Training effect and fatigue in polypyrrole-based artificial muscles

Artificial muscles based on an electrochemomechanical strain (ECMS) in conducting polymers, namely polypyrrole (PPy) film, have been studied from viewpoints of training, fatigue and aging by repeat cycles under tensile loads. ECMS was approximately 2% in a saline solution, resulting from both insertion and exclusion of Na(+) with solvated water molecules as well in the film. Transient responses of ECMS and current induced by voltage stimuli were measured under tensile stresses up to 5 MPa to see the training effect, fatigue and aging of the film. At higher stresses the film showed larger creeping, which resulted from realignment or conformation change, slipping and breaking of polymer chains. After the experience of large stresses, the training effect in ECMS was appreciably observed as an increase of the strain. Without stress the conductivity of the film was stable (no fatigue) upon an electrochemical cycle; however, under high tensile stresses the conductivity decreased remarkably (fatigue and aging). It is to be noted that straightened polymer chains can be easily oxidized and degraded due to lower pi-electron energy. The conversion efficiency from electrical to mechanical energy in this system was found to be less than 0.03%.     

High resolution bands in maize chromosomes by G-banding methods

Summary It was demonstrated that G-bands are unequivocally present in plant chromosomes, in contrast to what had been formerly believed by plant cytologists. Maize chromosomes prepared by an enzymatic maceration method and treated with trypsin or SDS showed clear G-bands spreading along the chromosomes. The most critical point during the G-banding procedures was the post-fixation with glutaraldehyde solution. Banding patterns were processed by using the chromosome image analyzing system and a clearer image was obtained. Gbanding technique and the image manipulation method described here can be applied to many plant species, and would contribute new information in the field of plant cytology and genetics.     

Proliferation of both somatic and germ cells is affected in the Drosophila mutants of raf proto-oncogene.

The genomic and cDNA fragments of Drosophila melanogaster, homologous to human c-raf-1, were cloned. The nucleotide sequence predicted the primary structure of a polypeptide of 666 amino acid residues with a highly conserved Ser-Thr kinase domain on its carboxy terminal half. Draf-1 was mapped to the 2F region of the X chromosome. Two newly induced recessive lethals belonging to a complementation group in this region were identified to be defective in Draf-1 by P element-mediated rescue experiments. The mutants die at larval/pupal stages. The mutant larvae are apparently normal, but they harbor serious defects in the organs containing proliferating cells of both somatic and germ line origins. Maternal effects on embryogenesis indicated that Draf-1 is also required in early larval development.     

Parabolic flight experiments on physiological data acquisition and processing technologies using small jet aircraft (MU300)

The parabolic aircraft flight provides a short low gravity environment for approximately 20 seconds, which may not be sufficient for a research on the physiological phenomenon induced by actual weightlessness in space. However, the method is still useful to reveal essential and characteristic feature of physiological signs, and is available for testing hardware and also training of crew member during altered gravity. This paper reports the summary of parabolic flight experiments recently conducted as a NASDA program (1990-1992). The program is providing opportunities in low gravity research with small jet aircraft for researchers and agencies. The flight experiments in the life science area have been conducted mostly focused on a physiological changes and basic methodology which may be effective under the altered gravity condition. In this study, the following research team, NASDA, Research Institute of Environmental Medicine, Nagoya University, Toyohashi University of Technology, Tokyo Metropolitan Hospital, Torey Research Center and JSUP were involved and coordinated for the research.     

Effect of diabetes on aortic nitric oxide synthesis in spontaneously hypertensive rats; does captopril modulate this effect?

Nitric oxide (NO) is a potent regulator in the cardiovascular system; it is generated by the nitric oxide synthase (NOS) family of proteins. NO produced in endothelial cells plays a crucial role in vascular functions. The aim of this study was to clarify the effect of diabetes on aortic NO synthesis in a model of genetic hypertension and determine whether captopril modulates this effect. Diabetes was induced in ten weeks old spontaneously hypertensive rats (SHR) by streptozotocin injection. The rats were allocated into 3 groups: control group 1, non-diabetic SHR; group 2, diabetic SHR; group 3, diabetic SHR group receiving captopril at 80 mg/kg in drinking water for 4 weeks. Mean blood pressure (MBP) was measured once a week by tail-cuff method. Aortic NO metabolities (nitrite/nitrate) and endothelial NOS (NOS-3) were assayed by Griess reaction and by immunoblotting and immunohistochemistry, respectively. There was a significant decrease in nitrite/nitrate (NOx) in aortas of diabetic SHR compared with controls. The decrease of aortic NOx in diabetic SHR was accompanied by a decrease in NOS-3 expression. Captopril treatment reduced MBP without affecting either NOx level or NOS-3 expression in aortas of diabetic SHR. We conclude that STZ-induced diabetes decreased NO in aortas of SHR that may reflect endothelial cell dysfunction; captopril administration decreased MBP without affecting NO level in aortas of diabetic SHR which suggest that the blood pressure-lowering effects of captopril were independent of NO.     

Sulfonylurea as well as elevated glucose levels stimulate reactive oxygen species production in the pancreatic beta-cell line, MIN6-a role of NAD(P)H oxidase in beta-cells

Increased oxidative stress may play a key role in the progressive deterioration of pancreatic beta-cells and the development of diabetes. However, the underlying mechanism is not well understood. Exposure of pancreatic beta-cell line, MIN6 cells, to elevated glucose level for 2h induced an increase in reactive oxygen species (ROS) production, as evaluated by the staining of 2',7'-dichlorofluorescein diacetate. This effect was completely blocked by NAD(P)H oxidase inhibitor (diphenylene iodonium) and protein kinase C (PKC) inhibitor (calphostin C), but not affected by other flavoprotein inhibitors (rotenone, oxypurinol, or l-N-monomethyl arginine). Glibenclamide also stimulated ROS production in a dose-dependent manner. This effect was again blocked by diphenylene iodonium and calphostin C. In conclusion, insulin secretagogues, both glibenclamide and elevated glucose level, stimulated ROS production in beta-cells through a PKC-dependent activation of NAD(P)H oxidase. This mechanism may be a novel therapeutic target for preventing the progression of beta-cell deterioration.     

Expression and Function of Allergin-1 on Human Primary Mast Cells

Mast cells (MC) play an important role in allergic and non-allergic immune responses. Activation of human MC is modulated by several cell surface inhibitory receptors, including recently identified Allergin-1 expressed on both human and mouse MC. Although Allergin-1 suppresses IgE-mediated, mast cell–dependent anaphylaxis in mice, the expression profile and function of Allergin-1 on human primary MC remains undetermined. Here, we established a seven-color flow cytometry method for assessing expression and function of a very small number of human primary MC. We show that Allergin-1S1, a splicing isoform of Allergin-1, is predominantly expressed on human primary MC in both bronchoalveolar lavage (BAL) fluid and nasal scratching specimens. Moreover, Allergin-1S1 inhibits IgE-mediated activation from human primary MC in BAL fluid. These results indicate that Allergin-1 on human primary MC exhibits similar characteristics as mouse Allergin-1 in the expression profile and function.     

Structural Basis for Ubiquitin Recognition by Ubiquitin-Binding Zinc Finger of FAAP20

Several ubiquitin-binding zinc fingers (UBZs) have been reported to preferentially bind K63-linked ubiquitin chains. In particular, the UBZ domain of FAAP20 (FAAP20-UBZ), a member of the Fanconi anemia core complex, seems to recognize K63-linked ubiquitin chains, in order to recruit the complex to DNA interstrand crosslinks and mediate DNA repair. By contrast, it is reported that the attachment of a single ubiquitin to Rev1, a translesion DNA polymerase, increases binding of Rev1 to FAAP20. To clarify the specificity of FAAP20-UBZ, we determined the crystal structure of FAAP20-UBZ in complex with K63-linked diubiquitin at 1.9 Å resolution. In this structure, FAAP20-UBZ interacts only with one of the two ubiquitin moieties. Consistently, binding assays using surface plasmon resonance spectrometry showed that FAAP20-UBZ binds ubiquitin and M1-, K48- and K63-linked diubiquitin chains with similar affinities. Residues in the vicinity of Ala168 within the α-helix and the C-terminal Trp180 interact with the canonical Ile44-centered hydrophobic patch of ubiquitin. Asp164 within the α-helix and the C-terminal loop mediate a hydrogen bond network, which reinforces ubiquitin-binding of FAAP20-UBZ. Mutations of the ubiquitin-interacting residues disrupted binding to ubiquitin in vitro and abolished the accumulation of FAAP20 to DNA damage sites in vivo. Finally, structural comparison among FAAP20-UBZ, WRNIP1-UBZ and RAD18-UBZ revealed distinct modes of ubiquitin binding. UBZ family proteins could be divided into at least three classes, according to their ubiquitin-binding modes.     

RanGTP and the actin cytoskeleton keep paternal and maternal chromosomes apart during fertilization

Zygotes require two accurate sets of parental chromosomes, one each from the mother and the father, to undergo normal embryogenesis. However, upon egg–sperm fusion in vertebrates, the zygote has three sets of chromosomes, one from the sperm and two from the egg. The zygote therefore eliminates one set of maternal chromosomes (but not the paternal chromosomes) into the polar body through meiosis, but how the paternal chromosomes are protected from maternal meiosis has been unclear. Here we report that RanGTP and F-actin dynamics prevent egg–sperm fusion in proximity to maternal chromosomes. RanGTP prevents the localization of Juno and CD9, egg membrane proteins that mediate sperm fusion, at the cell surface in proximity to maternal chromosomes. Following egg–sperm fusion, F-actin keeps paternal chromosomes away from maternal chromosomes. Disruption of these mechanisms causes the elimination of paternal chromosomes during maternal meiosis. This study reveals a novel critical mechanism that prevents aneuploidy in zygotes.     

Molecular design, synthesis and bioactivity of glycosyl hydrazine and hydrazone derivatives: notable effects of the sugar moiety

Assuming that the water solubility of our previous hydrazone derivatives would improve after modification with sugars while keeping or modulating their notable biological activities, we designed and synthesized some glycosyl hydrazine and hydrazone derivatives. Bioassay results indicated that the antitumor activity of our previously prepared hydrazones reduced or disappeared after modification with sugars. On the contrary, some glycosyl derivatives displayed much better antifungal activity against selected fungi. Obviously, a small sugar can change the biological activity of hydrazones significantly.