Local motion of crosslinks for poly (methyl methacrylate) gels by the fluorescence depolarization method

Poly(methyl methacrylate) (PMMA) gels labeled at crosslinks with anthracene were prepared. Anthracene fluorescence depolarization was monitored to probe the local motion of crosslinks for PMMA gels at different equilibrium swelling states. The relaxation times and the activation energies of local motion were measured for PMMA gels at the swollen states in various solvents through fluorescence anisotropy decays. The local motion of PMMA gel at crosslinks became faster with the increase of swelling ratio. When the swelling ratios were almost the same, the mobility of crosslinks was the same irrespective of the molecular weights between crosslinks. These results indicate that the local motion of crosslinks for PMMA gel is mainly governed by the segment density of network chains in the vicinity of crosslinks. Received: 31 March 1997/Revised: 11 April 1997/Accepted: 21 April 1997     

Pulse width tunable subpicosecond pulse generation from an activelymodelocked monolithic MQW laser/MQW electroabsorption modulator

Actively modelocked pulses are generated from a 1.59 μm MQW laser integrated with an MQW electroabsorption modulator driven at the monolithic cavity frequency. The pulse width is controlled from 39 ps to 0.55 ps by changing the inverse bias voltage applied to the electroabsorption modulator and by linear pulse compression using a fibre     

1H-NMR study of inter-segmental hydrogen bonds in sperm whale and horse apomyoglobins

NMR signals for HisB5 N(delta)H and HisEF5 N(epsilon)H protons of sperm whale and horse apomyoglobins were assigned and compared with the corresponding signals of the holoproteins in terms of pH and temperature dependence behaviors of their shifts and line widths in order to gain insight into structural difference between the apoproteins and the holoproteins. Since these protons are involved in internal hydrogen bonds at the interfaces between the B helix and the GH corner and between the EF corner and the H helix, local structures of the interfaces in these proteins have been inferred from the analyses of these signals. A large difference in the line width of HisEF5 N(epsilon)H proton signal between the apoproteins and the holoproteins strongly suggested that a sizable structural alteration is induced in the EF-H interface by the removal of heme. However, the results for HisB5 N(delta)H proton resonance indicated the absence of a significant structural alteration in the B-GH interface by heme extraction. These results are consistent with the data obtained from mutation [Hughson, F. M. & Baldwin, R. L. (1989) Biochemistry 28, 4415-4422] and amide-proton-exchange kinetic [Hughson, F. M., Wright, P. E. & Baldwin, R. L. (1990) Science 249, 1544-1548] studies, which indicated that the A, B, G and H helices in apomyoglobin maintain the same packing as they do in holoprotein.     

Clustered localization of oligomeric Nef protein of human immunodeficiency virus type 1 on the cell surface

We studied human immunodeficiency virus type 1 (HIV-1) Nef protein biochemically and histologically. HIV-1 Nef, derived from baculosystem and from cells infected with HIV-1, formed homomeric monomers, dimers, trimers, and further polymers. These oligomers were non-covalently associated. In cells infected with HIV-1, Nef molecules were clustered at the cell surface as well as cytoplasm. Our previous results have indicated that the Nef on the surface of cells infected with HIV-1 is cytotoxic against uninfected CD4+ T cells. Thus, it is very likely that the HIV-1-mediated cytotoxic reaction is due, at least in part, to the clustered localization of oligomeric Nef on the cell surface.     

First sea trial of FSK heterodyne optical transmission system usingpolarisation diversity

Operations of an FSK heterodyne optical transmission system on the cable ship during the cable-laying, holding, and recovering process in a 6000 m-deep sea trial is demonstrated. It is shown that polarisation diversity is a powerful technique for application to optical fibre coherent systems in submarine cable systems     

Microstrip-fed crossed-slot array antenna

A microstrip-fed crossed-slot array antenna having a circular polarisation is developed. First, a single crossed-slot antenna, that can radiate a circularly polarised wave in the broadside direction, is designed and its coupling level to the microstrip line is analysed. Based on this result, an eight-element crossed-slot array is designed and its characteristics are experimentally investigated at 12 GHz band. The return loss of -17 dB is obtained at the design frequency of 11.85 GHz, and the axial ratio of less than 3 dB is achieved over the fractional bandwidth of 5%.     

Simple technique for pancreatogastrostomy and the histological findings of pancreatogastric anastomosis

The leakage of pancreatic juice is the most serious complication after pancreatoduodenectomy. In an attempt to lessen the incidence of this complication, we have developed a simple technique for the anastomosis of pancreatogastrostomy. Since March 14, 1995, we have already performed surgical procedures on 8 cases of pancreatogastrostomy using this technique and as yet have never experienced fatal complications. We report the autopsy findings of pancreatogastric anastomosis histologically. The specimen taken from the anastomosis reveals good mucosal continuity. This result suggests the importance of reliable sutures between the pancreatic parenchyma and the full thickness of the gastric wall for the anastomosis of pancreatogastrostomy.     

Tissue fibronectin is an endogenous ligand for galectin-1

A 14K beta-galactoside-binding lectin (galectin-1) is present in many animal tissues. In a search for endogenous ligands, we surveyed galectin-1-binding proteins in human placenta. Extract of human placenta with 2 M urea was applied to a Sepharose 4B column conjugated with galectin-1 purified from frog (Rana catesbeiana) eggs. Two major proteins eluted with 100 mM lactose from the column-bound fraction showed apparent molecular masses of 220 and 180 kDa on SDS-PAGE under reducing conditions. Western blotting analysis using monoclonal antibodies indicated that these proteins were fibronectin and laminin, respectively. Most placental and amniotic fibronectins bound strongly to the column, whereas almost all plasma fibronectin passed through the column. The galectin-1, fibronectin and laminin were immunohistochemically shown to be co-localized in the extracellular matrix of placental tissue. In a cell attachment assay, rhabdosarcoma cells adhered to a plate coated with placental fibronectin, even in the presence of GRGDS peptide, if galectin-1 were also present. This adhesive effect of galectin-1 was inhibited by lactose. These results indicate that tissue fibronectin, as well as laminin, serve as endogenous ligands for galectin-1, suggesting that galectin-1 may play a role in assembly of the extracellular matrix, or in the control of cell adhesion based on lectin-extracellular matrix interaction.