Extraocular muscles involved in convergence are innervated by an additional set of palisade endings that may differ in their excitability: A human study

Palisade endings are located at the myotendinous junction of extraocular muscles in most mammals. Irrespective of their unclarified function as motor or sensory nerve endings, a specialized role in convergence is proposed, based on their high number in the medial rectus muscle (MR). Further support comes from a study in monkey demonstrating that only the MR and inferior rectus muscle (IR) contain an additional population of palisade endings that express the calcium-binding protein calretinin (CR) in addition to choline acetyltransferase (ChAT). Here we studied, whether CR-positive palisade endings are present in human as well and confined to extraocular muscles most active during convergence. The systematic analysis of all eye muscles of 17 human specimen revealed that only the MR and IR contain an additional population of CR-positive palisade endings and multiple en-grappe endings, which target non-twitch muscle fibers along their whole length. Approximately 80% of all palisade endings in the MR expressed CR. Furthermore, the intrafusal muscle fibers of some muscle spindles in the MR were innervated by CR-positive annulospiral nerve endings that transmit the signals of muscle length changes to the brain. All extraocular muscles contained few thin CR-positive, but ChAT-negative nerve fibers, possibly representing free sensory or autonomic endings arising from the trigeminal ganglion. As in monkey, in the medial periphery of the human oculomotor nucleus ChAT-positive neurons were found to co-express CR. Therefore these neurons most likely represent the cell bodies of CR-positive palisade endings in the MR. Unlike in monkey, these neurons do not lie within a compact cell group, but are more scattered. In conclusion, the MR and IR in human contain two histochemically different populations of palisade and multiple endings that may contribute to ocular alignment and convergence in a different way.

A role for decorin in the structural organization of periodontal ligament

Decorin is a small leucine-rich proteoglycan that interacts with several matrix molecules, including various types of collagen and growth factors, and suppresses the growth of neoplastic cells by an epidermal growth factor (EGF) receptor-mediated pathway. Decorin is abundantly expressed in the periodontal connective tissues during development and tissue maintenance. In periodontal disease, which is one of the most common diseases in the human kind, the level of decorin is decreased in the periodontal connective tissue. Abnormal expression of decorin may also associate with certain inherited disorders that involve increased susceptibility to severe periodontal disease in the early childhood. Therefore, we investigated the periodontal tissues of mice with targeted disruption of the decorin gene. Gross and microscopic analyses showed that decorin-deficient mice appeared to have normal tooth development and eruption, and there were no signs of periodontal disease. However, electron microscopic analysis revealed abnormal morphology and organization of the collagen fibrils in the periodontal ligament. The number of periodontal ligament fibroblasts in the decorin-deficient mice was also increased about two-fold as compared with the wild-type mice. In cell culture, ectopic overexpression of decorin in NIH 3T3 fibroblasts or decorin added exogenously to periodontal fibroblasts suppressed cell growth. However, blocking the EGF receptor tyrosine kinase activity did not prevent the decorin-elicited growth suppression in periodontal fibroblasts. Additionally, decorin did not induce a marked increase in the relative expression of p21 mRNA in periodontal fibroblasts. Therefore, decorin appeared to regulate growth of normal periodontal fibroblasts by a mechanism distinct from that reported for neoplastic cells. The findings demonstrate that decorin plays a role in the organization of collagen fibrils and regulates cell proliferation in the periodontal ligament.

Multifocal oncocytic adenomatous hyperplasia of the parotid gland. A case report

A case report of a multifocal oncocytic adenomatous hyperplasia occurring in a parotid gland is presented. The differential diagnosis of (multicystic) Warthin's tumor is discussed.

Distribution of laminin and fibronectin isoforms in oral mucosa and oral squamous cell carcinoma

The expression of laminin and fibronectin isoforms varies with cellular maturation and differentiation and these differences may well influence cellular processes such as adhesion and motility. The basement membrane (BM) of fetal oral squamous epithelium contains the laminin chains, alpha2, alpha3, alpha5, beta1, beta2, beta3, gamma1 and gamma2. The BM of adult normal oral squamous epithelium comprises the laminin chains, alpha3, alpha5, beta1, beta3, gamma1 and gamma2. A re-expression of the laminin alpha2 and beta2 chains could be shown in adult hyperproliferative, dysplastic and carcinomatous lesions. In dysplasia and oral squamous cell carcinoma (OSCC), multifocal breaks of the BM are present as indicated by laminin chain antibodies. These breaks correlate to malignancy grade in their extent. Moreover, in the invasion front the alpha3 and gamma2 chain of laminin-5 can immunohistochemically be found outside the BM within the cytoplasm of budding carcinoma cells and in the adjacent stroma. The correlation between the morphological pattern of invasive tumour clusters and a laminin-5 immunostaining in the adjacent stroma may suggest, first, that a laminin-5 deposition outside the BM is an immunohistochemical marker for invasion and second, that OSCC invasion is guided by the laminin-5 matrix. Expression of oncofetal fibronectins (IIICS de novo glycosylated fibronectin and ED-B fibronectin) could be demonstrated throughout the stromal compartment. However, the ED-B fibronectin synthesizing cells (RNA/RNA in situ hybridization) are confined to small stroma areas and to single stroma and inflammatory cells in the invasion front. A correlation of the number of ED-B fibronectin synthesizing cells to malignancy grade could not be seen. ED-B fibronectin mRNA-positive cells seem to be concentrated in areas of fibrous stroma recruitment with a linear alignment of stromal fibro-/myofibroblasts (desmoplasia). Double staining experiments (ED-B fibronectin in situ hybridization and alpha-smooth muscle actin immunohistochemistry) indicated that the stroma myofibroblasts are a preferential source of ED-B fibronectin. In conclusion, in OSCC, a fetal extracellular matrix conversion is demonstrable. Tumour cells (laminin alpha2 and beta2 chain) and recruited stromal myofibroblasts (oncofetal ED-B fibronectin) contribute to the fetal extracellular matrix milieu.

Differential expression of laminin chains in the human major salivary gland

Laminin represents a macromolecule family. The heterotrimeric isoforms of laminin can be determined by immunohistochemical demonstration of the single chains. The laminin chain heterogeneity of the basement membrane in adult human major salivary glands was evaluated in relation to cellular differentiation of the epithelia and the stromal compartment. Monoclonal antibodies to the laminin alpha1, alpha3 (BM165) chains and epiligrin reacted with the basement membranes of serous and mucous acini and of intercalated, striated and excretory ducts. As evidenced by a double-labelling technique, the alpha2 chain showed a spatial association with the myoepithelium of the acini, whereas the ductal basement membranes containing no myoepithelial cells were negative. Almost exclusively, beta1 chain was detected in acinar basement membrane, beta2 chain whereas in ductal basement membrane. Gamma2 chain is a unique chain belonging to the laminin-5 isoform. It was restricted to the ductal basement membrane. Alpha1, alpha2, beta1, beta2 and gamma1 chains were detected in nerves of salivary tissue and alpha1, alpha3, beta1, beta2 and gamma1 chains and epiligrin in blood vessels. Our results indicate that the acinar ductal unit contains basement membranes with different isoforms, which relate to cell differentiation and cell function.

[Basaloid squamous epithelial carcinoma (basaloid-squamous carcinoma) of the mouth floor. Differential diagnosis and response to neoadjuvant chemotherapy]

The basaloid squamous cell carcinoma (BSCC) is a variant of squamous cell carcinoma, having histologically distinctive features and appearing in the oral cavity, upper respiratory tract and esophagus. Histological hallmarks are the presence of a basaloid component in intimate association with squamous cell carcinoma. The basaloid component is characterized by tightly packed nests of cells with scant cytoplasm and hyperchromic nuclei without visible nucleoli and an increased mitosis rate. Basaloid squamous cell carcinoma is said to have a higher malignant potential than common oral squamous cell carcinoma with an increased incidence of regional lymph-node metastases and distant metastases. Our finding of a Ki-67 index of 30% and the immunohistochemical demonstration of p53 protein speaks well for enhanced aggressive biological behavior. The differential diagnosis includes the adenoid cystic, mucoepidermoid, neuroendocrine, adenosquamous and conventional oral squamous cell carcinoma. Because of early dissemination, radical surgical treatment and additional radiation therapy are considered necessary. Our findings indicate that partial clinical and histological tumor regression occurs after systemic neoadjuvant chemotherapy.