Summary: A double comb‐shaped water soluble copolymer, poly[poly(ethylene oxide) methyl ether methacrylate]‐block‐poly(N‐isopropylacrylamide)‐block‐poly[poly (ethylene oxide) methyl ether methacrylate], abbreviated as [P(MA‐MPEO)‐block‐PNIPAM‐block‐P(MA‐MPEO)], with a controlled molecular weight and narrow polydispersity was successively synthesized using a macromonomer technique. The 60Co γ irradiation polymerization of MA‐MPEO in the presence of dibenzyl trithiocarbonate (DBTTC) at room temperature afforded a polymer, P(MA‐MPEO)‐SC(S)S‐P(MA‐MPEO), which was subsequently used as a macro RAFT agent in the RAFT polymerization of N‐isopropylacrylamide, and water soluble double comb‐shaped copolymers, P(MA‐MPEO)‐block‐PNIPAM‐block‐P(MA‐MPEO), were successfully obtained.
Structure of the double comb‐shaped copolymer. 相似文献
BACKGROUND: Bone morphogenetic protein-15 (BMP-15) has been shown to influence oocyte maturation and quality. However, no relationship has been established between BMP-15 and oocyte quality/embryonic development in humans. The aim of this study is to investigate BMP-15 level in human follicular fluid (FF) and its possible role in determining oocyte quality and developmental potential. METHODS: A total of 79 oocytes and their corresponding FF from 79 women undergoing ICSI were examined. Individual oocytes were inseminated and subsequently assessed on the basis of their fertilization, cleavage and preimplantation development. BMP-15, FSH, estradiol (E(2)) and progesterone levels of FF were also analysed via the techniques of western blot or radioimmunoassay. RESULTS: Higher FF BMP-15 levels were observed in the fertilized and cleaved groups versus the unfertilized and uncleaved groups, respectively (P < 0.05). The best (Grade I) embryo morphology was associated with higher FF BMP-15 levels than Grade II or III embryos (P < 0.01). A significant positive correlation was found between BMP-15 and E(2) levels in the same follicle. CONCLUSION: The present study demonstrates that the BMP-15 level in FF appears to be a potential factor in predicting oocyte quality and subsequent embryo development, and is correlated with E(2) level, which may additionally be a valuable predictor of oocyte fertilization. 相似文献
We hypothesized that epidural spinal cord stimulation (ES) and quipazine (a serotonergic agonist) modulates the excitability of flexor and extensor related intraspinal neural networks in qualitatively unique, but complementary, ways to facilitate locomotion in spinal cord-injured rats. To test this hypothesis, we stimulated (40 Hz) the S(1) spinal segment before and after quipazine administration (0.3 mg/kg, ip) in bipedally step-trained and nontrained, adult, complete spinal (mid-thoracic) rats. The stepping pattern of these rats was compared with control rats. At the stimulation levels used, stepping was elicited only when the hindlimbs were placed on a moving treadmill. In nontrained rats, the stepping induced by ES and quipazine administration was non-weight bearing, and the cycle period was shorter than in controls. In contrast, the stepping induced by ES and quipazine in step-trained rats was highly coordinated with clear plantar foot placement and partial weight bearing. The effect of ES and quipazine on EMG burst amplitude and duration was greater in flexor than extensor motor pools. Using fast Fourier transformation analysis of EMG bursts during ES, we observed one dominant peak at 40 Hz in the medial gastrocnemius (ankle extensor), whereas there was less of dominant spectral peak in the tibialis anterior (ankle flexor). We suggest that these frequency distributions reflect amplitude modulation of predominantly monosynaptic potentials in the extensor and predominantly polysynaptic pathways in the flexor muscle. Quipazine potentiated the amplitude of these responses. The data suggest that there are fundamental differences in the circuitry that generates flexion and extension during locomotion. 相似文献
