Heat shock activation of telomeric sequences in different tissues of Chironomus thummi

The authors present ultrastructural and immunohistochemical characteristics of an intracranial suprasellar tumor displaying features of cavernous angioma with islets of adipose tissue. Electron microscopy revealed thin-walled vessels separated by a loose collagenous stroma containing nests of mature adipocytes as well as fibroblasts, myofibroblasts, mast cells, and a few macrophages. Intracytoplasmic lipid droplets were also identified in scattered pericytes and smooth muscle cells of vascular walls and in the transitional cells resembling smooth muscle cells and adipocytes. Many adipose tissue cells were positive for S-100 protein with polyclonal antibodies. Other lipidized tumor cells were immunoreactive for some or all of the following: smooth muscle-specific actin, factor XIIIa, vimentin, and, occasionally, for desmin. Ultrastructure and immunohistochemistry indicate that in addition to typical adipocytes, lipidized cells of another nature contribute to the characteristic appearance of the adipose tissue component of angiolipoma.     

The ultrastructural examination of gingival fibromatosis

Hereditary gingival fibromatosis (GF) is a special type of fibrous overgrowth classified as non-inflammatory gingival enlargement. Microscopically, the connective tissue consists of coarse collagen bundles and fibroblasts. The ultrastructural examination of fibrous gingival hyperplasia reveals that fibroblasts phagocyte the mast cell granules and mast cells stimulate collagen synthesis which results in hyperplasia. In the ultrastructural examination of phenytoin-induced hyperplasia, fibroblasts, phagocytosing mast cell granules were also found. Based on these findings, the purpose of this study is to establish whether there is a relationship between fibroblasts and mast cells in GF. The gingival tissues of 5 patients with GF were examined ultrastructurally. In the connective tissue, well-defined bundles of collagen fibres were found together with fibroblasts and capillaries. There were mast cells around these capillaries which had collapsed lumens. The proximity of the mast cells and fibroblasts may indicate that mast cells play some role on collagen synthesis of fibroblasts.     

Ultrastructural and immunohistochemical studies of Wharton's jelly umbilical cord cells

In order to determine the significance of Wharton's jelly, the characteristics of these cells were examined by means of electron microscopy and immunohistochemistry. These cells possessed ultrastructural characteristics of both fibroblasts and smooth muscle cells, indicating that they are modified, rather than typical fibroblasts. Immunohistochemically those 'myofibroblasts' stained positive for actin, non-muscle myosin, vimentin and desmin. Staining for muscle myosin was negative, supporting the ultrastructural findings. As our results indicate that these cells can function in both fibrogenesis and cell contraction, we speculate that they may contribute to the elasticity of Wharton's jelly, by synthesizing collagen fibers, and participate in the regulation of umbilical blood flow by virtue of their contractile properties.     

An ultrastructural study of the intimal hyperplasia in healing microarterial anastomoses

The purpose of the study was to investigate the ultrastructure of intimal hyperplastic cells. End-to-end microarterial anastomoses were studied in a rabbit free-tissue-transfer model. There were five experimental groups, with 1, 3, 7, 14, or 28 days follow-up. At sacrifice the anastomoses were tested for patency and then examined by light and electron microscopy. At days 1 and 3 the repaired intima was covered with macrophages and extravasated erythrocytes. At day 7 spindle-shaped fibroblasts with copious rough endoplasmic reticulum were seen. Some of these cells also contained pinocytotic vesicles, filaments with focal densities, and subplasmalemmal attachment sites, the features of smooth muscle cells. At day 14, more cells contained smooth muscle features and these features were also more pronounced. These young myofibroblasts were plumper than adjacent fibroblasts. At day 28 mature myofibroblasts with a full complement of organelles were present. The results, therefore, supported the hypothesis that myofibroblasts are present in the intimal hyperplasia of healing microarterial anastomoses.     

Ultrastructure of infantile hemangioendothelioma of the liver

A two-month-old female presented with hepatomegaly 5 cm below the right costal margin. Resection of a 6 cm hepatic mass demonstrated an infantile hemangioendotheliom (IHE). This documents for the first time the ultrastructural features of an IHE of the liver. Ultrastructural examination showed large numbers of vascular channels of varying sizes lined by abnormal endothelial cells. An incomplete basal lamina separated the endothelial cells from the extracellular material and there were no associated pericytes. The intervascular area contained abundant collagen fibers, fibrils, and cells ultrastructurally similar to fibroblasts. The relationship of structure to certain clinical features of this lesion is discussed.     

Effects of honey consumption on enamel microhardness in normal versus xerostomic patients

BACKGROUND: This report describes the pathology of a myolipoma which occurred in the eyelid. Myolipoma is a benign hamartomatous tumour in which smooth muscle cells are interspersed with adipocytes. PATIENT DETAILS: An irregular yellowish tumour (30 x 25 mm) with illdefined borders had been present for 50 years in the medial part of the left lower eyelid of a 67-year-old woman. The tumour was excised and studied by conventional histology, immunohistochemistry and transmission electron microscopy. RESULTS: The tumour was formed by bundles of spindle-shaped cells with cigarshaped nuclei intermingled with multiloculated clear cells containing small eccentric nuclei. By immunohistochemistry, positive staining of the spindle cells was restricted to smooth muscle actin and desmin; the clear cells were non-reactive with the immunohistochemical panel, but fat was identified within the cytoplasm. The ultrastructural features of the spindle cells were those of a leiomyoma, while the clear cells were classified as adipocytes. CONCLUSION: This tumour was considered to originate from the media of blood vessels within the tumour.     

Ultrastructure of gastric myxofibroma with intracytoplasmic collagen

Electron microscopy of a small mass removed from the stomach of a 65-year-old women demonstrated a myxofibroma composed of a pure population of fibroblasts, many of which contained intracytoplasmic, membrane-bound collagen fibers similar to those found in a few other human tumors and in certain experimental conditions. This ultrastructural documentation supports the hypothesis that pure fibrous neoplasms of the stomach do occur. Electron microscopy of gastric mesenchymal tumors almost always allows for confident differentiation among fibrous, neural, and smooth muscle neoplasms.     

Quantification of exercise-induced pulmonary haemorrhage with bronchoalveolar lavage

Primary liposarcoma of the stomach is rare and only seven cases have been described in the English literature. Here we report the eighth case, which occurred in a 68-year-old woman who presented with repeated tarry stools and hematemesis. Endoscopic examination revealed a large ulcerated submucosal mass at the gastric angle. The patient was treated by total gastrectomy. On microscopic examination, the tumor showed the features of a well differentiated sclerosing liposarcoma. Immunohistochemically, many spindle to stellate tumor cells were diffusely positive for vimentin and CD34. Positivity for S-100 protein was found in the adipocytic component, including lipoblasts, in addition to some spindle-shaped tumor cells. On ultrastructural examination, the spindle to stellate cells had features characteristic of fibroblasts. No recurrence or metastasis was seen during 13 months. Liposarcoma of the stomach has to be considered in the differential diagnosis with other submucosal lesions, such as gastric lipoma and gastrointestinal stromal tumor.     

Clear cell tumor of the lung: an immunohistochemical and ultrastructural study supporting a pericytic differentiation

Clear cell tumor ("sugar tumor") of the lung is a rare benign lesion with unclear histogenesis. It is composed of large cells with a clear cytoplasm rich in glycogen, blended with an abundant network of sinusoid-type vessels. We report two cases of sugar tumor, one of these lacking clearly demonstrable glycogen storage. In both, the tumor cells lacked keratin expression and were positive for vimentin and HMB 45, an antibody recognizing perivascular or myoid cell proliferation such as lymphangioleiomyomatosis and angiomyolipoma. The tumor cells were also immunoreactive for an endothelial cell marker, CD 34, but negative for Factor VIII or smooth muscle actin. Intercellular deposition of basal-like material was immunostained with Type IV collagen. At ultrastructural examination of one of these cases, tumor cells showing features of pericytes or poorly differentiated perivascular leiomyocytes encased in basement material were observed in close association with endothelial cells; their cytoplasm contained numerous membrane-bound glycogen and pinocytic vesicles. We conclude that on the basis of immunohistochemical and ultrastructural phenotype, sugar tumor presents pericytic features and that glycogen storage is not a constant feature of these benign tumors.     

Identification of epithelial cells and fibroblasts in hypophysis intermediate lobe cultures by scanning electron microscopy

Cell cultures of the rat pituitary intermediate lobe grown for eight days were studied in the scanning electron microscope. The epithelial cells and fibroblasts could be differentiated by the characteristic structures of the cell surface and the cell association features, The epithelial cells were characterized by blebs and rugae, microvilli, and occasionally by some cilia. The surface of the fibroblasts was smooth or bore microvilli. Scanning electron microscopy may provide special information for the characterization of endocrine cell cultures.     

Autoxidation of pyridoxalated hemoglobin polyoxyethylene conjugate

Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen which stimulates angiogenesis. VEGF is regulated by multiple factors such as hypoxia, phorbol esters, and growth factors. However, data concerning the expression of VEGF in the different vascular cell types and its regulation by cAMP are not available. In the present study, we have investigated the effect of adenylate cyclase activation on VEGF mRNA expression in rat vascular cells in primary culture. Basal VEGF expression is greater in smooth muscle cells than in endothelial cells and fibroblasts. A 4-h treatment with forskolin (10(-5) M) induced a 2-fold stimulation of VEGF mRNA expression in smooth muscle cells and fibroblasts, but, in contrast, did not affect VEGF expression in endothelial cells. In smooth muscle cells, a pharmacologically induced increase in intracellular cAMP levels using iloprost or isoprenaline led to a rise in VEGF mRNA expression comparable to that induced by forskolin. Adenosine, which increases cAMP levels in smooth muscle cells, also increases VEGF expression. Moreover, the 2.2-fold stimulation of VEGF expression by adenosine was enhanced following a cotreatment with cobalt chloride (a hypoxia miming agent). The observed additive effect (4.3-fold increase) suggests that these two factors, hypoxia and adenosine, regulate VEGF mRNA expression in smooth muscle cells by independent mechanisms.     

Ultrastructural characteristics of fibroblasts, myofibroblasts, and fibroclasts in the process of wound healing (author's transl)

5 types of fibroblasts were characterized by histomorphometrical and ultrastructural examinations of the wound healing of rats, 3, 7, 14 and 21 days p. op. These cells were undifferentiated mesenchymal cells, immature fibroblasts, mature fibroblasts, myofibroblasts and fibroclasts. The functions of these cells were discussed with respect to cell proliferation, synthesis, and degradation of collagen.     

Interfollicular fibroblasts in the human thyroid gland: recognition of a CD34 positive stromal cell network communicated by gap junctions and terminated by autonomic nerve endings

While epithelial structure and functions have been substantially investigated in many organs, the mesenchymal elements have received less attention. Compared with follicular epithelial cells, there are a few morphological studies on the stroma of human thyroid gland. In order to characterize more fully and assess its possible functions, 15 samples of surgical and autopsy human thyroid tissue were studied by classical histology, immunohistochemistry, transmission electron microscopy, electron microscopic immunohistochemistry, and scanning electron microscopy. In human thyroid gland, the interfollicular connective tissue surrounding the follicles contained collagenous matrix, fibroblasts, unmyelinated nerve fibers with Schwann cells, small blood vessels, lymphatics, lymphocytes, plasma cells, macrophages, and mast cells. At the ultrastructural level, gap junctions between the cytoplasmic processes of interfollicular fibroblasts constituted a novel observation. Immunohistochemistry using a monoclonal antibody against Cx43 confirmed the distribution of gap junctions between stromal fibroblastic cells, which was compatible with the ultrastructural findings. The frequent and intimate association of fibroblastic processes with nerve terminals was also shown. Interfollicular stromal fibroblasts also stained with CD34. The main constituent of the human thyroid stromal tissue was a CD34 positive reticular network involving fibroblasts, mononuclear cells and nerve terminals. It represents a highly ordered stroma, with potential structural and functional similarities to the stroma of bone marrow (Yamazaki and Allen, 1990).     

FGF-10 is a chemotactic factor for distal epithelial buds during lung development

BACKGROUND: We investigated the ability of a variety of growth factors to regulate the differentiation of prostatic fibroblasts into smooth muscle cells. METHODS: Smooth muscle actin levels were monitored by immunoblot analysis and immunocytochemistry. Proliferation was measured in clonal growth assays and by cell counts. RESULTS: We determined that TGFbeta inhibited proliferation and induced smooth muscle differentiation of stromal cells derived from prostatic adenocarcinomas, as we previously reported for cells derived from the normal peripheral zone. Basic FGF, EGF, TGFalpha, and PDGF, but not IGF, retinoic acid, 1,25-dihydroxyvitamin D3, or androgen, attenuated induction of differentiation by TGFbeta, by a mechanism apparently unrelated to proliferation. CONCLUSIONS: Regulation of growth and differentiation occurs equivalently in prostatic stromal cells derived from adenocarcinomas and normal peripheral zone. TGFbeta is a potent inducer of the smooth muscle phenotype. Basic FGF, EGF and/or TGFalpha, and PDGF attenuate TGFbeta's activity, and promote a fibroblastic phenotype. Our studies provide an in vitro model system in which fibroblastic or smooth muscle cells can be promoted, maintained, and investigated in a defined manner. The results suggest that the ratio of fibroblasts to smooth muscle cells in the stroma reflects the relative levels of growth factors, which may be altered in diseased states.     

Contractile events during inflammation

Contractile events during wound healing. During granulation tissue contraction, fibroblasts develop characteristics typical of smooth muscle; (1) they contain an extensive cytoplasmic fibrillar system, (2) they show immunofluorescent labeling of anti-actin antibodies, (3) there are cell and cell to stroma attachments, (4) strips of granulation tissue, when tested pharmacologically in vitro, behave similarly to smooth muscle. These data support the view that under certain conditions, fibroblasts can differentiate into a cell type structurally and functionally similar to smooth muscle and this cell, the 'myofibroblast', plays an important role in connective tissue contraction. During epithelialization, epidermal cells develop an extensive cytoplasmic contractile apparatus which has morphological and immunological characteristics similar to those of myofibroblasts. Such apparatus disappears as soon as epithelialization is completed. It is proposed that such a contractile apparatus plays a role in cell motility enabeling individual cells to rearrange themselves in an appropriate pattern. In conclusion, significant amounts of contractile proteins may be synthetized by fibroblasts and epithelial cells during wound healing and may play an important role in this process.     

Smooth muscle cell to elastic lamina connections in developing mouse aorta. Role in aortic medial organization

BACKGROUND: The structural and functional intigration of smooth muscle cells and elastic laminae in the aortic media is not well established. Detailed information concerning normal ultrastructural features of the aortic media will provide a better understanding of the medial changes that occur in vascular diseases such as hypertension and aortic aneurysms. EXPERIMENTAL DESIGN: The ultrastructural development and organization of connections between smooth muscle cells and elastic laminae in the mouse aortic media were studied by light and electron microscopy. RESULTS: Early in development, the smooth muscle cells become linked to the elastic laminae by bundles of microfibrils. These microfibrils become progressively infiltrated with elastin so as to form extensions of elastin from the elastic laminae in the adult media. Each elastin extension spans obliquely from the elastic lamina to the surface of the smooth muscle cell where it attaches in a region of membrane occupied by an intracellular membrane-associated dense plaque. On the cytoplasmic face of the plaque, a contractile filament bundle penetrates and anchors in an orientation similar to that of the extracellular elastin extension. The contractile filament bundle traverses the cell obliquely and anchors in a dense plaque on the opposite side of the cell that is in turn linked to the next elastic lamina by another elastin extension. The extracellular elastin extensions and the intracellular contractile filament bundles thus form a "contractile-elastic unit," a continuous line of structures that links adjacent elastic laminae. The oblique orientation of the contractile-elastic units reverses direction in successive smooth muscle cell layers in a herringbone-like pattern. Thus, tension transmitted to one elastic lamina by the smooth muscle cells on either side results in a uniform force exerted on the elastic lamina in one circumferential direction, that on the adjacent elastic laminae being in the opposite direction. CONCLUSIONS: Results from this study demonstrate the presence of smooth muscle cell to elastic lamina connections that form early in development as contractile-elastic units; basic units of aortic medial ultrastructure. The overall organization of the contractile-elastic units within the aortic media is proposed to provide a means for coordinating contractile and elastic tensions in response to mechanical stresses imposed on the vessel wall.     

Technical note: Modeling primate occlusal topography using geographic information systems technology

We studied the effects of FGF-13 and FGF-2 on human lung fibroblasts, dermal microvascular endothelial cells, and aortic smooth muscle cells. FGF-13 induced cell growth of lung fibroblasts and aortic smooth muscle cells but had no effect on dermal vascular endothelial cells. FGF-2 induced cell growth in all the three cell types. FGF-13 and FGF-2 had little effect on IL-6 production by lung fibroblasts and aortic smooth muscle cells and substantially enhanced that induced by IL-1alpha. In contrast, FGF-13 and FGF-2 had little effect on IL-6 production by dermal vascular endothelial cells, either alone or in synergy with IL-1alpha.     

Neonatal estrogen stimulates proliferation of periductal fibroblasts and alters the extracellular matrix composition in the rat prostate

The purpose of this study was to examine whether changes in extracellular matrix (ECM) molecules are associated with the growth inhibition and differentiation defects of the prostate gland following neonatal exposure to estradiol. Using immunocytochemistry (ICC), laminin and collagen IV were localized to the basement membrane (BM) as well to the basal lamina of the periductal smooth muscle of the control developing prostates. In contrast, fibronectin and collagen III were localized throughout the stromal ECM. Exposure to neonatal estrogen altered the staining profile for specific ECM molecules. In the estrogenized rats, a thick layer of cells negative for laminin and collagen IV was observed adjacent to the BM. Electron microscopy and ICC for alpha-actin, fibronectin, and vimentin identified this multicellular layer of periductal cells as differentiated fibroblasts. Peripheral to these fibroblasts, actin-positive smooth muscle formed a second layer of periductal stromal cells. PCNA labeling showed that estrogen exposure increased the fibroblast proliferation. Because many periductal fibroblasts were positive for estrogen receptor alpha (ER alpha) in estrogenized rats, a direct effect of estradiol on their proliferation is suggested. Gelatinolytic gels revealed that estrogen exposure did not alter the activity of matrix metalloproteinases associated with tissue remodeling during prostate morphogenesis. However, the periductal fibroblast layer in estrogenized prostates was devoid of urokinase- and tissue-plasminogen activator, which may potentially alter the localized proteolysis involved in matrix remodeling. It is proposed that proliferation of a multicellular layer of periductal fibroblasts in estrogenized prostates results in a physical barrier that constrains branching morphogenesis and blocks paracrine communications between smooth muscle and epithelial cells which normally regulate differentiation.     

Smooth muscle alternative splicing induced in fibroblasts by heterologous expression of a regulatory gene

Alternative splicing is a common mechanism for regulating gene expression in different cell types. In order to understand this important process, the trans-acting factors that enforce the choice of particular splicing pathways in different environments must be identified. We have used the rat alpha-tropomyosin gene as a model system of tissue-specific alternative splicing. Exon 3 of alpha-tropomyosin is specifically inhibited in smooth muscle cells allowing the alternative inclusion of exon 2. We have used a novel gene transfer and selection strategy to detect a gene whose expression in fibroblasts is sufficient to switch them to smooth muscle-specific splicing of alpha-tropomyosin and also alpha-actinin. Extracts from the regulating fibroblasts contain an apparently novel 55 kDa protein which binds to RNA elements required for regulation of tropomyosin splicing. This protein is not detected in extracts of non-regulating cells and is therefore a strong candidate cell-specific splicing regulator. These experiments advance our understanding of smooth muscle splicing regulation as well as establishing a means for direct cloning of tissue-specific splicing regulators which have so far been refractory to biochemical analysis.