Therapeutic results for 100 patients with cancer of the mobile tongue treated with low dose rate interstitial irradiation.

AIM: To evaluate the conservativeness of low dose rate interstitial irradiation (LII) for cancer of the mobile tongue. PATIENTS AND METHODS: Between 1975 and 2002, 100 consecutive patients (71 men, 29 women) underwent LII as curative treatment. Stages were I/IIIII/IV = 16/63/16/4. Seventy-one cases were treated with LII alone and 29 cases treated combined with external irradiation. Median total dose of LH was 70 Gy/7 days. RESULTS: Overall, 5- and 10-year local control and LII-treated patients' survival rates were 93% and 91%, 64% and 57%, respectively. Delayed neck metastases were observed in 21% of initially N0 cases, 56% of which could be salvaged by operation. Early stage and well-differentiated tumors carried better prognoses. CONCLUSION: LII of cancers of the mobile tongue results in good local control and survival. With careful monitoring of patients to ensure early detection of delayed metastases, LII should allow organ conservation and yield favourable therapeutic results compared with those of surgery.

Myosin-Va regulates exocytosis through the submicromolar Ca2+-dependent binding of syntaxin-1A.

Myosin-Va is an actin-based processive motor that conveys intracellular cargoes. Synaptic vesicles are one of the most important cargoes for myosin-Va, but the role of mammalian myosin-Va in secretion is less clear than for its yeast homologue, Myo2p. In the current studies, we show that myosin-Va on synaptic vesicles interacts with syntaxin-1A, a t-SNARE involved in exocytosis, at or above 0.3 microM Ca2+. Interference with formation of the syntaxin-1A-myosin-Va complex reduces the exocytotic frequency in chromaffin cells. Surprisingly, the syntaxin-1A-binding site was not in the tail of myosin-Va but rather in the neck, a region that contains calmodulin-binding IQ-motifs. Furthermore, we found that syntaxin-1A binding by myosin-Va in the presence of Ca2+ depends on the release of calmodulin from the myosin-Va neck, allowing syntaxin-1A to occupy the vacant IQ-motif. Using an anti-myosin-Va neck antibody, which blocks this binding, we demonstrated that the step most important for the antibody's inhibitory activity is the late sustained phase, which is involved in supplying readily releasable vesicles. Our results demonstrate that the interaction between myosin-Va and syntaxin-1A is involved in exocytosis and suggest that the myosin-Va neck contributes not only to the large step size but also to the regulation of exocytosis by Ca2+.

Cerebellar granule cell precursors can differentiate into astroglial cells.

During CNS development, multipotent neural stem cells give rise first to various kinds of specified precursor cells, which proliferate extensively before terminally differentiating into either neurons or glial cells. It is still not clear, however, whether the specified precursor cells are irreversibly determined to differentiate into their particular cell types. In this study, we show that isolated mouse cerebellar granule cell precursors from the outermost, proliferative zone of the external germinal layer can differentiate into astroglial cells when exposed to sonic hedgehog (Shh) and bone morphogenetic proteins. These induced cells initially expressed both glial fibrillary acidic protein and neuronal markers, but they then lost their neuronal markers and acquired S100-beta, a marker of differentiated astroglial cells. These results indicate that at least some granule cell precursors are not irreversibly committed to neuronal development but can be induced to differentiate into astroglial cells by appropriate extracellular signals.

Morphological and biochemical changes of neurofilaments in aged rat sciatic nerve axons.

We have made a detailed comparison of neurofilaments (NFs) in the axons of the sciatic nerves between young and aged rats. In young rats, NF density was similar between proximal and distal sciatic nerve, but it became higher in the proximal region of sciatic nerve of aged rats. In accordance with this morphological change, NF protein content decreased dramatically in the middle region of the sciatic nerves of aged rats. The ratio of NF-M to NF-H in aged rats was lower than that in young rats at the proximal region of sciatic nerves and further decreased in the distal region of sciatic nerve. We analyzed transcription and axonal transport of NF proteins in motor neurons in spinal cord which are the major constituents of sciatic nerve axons. Of the transcripts of the NF subunits, NF-M mRNA was particularly reduced in aged rats. Examination of slow axonal transport revealed that the transport rate for NF-M was slightly faster than that for NF-H in young rats, but slightly slower in aged rats. A decrease in both the synthesis and transport rate of NF-M with aging may contribute to the relative reduction in NF-M in the aged rat sciatic nerve. Although the relationship between NF packing and reduced NF-M is not clear at present, these changes in NFs may be associated with age-dependent axonal degeneration diseases.

Minimal residues in linker domain of syntaxin 1A required for binding affinity to Ca2+/calmodulin-dependent protein kinase II.

The linker domain is important for the conformational change syntaxin 1A, which enables it to act as a SNARE for exocytosis. We found that when applied exogenously, the linker domain is a potent inhibitor of exocytosis through inhibiting interaction between autophosphorylated CaMKII and endogenous syntaxin 1A (Ohyama et al. [2002] J. Neurosci. 22:3342-3351). To identify the simplest and the most potent inhibitor for exocytosis, we further characterized the linker domain and determined the minimal number of residues required for CaMKII binding. The minimal length of the CaMKII-binding site was 145-172 residues and a loss of G172 considerably weakened affinity for CaMKII. The basic amino acid clusters, R151 and K146, were indispensable for binding, whereas R148 was not. A comparison of the CaMKII-binding in several syntaxin isoforms revealed that the substitution of S162 attenuated CaMKII-binding activity. These results suggest that S162 is an important residue as well as the basic amino acid cluster within region 145-172 of the linker domain.

The origin of extensive colour polymorphism in Plateumaris sericea (Chrysomelidae, Coleoptera).

Evidence is presented to demonstrate that colour polymorphism in a beetle arises from structural colours produced by a five-layered reflector in the elytron. The colour of leaf beetles, Plateumaris sericea, ranges across the visible spectrum from blackish-blue to red. The elytra have two distinct layers: epicuticle and exocuticle. Morphological observations reveal that the multilayer structure within the exocuticle differs little among the different colour morphs but the layers within the epicuticle have characteristic thicknesses corresponding to the observed colour. The reflectors, consisting of five layers within the epicuticle, are responsible for all the different colours observed in P. sericea, as shown by theoretical analyses for a multilayer stack, and by showing that removal of the elytral surface, including epicuticle, results in the disappearance of the iridescent colour.

Regulation of exocytosis through Ca2+/ATP-dependent binding of autophosphorylated Ca2+/calmodulin-activated protein kinase II to syntaxin 1A.

Syntaxin 1A/HPC-1 is a key component of the exocytotic molecular machinery, namely, the soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor mechanism. Although >10 syntaxin-binding proteins have been identified, they cannot completely explain the regulation of exocytosis. Thus, novel proteins may interact with syntaxin. Because exocytosis requires both Ca2+ and ATP, we searched for Ca2+/ATP-dependent syntaxin-binding proteins from the rat brain and discovered Ca2+/calmodulin-activated protein kinase II (CaMKII)-alpha. At Ca2+ concentrations of >10(-6) m, only autophosphorylated CaMKII bound to syntaxin. Bound CaMKII was released from syntaxin by EGTA or by phosphatase, indicating that the binding is reversible. CaMKII bound to the linker domain of syntaxin, unlike any other known syntaxin-binding proteins. CaMKII-syntaxin complexes were also detected in synaptosomes by immunoprecipitation, and when reconstituted in vitro, they recruited larger amounts of synaptotagmin and SNAP-25 than syntaxin alone. The microinjected CaMKII-binding domain of syntaxin specifically affected exocytosis in chromaffin cells and in neurons. These results indicate that the Ca2+/ATP-dependent binding of CaMKII to syntaxin is an important process in the regulation of exocytosis.