Conventional stimuli-responsive hydrogels provide one unique action, either swelling or deswelling in response to external stimuli such as a change in solvent composition, 1,2 pH, 1-3 temperature, 4-6 etc. Here we report a novel polymeric gel which autonomously swells and deswells periodically in a closed homogeneous solution without any external stimuli, similar to autonomic phenomena in life such as heartbeat. The mechanical oscillation is achieved by inducing the Belousov-Zhabotinsky (BZ) reaction 7 within the gel. We prepare a copolymer gel of N-isopropylacrylamide (IPAAm) in which ruthenium(II) tris-(2,2′-bipyridine) (Ru(bpy) 3 2+ ), a catalyst for the BZ reaction, is covalently bonded to the polymer chain. The poly(IPAAmco-Ru(bpy) 3 ) gel swells and deswells at the oxidized and reduced states of Ru(bpy) 3 , respectively. The BZ reaction in the gel generates periodic redox changes of Ru(bpy) 3 , and the chemical oscillation induces mechanical oscillation of the polymer network.Many polymeric gels undergo abrupt volume change in response to external stimuli, and they have been utilized to design intelligent materials which imitate stimuli-responding functions in living systems, such as actuators 8,9 and pulsatile drug release devices, 10-12 etc. In contrast to the unique gel action of either swelling or deswelling toward a stable equilibrium state, many physiological systems maintain rhythmical oscillations in a nonequilibrium state, as represented by the autonomic heartbeat, brain waves, periodic hormone secretion, etc. If such self-oscillation without any external stimuli is achieved for gels, a new concept will be created for functional materials that work under dynamic oscillating states similar to life systems, such as self-walking actuators, new pacemakers and timers, drug delivery systems synchronized with human circadian rhythms, etc. For example, a strategy for an oscillatory drug release system utilizing a gel membrane coupled with an enzyme reaction is studied numerically by Siegel et al. 13 In a previous report, 14 we achieved periodic swelling-deswelling changes of gels soaked in an autonomous pH-oscillating solution in a continuously-stirred tank reactor. However, gels that provide volume oscillation without external control in a closed solution have not been developed yet. In gel systems, the only oscillatory phenomenon known both theoretically and experimentally is sol/gel transition.  The BZ reaction is well-known for exhibiting temporal and spatial oscillating phenomena with periodic redox changes of the catalysts in a closed solution, and its significance has been recognized in understanding some aspects of life phenomena in transmission of information, pattern recognition and selforganization, etc. 18-21 We attempt to convert the chemical oscillation of the BZ reaction to the mechanical changes of gels and generate an autonomic swelling-deswelling oscillation under nonoscillatory outer conditions. Whereas hydrogels have been used as the BZ reaction medium in order to suppress ...
Fas is a type I membrane protein which mediates apoptosis. Fas ligand (FasL) is a 40 kDa type II membrane protein expressed in cytotoxic T cells upon activation that belongs to the tumor necrosis factor (TNF) family. Here, we found abundant cytotoxic activity against Fas‐expressing cells in the supernatant of COS cells transfected with human FasL cDNA but not with murine FasL cDNA. Using a specific polyclonal antibody against a peptide in the extracellular region of human FasL, a protein of 26 kDa was detected in the supernatant of the COS cells. The signal sequence of granulocyte colony‐stimulating factor was attached to the extracellular region of human FasL. COS cells transfected with the cDNA coding for the chimeric protein efficiently secreted the active soluble form of human FasL (sFasL). Chemical crosslinking and gel filtration analysis suggested that human sFasL exists as a trimer. Human peripheral T cells activated with phorbol myristic acetate and ionomycin also produced functional sFasL, suggesting that human sFasL works as a pathological agent in systemic tissue injury.
Fas ligand (FasL) is a 40 kDa type II membrane protein belonging to the tumor necrosis factor family, which induces apoptosis by binding to its receptor, Fas. In this report, we isolated the chromosomal gene for human FasL. The human FasL gene consists of approximately 8.0 kb and is split into four exons. The human FasL gene was mapped on chromosome 1q23 by in situ hybridization against human metaphase chromosomes. Human FasL cDNA was isolated by the reverse polymerase chain reaction of mRNA prepared from human activated peripheral blood lymphocytes. Human FasL is a type II membrane protein consisting of 281 amino acids with a calculated M(r) of 31,759. It has an identity of 76.9% at the amino acid sequence level with mouse FasL. Both human and mouse recombinant FasL expressed in COS induced apoptosis in the cells expressing either human Fas or mouse Fas, indicating that FasL fully cross-reacts between human and mouse. A comparison of human and mouse FasL chromosomal genes indicated that a approximately 300 bp sequence upstream of the ATG initiation codon is highly conserved between them. Several transcription cis-regulatory elements such as SP-1, NF-kappa B and IRF-1 were recognized in this region.
We study primordial gravitational waves produced during inflation in quantum gravity at a Lifshitz point proposed by Hořava. Assuming power-counting renormalizability, foliation preserving diffeomorphism invariance, and the condition of detailed balance, we show that primordial gravitational waves are circularly polarized due to parity violation. The chirality of primordial gravitational waves is a quite robust prediction of quantum gravity at a Lifshitz point which can be tested through observations of cosmic microwave background radiation and stochastic gravitational waves.
Secretin is a 27 amino acid peptide which stimulates the secretion of bicarbonate, enzymes and potassium ion from the pancreas. A complementary DNA encoding the rat secretin receptor was isolated from a CDM8 expression library of NG108‐15 cell line. The secretin receptor expressed in COS cells could specifically bind the iodinated secretin with high and low affinities. Co‐expression of the secretin receptor with the alpha‐subunit of rat Gs protein increased the concentration of the high affinity receptor in the membrane fraction of the transfected COS cells. Secretin could stimulate accumulation of cAMP in COS cells expressing the cloned secretin receptor. The nucleotide sequence analysis of the cDNA has revealed that the secretin receptor consists of 449 amino acids with a calculated Mr of 48,696. The secretin receptor contains seven putative transmembrane segments, and belongs to a family of the G protein‐coupled receptor. However, the amino acid sequence of the secretin receptor has no significant similarity with that of other G protein‐coupled receptors. A 2.5 kb mRNA coding for the secretin receptor could be detected in NG108‐15 cells, and rat heart, stomach and pancreatic tissue.
Although recent studies have reported that low-intensity resistance training with blood flow restriction could stress the muscle effectively and provide rapid muscle hypertrophy and strength gain equivalent to those of high-intensity resistance training, the exact mechanism and its generality have not yet been clarified. We investigated the intramuscular metabolism during low-intensity resistance exercise with blood flow restriction and compared it with that of high-intensity and low-intensity resistance exercises without blood flow restriction using (31)P-magnetic resonance spectroscopy. Twenty-six healthy subjects (22 +/- 4 yr) participated and performed unilateral plantar flexion (30 repetitions/min) for 2 min. Protocols were as follows: low-intensity exercise (L) using a load of 20% of one-repetition maximum (1 RM), L with blood flow restriction (LR), and high-intensity exercise using 65% 1 RM (H). Intramuscular phosphocreatine (PCr) and diprotonated phosphate (H(2)PO(4)(-)) levels and intramuscular pH at rest and during exercise were obtained. We found that the PCr depletion, the H(2)PO(4)(-) increase, and the intramuscular pH decrease during LR were significantly greater than those in L (P < 0.001); however, those in LR were significantly lower than those in H (P < 0.001). The recruitment of fast-twitch fiber evaluated by inorganic phosphate splitting occurred in only 31% of the subjects in LR, compared with 70% in H. In conclusion, the metabolic stress in skeletal muscle during low-intensity resistance exercise was significantly increased by applying blood flow restriction, but did not generally reach that during high-intensity resistance exercise. This new method of resistance training needs to be examined for optimization of the protocol to reach equivalence with high-intensity resistance training.
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