A. H. M. Shabana

Infiltrating (intramuscular) benign lipoma of the head and neck

Abstract Lipomas are benign soft-tissue mesenchymal tumors commonly occurring in the region of the neck, and less frequently on the back, arm, shoulder, anterior chest wall, breast, thigh, abdominal wall, leg, forehead, and face, in that order. 1 Several cases of oral lipomas have been reported. They are generally found in the tongue, buccal mucosa, gingiva, and labial and buccal folds. 2,3 Infiltrating lipoma, also referred to as an intramuscular lipoma, is an unusual form of this benign neoplasm, originating between skeletal muscle bundles and infiltrating through the intramuscular septa. 4–7 These lipomas are generally found on the upper or lower limbs, and are exceedingly rare in the oral cavity. Only six cases have been reported. 5,8–11 Because of the rarity of these tumors and their high rate of recurrence without adequate surgery.

A comparative biochemical and immunological analysis of cytokeratin patterns in the oral epithelium of the miniature pig and man

In man, cytokeratin constitutes a family of 19 polypeptides that show different but distinct distribution patterns in the various epithelia. Changes in these patterns may occur during epithelial development and differentiation. The cytokeratin patterns in the oral mucosa of the miniature pig, an animal used in studies of wound healing, were investigated. Surgical biopsies were obtained from the gingiva, hard palate and alveolar mucosa of both man and pig. The cytokeratins were analysed by immunofluorescence, two-dimensional gel electrophoresis and by immunoblotting. Nine monoclonal antibodies were used to identify the different cytokeratin polypeptides in cryostat sections. Two-dimensional gel electrophoresis showed that pig oral mucosa contains at least 10 different polypeptides, five of the acidic type I and five of the basic type II cytokeratins. These were different from the human cytokeratin polypeptides and accordingly were designated P1-P10, according to their molecular weight and isoelectric mobility. Their molecular weight varied between 48 and 69 kdalton and the pHi varied between 5 and 7.3. Immunoblotting showed the monoclonal antibody Ks 13.1 (anticytokeratins Nos 13 and 14) to cross-react with the pig polypeptides P10 and P8. Immunolocalization showed that all the antibodies cross-reacted with the pig tissue except Ks 19.1 (anticytokeratin No. 19). It was possible to differentiate between pig alveolar mucosa, which expressed only P3, P4, P5, P8 and P10, and the gingival and hard palatal mucosae, which expressed all 10 polypeptides except P5. This distinction was made by antibody 6B10 (anticytokeratin No. 4), which reacted only with alveolar mucosa; antibody Ks 13.1, which strongly reacted with uncornified mucosa but weakly with cornified mucosa (gingiva and palate); and any of RKSE60, Kk 8.60 or EE21.6 (anticytokeratin No. 10, anticytokeratins Nos 10 and 11 and anticytokeratins Nos 1, 2, 10 and 11, respectively), which reacted strongly with cornified mucosa but weakly, if at all, with uncornified mucosa. These findings provide a baseline for studies on epithelial differentiation in the miniature pig such as in wound healing.

Involvement of Desmoplakin Phosphorylation in the Regulation of Desmosomes by Protein Kinase C, in HeLa Cells

In the present study, we have examined how modulation of protein kinase C (PKC) activity affected desmosome organization in HeLa cells. Immunofluorescence and electron microscopy showed that PKC activation upon short exposure to 12-O-tetradecanoylphorbol 13-acetate (TPA) resulted in a reduction of intercellular contacts, splitting of desmosomes and dislocation of desmosomal components from the cell periphery towards the cytoplasm. As determined by immunoblot analysis of Triton X-100-soluble and -insoluble pools of proteins, these morphological changes were not correlated with modifications in the extractability of both desmoglein and plakoglobin, but involved almost complete solubilization of the desmosomal plaque protein, desmoplakin. Immunoprecipitation experiments and immunoblotting with anti-phosphoserine, antiphosphothreonine and anti-phosphotyrosine antibodies revealed that desmoplakin was mainly phosphorylated on serine and tyrosine residues in both treated and untreated cells. While phosphotyrosine content was not affected by PKC activation, phosphorylation on serine residues was increased by about two-fold. This enhanced serine phosphorylation coincided with the increase in the protein solubility, suggesting that phosphorylation of desmoplakin may be a mechanism by which PKC mediates desmosome disassembly. Consistent with the loss of PKC activity, we also showed that down-modulation of the kinase (in response to prolonged TPA treatment) or its specific inhibition (by GF 109203X) had opposite effects and increased desmosome formation. Taken together, these results clearly demonstrate an important role for PKC in the regulation ofdesmosomal junctions in HeLa cells, and identify serine phosphorylation of desmoplakin as a crucial event in this pathway.

Desmosomes are Regulated by Protein Kinase C in Primary Rat Epithelial Cells

In the present study, we addressed the possible relevance of protein kinase C (PKC) in the regulation of intracytoplasmic desmosome assembly. Treatment of cultured rat lingual and epidermal keratinocytes with a potent and highly selective PKC inhibitor (GF109203X) induced an increase in granular labelling for major desmosomal proteins, desmoplakins, desmoglein and plakoglobin, both intracellularly and at the cell surface. This was associated with the formation of ultrastructurally recognizable desmosomes deep in the cytoplasm and increase in intercellular desmosome number. In contrast, PKC activation upon short exposure to 12-O-tetradecanoylphorbol 13-acetate (TPA) resulted in altered cell morphology, loss of intercellular contact and accumulation of desmosomal proteins in the juxtanuclear zone. On the other hand, PKC depletion by long term TPA treatment re-established cell-cell contact, where desmosomal markers were exclusively redistributed. Taken together, these results suggest that inhibition of PKC is required for intracytoplasmic as well as intercellular desmosome assembly, whereas its activation may regulate disassembly process.

Histological evaluation of natural coral skeleton as a grafting material in miniature swine mandible

Natural coral skeleton (NCS) has recently been proposed as a bone graft substitute that enhances bone formation. The present paper describes the effects of implanting NCS in bone cavities prepared in the mandibles of miniature pig, and compares these with the effects of two alloplastic materials; a tricalcium phosphate (TCP) and a porous hydroxyapatite (PHA). On 11 pigs, 5 × 5 mm windows were created through alveolar bone of the four mandibular incisors. Three cavities were filled with the various materials and the fourth was left unfilled. The animals were slaughtered at 0, 1, 2, 4, 12, 26 and 52 weeks post-operatively and the tissues were examined histologically. Healing completed at 26 weeks for NCS and TCP, and at 52 weeks for PHA. NCS granules provided surface for cell attachment and deposition of a distinguishable organic matrix two weeks post-operatively. This matrix developed to bone after four weeks. The granules gradually resorbed and were replaced by bone at 52 weeks. The excellent properties of NCS, biocompatibility, porosity and osteogenic effect make us suggest that it might be a suitable replacement for bone grafting.

H-7 stimulates desmosome formation and inhibits growth in KB oral carcinoma cells

Protein kinase inhibitor H‐7 was reported to stimulate desmosome formation in normal keratinocytes and to inhibit proliferation of neural cell lines. In the present study, the effects of this inhibitor on adhesion and growth of KB human oral carcinoma cells were investigated. H‐7 was found to enhance desmosome assembly, as evidenced by an increased punctate labeling for the major desmosomal markers. Immunogold labeling confirmed the formation of desmosomes both at the cell surface and in the cytoplasm. In order to assess cell proliferation and possible correlation with adhesion, confluent cultures were treated and both adherent and detached cell fractions were counted. Under serum‐free conditions, H‐7 significantly reduced cell detachment. In contrast, EGF stimulated cell detachment, and this effect was abolished when cells were simultaneously treated with both EGF and H‐7. Total cell counts were also significantly reduced by H‐7, both in the presence and absence of EGF. Using the TUNEL technique, labeled cells were increased after H‐7 treatment, thus implicating protein kinase inhibition in cell death. These results indicate that H‐7 inhibits growth and stimulates adhesion of KB carcinoma cells. Microsc. Res. Tech. 43:233–241, 1998.

Ultrastructural study of the effects of coral skeleton on cultured human gingival fibroblasts in three-dimensional collagen lattices

Natural coral skeleton has recently been introduced as a bone graft substitute which enhances bone formation in man and animals. The effects of NCS on cultured human cells has not previously been investigated. In the present study we report these effects as studied by light microscopy, transmission and scanning electron microscopy in three-dimensional culture. The results showed that natural coral skeleton does not inhibit the normal function of fibroblasts in contracting collagen lattices. After 8 weeks, the cells maintained a healthy ultrastructural morphology. At the collagen/coral interface, the cells were well-spread and attached to the surface by numerous adhesion plaques. Evidence for biosynthetic activity was also observed; the cells showed numerous ribosomes, mitochondria and prominent rough endoplasmic reticulum. Extracellularly, a perigranular dense matrix, appearing as nodules in the SEM, was deposited on the coral surface. This matrix was made of highly organized fibrils lacking periodicity, and a ground substance. The present study shows that coral was well-tolerated by human gingival fibroblasts, and that it provided a surface for cell spreading, attachment and deposition of the special extracellular matrix.