoma (SEGA) characteristic, so-called "giant cells" are found. In the present review we summarise immunohistochemical findings of two types of studies performed on giant cells aiming at establishing the expression of hamartin and tuberin level and determining the presence of neuron- or astrocyte-specific markers. Moreover, we support our argument with the summary of ultrastructural research done with the purpose of demonstrating structures characteristic of neural and/or glial cells. We conclude that giant cells in cortical tubers and SEGAs are the same undifferentiated cells that, depending on individual determination, can show neural or glial features.

Ultrastructural Characterization of Tissue Response to Sintered Carbonate Apatite in Rabbit Bone

Our previous in vivo and in vitro studies revealed excellent tissue biocompatibility and osteoconductivity of porous sintered carbonate apatite (CA). The present study focused on the ultrastructural details of cells involved in the degradation of CA and new bone formation. Electron microscopy indicated that multinucleated giant cells (MNGCs) were actively involved in CA resorption. MNGCs extended their irregular cytoplasmic protrusions deeply into the interstitial spaces between CA particles. Endophagosomes were formed by encircling partially dissolved or intact CA crystals via the development of pseudopodia-like cytoplasmic protrusions, the configuration of which was somewhat different from that of the typical ruffled border of bone-resorbing osteoclasts. Subsequently, most CA particles in MNGCs were irregular in shape, suggesting that acidic degradation of CA occurred mainly intracellularly. Mononuclear cells, such as macrophage-like and/or fibroblast-like cells, also took up and degraded some CA. Growth of very thin needle-like crystals was observed in close association with CA. Osteoblasts directly faced the CA and secreted osteoid matrix. At the CA-bone interface, an electron-dense and homogeneous thin layer free of collagen fibers was sometimes observed, suggesting an involvement in CA-bone bonding.

Quantitative histological and ultrastructural features of opercula of normally erupting human teeth

Tooth eruption across the mucosa in humans has been studied rarely, although there are disturbances of eruption that are attributed specifically to failure of the supraosseous eruptive migration. The aim of this study was to analyze the soft tissues covering normally erupting teeth so as to get an insight into the supraosseous phase of tooth eruption and to provide the basis for comparison with cases of eruption disturbances. Six opercula covering normally erupting permanent molars (primary opercula) and six of succedaneous teeth (secondary opercula) were surgically removed from 10 patients aged 7.5-17.5 years. Specimens were examined light and electron microscopically and analyzed morphometrically. All opercula contained strands and islands of odontogenic epithelium, prominent numbers of high endothelial venules, nerves, and mast cells. Nerves comprised normally structured, 1.5-3.5 microm thick myelinated (Adelta) and thinner unmyelinated (C) fibers. In primary opercula, the proportions of blood vessels and nerves were three- and sevenfold higher than the respective values for the secondary opercula. Furthermore, primary opercula contained multinucleated, fibroblast-like giant cells that were not observed in secondary opercula. As all teeth under investigation were erupting normally, neither the presence of the giant cells nor the atypical proportions of blood vessels and nerves appeared to be decisive in the eruption process. These conspicuous tissue components of opercula seem merely to accompany the eruptive tooth movement.

Whole-genome chromosome distribution during nuclear fragmentation of giant trophoblast cells of Microtus rossiaemeridionalis studied with the use of gonosomal chromatin arrangement

Gonosomal chromatin bodies (GCBs), i.e. blocks of condensed chromatin consisting of heterochromatized region of the sex chromosomes of the field vole M. rossiaemeridionalis, were used as a natural interphase chromosome marker in order to clarify the regularities of GCB rearrangement during nuclear fragmentation of secondary giant trophoblast cells (SGTCs) at the end of their differentiation. Cytophotometrical measurements of DNA content in the nuclei, nuclear fragments and simultaneously in the GCBs were made in the secondary giant SGTCs of field vole M. rossiaemeridionalis. In most cases 1 to 2 GCBs get into the nuclear fragments at different ploidy levels. In the nuclear fragments, GCB DNA content decreased mostly proportionally to DNA content in the whole fragments corresponding to 2c, 4c and 8c. The data obtained demonstrate a regular whole-genome chromosome distribution into nuclear fragments. A possible mechanism of nuclear fragmentation that largely ensures a balanced genome in nuclear fragments is discussed.

Multinucleated giant cell formation exhibits features of phagocytosis with participation of the endoplasmic reticulum

Macrophage fusion leading to formation of multinucleated giant cells during chronic inflammation is poorly understood in mechanism and physiological significance. To address this, we developed a system of human macrophage fusion that utilizes IL-4, IL-13, or alpha-tocopherol to generate large foreign body-type giant cells (FBGC). Extending our previously demonstrated requirements for F-actin and mannose receptor (MR) activity, we find that macrophage fusion exhibits further features of a phagocytic process. Pharmacological inhibition of IL-4-induced FBGC formation indicates critical roles for vacuolar-type ATPase, microtubules, the endoplasmic reticulum (ER), and calcium-independent phospholipase A(2) (iPLA(2)), but not calcium-dependent PLA(2) (cPLA(2)), secretory PLA(2) (sPLA(2)), cyclooxygenase, or lipoxygenase. Immunocytochemistry confirms iPLA(2) expression and absence of cPLA(2) or sPLA(2) expression in macrophages/FBGC. As markers of ER-mediated phagocytosis, calnexin and calregulin are detectable on non-permeabilized fusing macrophages and also concentrated at fusion interfaces where they co-localize with actin in permeabilized macrophages/FBGC. Furthermore, ER markers co-localize with concanavalin A reactivity on non-permeabilized fusing macrophages, suggesting that the ER may present MR ligand during fusion events. These data demonstrate for the first time that the mechanism of macrophage fusion leading to formation of multinucleated giant cells exhibits multiple features of phagocytosis with potential participation of the ER.