[Surgical treatment of thymic carcinomas]

Five cases of surgically treated thymic carcinoma are reported. The patients (4 men and a woman) ranged in age from 46 to 76 years old with a mean of 64.6. Four patients were asymptomatic and an abnormal shadow on X-ray films was noted. One remaining patient suffered from hoarseness. One patient had stage II disease and the others had stage III. Surgical tumor resection was performed in all cases. Only 1 patient among the 5 underwent a successful complete resection. Histological examinations of the resected specimens revealed squamous cell carcinoma of thymus. Four specimens were poorly differentiated and 1 is moderately differentiated carcinoma. All patients received radiation therapy post operatively. Three patients are alive without any recurrence 6, 8 and 109 months after the surgery. Thymic carcinomas are frequently invasive or metastatic at the time of diagnosis. But poorly differentiated group, in squamous cell carcinoma, mucoepidermoid carcinoma and besaloid carcinoma, are characterized by a low incidence of local recurrence and distant metastasis. They also have a good sensitivity for the radiation. Therefore complete surgical resection combined with postoperative radiation therapy should be a choice in treating thymic carcinomas. We considered that complete resection and postoperative radiation therapy is a curative therapy for thymic carcinomas.

The mechanism of epidermal hyperpigmentation in dermatofibroma is associated with stem cell factor and hepatocyte growth factor expression

Dermatofibromas have an increased brownish color due to hyperpigmentation of the overlying skin. To determine paracrine factors involved in the epidermal hyperpigmentation, we have studied the expression of cytokines in lesional and nonlesional dermatofibroma skin at the transcriptional and protein levels using reverse transcription polymerase chain reaction and immunohistochemistry, respectively. The number of tyrosinase immuno-positive melanocytes in the pigmented dermatofibroma epidermis is significantly increased (2-fold) compared with nonlesional normal epidermis. Reverse transcription polymerase chain reaction analysis of mRNAs encoding stem cell factor and hepatocyte growth factor demonstrated that there is an accentuated expression of stem cell factor and hepatocyte growth factor transcripts in the lesional dermatofibroma dermis compared with the nonlesional dermis, although there is no difference in their expression between the lesional and nonlesional epidermis. In contrast, mRNA transcripts encoding endothelin-1, growth-related oncogene alpha, and basic fibroblast growth factor are not increased in lesional epidermis or in dermis relative to nonlesional skin. In parallel, immunohistochemical analysis using antibodies to stem cell factor and hepatocyte growth factor reveal a marked immunostaining in growing fibroblastic tumor cells in the dermatofibroma lesions with no detectable staining in the nonlesional dermis, but there is no difference in their immunostaining between the lesional and nonlesional epidermis. Interestingly, and consistent with the increased expression of stem cell factor in lesional dermatofibroma dermis, toluidine blue staining in the dermis revealed a 5-fold increase in the number of mast cells, an indication of their longevity or accumulation induced by stem cell factor. These findings suggest an important role of fibroblastic tumor cell-derived stem cell factor in the mechanism involved in the hyperpigmentation of the dermatofibroma epidermis.

Functional dissection of drosophila capricious: its novel roles in neuronal pathfinding and selective synapse formation

Drosophila Capricious (CAPS) is a transmembrane protein with leucine-rich repeat (LRR) motifs, expressed on small subsets of neurons and muscles, including muscle 12 and the motoneurons that innervate it (muscle 12 MNs). Panmuscle ectopic expression of CAPS alters the target specificity of muscle 12 MNs, indicating that CAPS can function in muscles as a target recognition molecule. In this study, we first examined the effect of ectopic panneural expression of CAPS on the motoneuronal circuit. We found that panneural expression of CAPS alters the pathfinding of muscle 12 MNs. The defect appeared to be caused by changes in the steering behavior of muscle 12 MNs at a specific choice point along their pathway to the target muscle. These results revealed a novel function of CAPS in axon pathfinding. We then performed deletion analyses of CAPS. We expressed CAPS lacking the intracellular domain in all neurons or in all muscles, and studied their ability to induce the pathfinding and targeting phenotypes. We found that the function of muscularly expressed CAPS in target recognition is intracellular domain dependent, whereas the function of neurally expressed CAPS in pathfinding is not, suggesting that CAPS may function in neurons and muscles in a different manner. The requirement of the intracellular domain for the function of muscularly expressed CAPS suggests the presence of a signaling event within muscle cells that is essential for selective synapse formation.

Drosophila synapse formation: regulation by transmembrane protein with Leu-rich repeats, CAPRICIOUS

Upon reaching the target region, neuronal growth cones transiently search through potential targets and form synaptic connections with only a subset of these. The capricious (caps) gene may regulate these processes in Drosophila. caps encodes a transmembrane protein with leucine-rich repeats (LRRs). During the formation of neuromuscular synapses, caps is expressed in a small number of synaptic partners, including muscle 12 and the motorneurons that innervate it. Loss-of-function and ectopic expression of caps alter the target specificity of muscle 12 motorneurons, indicating a role for caps in selective synapse formation.

Requirements of DFR1/Heartless, a mesoderm-specific Drosophila FGF-receptor, for the formation of heart, visceral and somatic muscles, and ensheathing of longitudinal axon tracts in CNS

DFR1 encodes a mesoderm-specific fibroblast growth factor receptor in Drosophila. Here, we identified and characterized a protein-null mutant of DFR1 and examined DFR1 expression in embryos using anti-DFR1 antibody. Mutant phenotypes were completely rescued by a genomic fragment from the DFR1 locus. After invagination, mesodermal cells expressing DFR1 undergo proliferation and spread out dorsally to form a monolayer beneath the ectoderm. In mutant embryos, however, the mesoderm is not capable of extending to the normal dorsal limit and consequently mesodermal cells fail to receive ectodermal signals and thus rendered incapable of differentiating into primordia for the heart, visceral and somatic muscles. DFR1 is also required for normal development of the central nervous system. The absence of DFR1 resulted in the failure of longitudinal glia to enwrap longitudinal axon tracts. DFR1 mutant phenotypes were partially mimicked by the targeted expression of activated Yan, thus demonstrating the MAP kinase pathway to be involved in differentiation of mesoderm.

eagle, a member of the steroid receptor gene superfamily, is expressed in a subset of neuroblasts and regulates the fate of their putative progeny in the Drosophila CNS

We isolated and characterized the eagle gene, encoding a member of the steroid receptor superfamily in Drosophila. In the central nervous system eagle RNA was expressed in a limited number of cells. During stages 10 and 11, eagle RNA expression was observed in four neuroblasts, NB2-4, NB3-3, NB6-4 and NB7-3. Except for NB6-4, eagle RNA expression reached a maximum at the very beginning of expression or in the period of neuroblast delamination. Weak eagle RNA expression was also observed in a few putative progeny of NB7-3 during stages, late 11 and 12. All eagle RNA in abdominal segments disappeared at stage 13. Using an eagle-kinesin-lacZ fusion gene as a reporter, the division, migration, and axonogenesis in eagle-positive cells and their derivatives were examined. At stage 14, several types of neural or glial cells were detected which include EG and EW interneurons joining to the anterior and posterior commissures, respectively. Lack of eagle expression caused altered axonogenesis in an appreciable fraction of eagle-Kinesin-LacZ-positive neurons. Some EG cells failed to acquire the neural fate or underwent an extremely delayed differentiation, while EW neurons produced neurites in abnormal directions, suggesting that eagle may play a critical role in development of the progeny of eagle-positive neuroblasts.

Drosophila phospholipase C-gamma expressed predominantly in blastoderm cells at cellularization and in endodermal cells during later embryonic stages

A Drosophila gene encoding a gamma-type isozyme of phosphoinositide-specific phospholipase C (PLC) was isolated and characterized. The gene, termed plc-gamma d, was mapped at position 14B-C of the X chromosome. The encoded protein, termed PLC-gamma D, contains X and Y regions, common to all known PLC isozymes. The two regions are split by a Z region that comprises two src homology 2 and one src homology 3 domains and is characteristic of gamma-type mammalian PLC (PLC-gamma 1 and -gamma 2). The deduced amino acid sequence of PLC-gamma D shows overall similarity to mammalian PLC-gamma s; no large deletion was observed except the short C-terminal extended region. In particular, the two split catalytic domains (X and Y regions) and the regulatory Z region including the src homology 2 and src homology 3 domains are well conserved. The mRNA is expressed throughout development, but expression is relatively higher during the embryonic stage, suggesting fundamental and important roles in both cell proliferation and differentiation. Distribution of the mRNA during embryogenesis, as analyzed by whole amount in situ hybridization, revealed that the mRNA emerges and reaches maximum levels at the cellular blastoderm stage and then decreases rapidly to a lower level. In later embryonic stages, invaginated anterior and posterior midgut primordia show high levels of mRNA expression, and fused midgut also maintains a high level of expression. In other tissues and cells, the mRNA was detected at lower levels. These results indicate that Drosophila PLC-gamma may be involved in universal cellular processes mediated possibly by receptor tyrosine kinases during embryogenesis and may also play specific roles during cellularization and midgut differentiation.

Two FGF-receptor homologues of Drosophila: one is expressed in mesodermal primordium in early embryos

The fibroblast growth factor (FGF)/receptor system is thought to mediate various developmental events in vertebrates. We examined molecular structures and expression of DFR1 and DFR2, two Drosophila genes closely related to vertebrate FGF-receptor genes. DFR1 and DFR2 proteins contain two and five immunoglobulin-like domains, respectively, in the extracellular region, and a split tyrosine kinase domain in the intracellular region. In early embryos, DFR1 RNA expression, requiring both twist and snail proteins, is specific to mesodermal primordium and invaginated mesodermal cells. At later stages, putative muscle precursor cells and cells in the central nervous system (CNS) express DFR1. DFR2 expression occurs in endodermal precursor cells, CNS midline cells and certain ectodermal cells such as those of trachea and salivary duct. FGF-receptor homologues in Drosophila would thus appear essential for generation of mesodermal and endodermal layers, invaginations of various types of cells, and CNS formation.

Identification of seven novel protein-tyrosine kinase genes of Drosophila by the polymerase chain reaction

We used the polymerase chain reaction to identify 7 novel tyrosine-kinase genes (dtk1 to -7) in Drosophila melanogaster, dtk4 coded for a part of the kinase catalytic domain nearly identical in sequence to that of the human receptor for insulin-like growth factor 1, whereas sequences encoded by dtk1 and dtk2 were highly homologous to that of the chicken fibroblast growth factor receptor.