Calcium-Dependent Persistent Facilitation of Spike Backpropagation in the CA1 Pyramidal Neurons

Sodium-dependent action potentials initiated near the soma are known to backpropagate over the dendrites of CA1 pyramidal neurons in an activity-dependent manner. Consequently, later spikes in a train have smaller amplitude when recorded in the apical dendrites. We found that depolarization and resultant Ca²⁺ influx into dendrites caused a persistent facilitation of spike backpropagation. Dendritic patch recordings were made from CA1 pyramidal neurons in mouse hippocampal slices under blockade of fast excitatory and inhibitory synaptic inputs. Trains of 10 backpropagating action potentials induced by antidromic stimulation showed a clear decrement in the amplitude of later spikes when recorded in the middle apical dendrites. After several depolarizing current pulses, the amplitude of later spikes increased persistently, and all spikes in a train became almost equal in size. BAPTA (10 mM) contained in the pipette or low-Ca^(2+) perfusing solution abolished this depolarization-induced facilitation, indicating that Ca²⁺ influx is required. This facilitation was present in Gα_q knock-out mice that lack the previously reported muscarinic receptor-mediated enhancement of spike backpropagation. Therefore, these two forms of facilitation are clearly distinct in their intracellular mechanisms. Intracellular injection of either calmodulin binding domain (100 μM) or Ca²⁺/calmodulin-kinase II (CaMKII) inhibitor 281–301 (10 μM) blocked the depolarization-induced facilitation. Bath application of a membrane-permeable CaMKII inhibitor KN-93 (10 μM) also blocked the facilitation, but KN-92 (10 μM), an inactive isomer of KN-93, had no effect. These results suggest that increases in [Ca²⁺)]_i cause persistent facilitation of spike backpropagation in the apical dendrite of CA1 pyramidal neuron by CaMKII-dependent mechanisms

フィブリノゲン／トロンビンコーティングコラーゲンによる肺瘻の修復過程

広島大学(Hiroshima University)博士(医学)Doctor of Philosophy in Medical Sciencedoctora

A Novel Grafting of Polymers onto the Surface of Graphene Oxide

A simple grafting of polymers onto graphene oxide (GO) was achieved by polymer radical trapping, ligand-exchange reaction, and surface initiated cationic and anionic graft polymerization. Grafting of poly(ethylene glycol) (PEG) onto GO was successfully achieved by trapping of PEG radicals formed by thermal decomposition of PEG macroazo initiator to give PEG-grafted GO. The grafting of copolymers containing vinyl ferrocene moieties onto GO surfaces was also successfully achieved by the ligand-exchange reaction between ferrocene moieties of these copolymers and GO. Carboxyl groups on GO have an ability to initiate the cationic polymerizations of vinyl monomers, such as N-vinylcarbazole and isobutyl vinyl ether. The corresponding vinyl polymers were grafted onto GO, during the cationic polymerization, based on the termination of growing polymer cation by counter anion (carboxylate) groups on GO. It was found that the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides was successfully initiated by potassium carboxylate groups on GO, introduced by neutralization of carboxyl groups with KOH, to give the corresponding polyester-grafted GO. The dispersibility of GO in organic solvents was remarkably improved by the grafting of the above polymers onto GO. In addition, easy preparation of reduced GO-based conducting polyaniline composite organogel will be discussed

Dual-modality imaging with 99mTc and fluorescent indocyanine green using surface-modified silica nanoparticles for biopsy of the sentinel lymph node: an animal study

BACKGROUND: We propose a new approach to facilitate sentinel node biopsy examination by multimodality imaging in which radioactive and near-infrared (NIR) fluorescent nanoparticles depict deeply situated sentinel nodes and fluorescent nodes with anatomical resolution in the surgical field. For this purpose, we developed polyamidoamine (PAMAM)-coated silica nanoparticles loaded with technetium-99m ((99m)Tc) and indocyanine green (ICG). METHODS: We conducted animal studies to test the feasibility and utility of this dual-modality imaging probe. The mean diameter of the PAMAM-coated silica nanoparticles was 30 to 50 nm, as evaluated from the images of transmission electron microscopy and scanning electron microscopy. The combined labeling with (99m)Tc and ICG was verified by thin-layer chromatography before each experiment. A volume of 0.1 ml of the nanoparticle solution (7.4 MBq, except for one rat that was injected with 3.7 MBq, and 1 μg of an ICG derivative [ICG-sulfo-OSu]) was injected submucosally into the tongue of six male Wistar rats. RESULTS: Scintigraphic images showed increased accumulation of (99m)Tc in the neck of four of the six rats. Nineteen lymph nodes were identified in the dissected neck of the six rats, and a contact radiographic study showed three nodes with a marked increase in uptake and three nodes with a weak uptake. NIR fluorescence imaging provided real-time clear fluorescent images of the lymph nodes in the neck with anatomical resolution. Six lymph nodes showed weak (+) to strong (+++) fluorescence, whereas other lymph nodes showed no fluorescence. Nodes showing increased radioactivity coincided with the fluorescent nodes. The radioactivity of 15 excised lymph nodes from the four rats was assayed using a gamma well counter. Comparisons of the levels of radioactivity revealed a large difference between the high-fluorescence-intensity group (four lymph nodes; mean, 0.109% ± 0.067%) and the low- or no-fluorescence-intensity group (11 lymph nodes; mean, 0.001% ± 0.000%, p < 0.05). Transmission electron microscopy revealed that small black granules were localized to and dispersed within the cytoplasm of macrophages in the lymph nodes. CONCLUSION: Although further studies are needed to determine the appropriate dose of the dual-imaging nanoparticle probe for effective sensitivity and safety, the results of this animal study revealed a novel method for improved node detection by a dual-modality approach for sentinel lymph node biopsy

A Study on the Stress Distribution Around Filler of Polymer Composite Materials

In this paper, process of bonding and bonding rupture of matrix and spheroid oxidizing iron grains contained in polyethylene film are photographically observed by means of optical microscope, stress distribution around filler is sought for by finite element method, and the process of rupture of bonding by stress concentration is studied

A Study on the Characteristics at Low Temperature of Welded Polycarbonate

In this study we investigated the tensile characteristics of welded polycarbonate at low temperature. This study intends to clarify the low temperature characteristics of welded part comparing with those of base material. The results of some measurements on the tensile properties from 20°C down to -70℃ are reported and the changes in tensile properties under low temperature atmosphere are discussed. Furthermore, notch and load velocity effects on the brittle fracture tendency are also discussed. Conclusions obtained in this study are summarized as follows; 1) Both welded part and base material of polycarbonate are strengthened at low temperature. 2) Welding joint efficiency of polycarbonate is very good even at low temperature. 3) Notch and load velocity effects are observed both on the base and the welded materials. 4) Correlations are observed between fracture surfaces and mechanical testing results

Amino acid sequence of retinal transducin at the site ADP-ribosylated by cholera toxin

Transducin was [32P]ADP-ribosylated by cholera toxin in bovine retinal rod outer segments and then partially purified on ω-amino octyl agarose to remove other ADP-ribosylated proteins. Trypsin digestion of the ADP-ribosylated transducin and further purification using boronate-polyacrylamide beads and high performance liquid chromatography yielded a single radiolabeled tetrapeptide, Ser-Arg-Val-Lys. The ADP-ribose is linked to the guanidinium group of arginine