Abstract. Non-isothermal crystallization and subsequent melting of three grades of ethylene-vinyl acetate copolymer were investigated by differential scanning calorimetry (DSC) technique. The DSC crystallization curves show that vinyl acetate (VAc) content has the same effect on the onset, peak and final crystallization temperatures, and these copolymers have almost the same spacing of thermal windows under identical crystallization condition. Subsequent melting DSC results suggest that EVA14 (14 wt% VAc) has the narrowest distribution of lamellar thickness and the most perfect crystals. Though the instantaneous nucleation was preferred, non-isothermal crystallization kinetics shows that EVA14 could form tridimensional crystallites, whereas EVA18 (18 wt% VAc) and EVA28 (28 wt% VAc) are prone to crystallize two-dimensionally, as a result of more noncrystallizable VAc co-monomers introduced in the crystallizable ethylene segments. The growth rate falls on the following sequence: EVA14>EVA18>EVA28. Moreover, the kinetic crystallizability G also well characterizes the variation of the non-isothermal crystallization of these EVA materials, in the view of structural impediment caused by the VAc content.

The c-Jun NH 2 -terminal protein kinase (JNK) is a mitogen-activated protein kinase (MAPK) involved in the regulation of various physiological processes. Its activity is increased upon phosphorylation by the MAPK kinases MKK4 and MKK7. The early embryonic death of mice lacking an mkk4 or mkk7 gene has provided genetic evidence that MKK4 and MKK7 have nonredundant functions in vivo. To elucidate the physiological role of MKK4, we generated a novel mouse model in which the mkk4 gene could be specifically deleted in the brain. At birth, the mutant mice were indistinguishable from their control littermates, but they stopped growing a few days later and died prematurely, displaying severe neurological defects. Decreased JNK activity in the absence of MKK4 correlated with impaired phosphorylation of a subset of physiologically relevant JNK substrates and with altered gene expression. These defects resulted in the misalignment of the Purkinje cells in the cerebellum and delayed radial migration in the cerebral cortex. Together, our data demonstrate for the first time that MKK4 is an essential activator of JNK required for the normal development of the brain.The c-Jun NH 2 -terminal protein kinase (JNK) (also called stress-activated protein kinase) is a member of the mitogenactivated protein kinase (MAPK) family, implicated in the regulation of numerous cellular functions in response to environmental stresses, growth factors, hormones, and proinflammatory cytokines (11). Three genes, jnk1, jnk2, and jnk3, encoding 10 isoforms, have been cloned. JNK1 and JNK2 are ubiquitously expressed, while JNK3 is almost exclusively found in the central nervous system (CNS). To understand the physiological functions of the JNK isoforms in vivo, transgenic mice deficient in one or more of the jnk genes have been studied (11). Their phenotypic analysis highlighted the importance of JNK-mediated apoptosis during the development of the CNS and in response to brain injury (26, 43, 52). However, apoptosis does not represent the only functional consequence of JNK activation. For example, JNK1 appears to contribute to establishing dendritic architecture in the brain (3,8,42).Analogous to other MAPKs, JNK is activated via the sequential activation of protein kinases, which include two dualspecificity MAPK kinases (MKK4 and MKK7) and multiple MAPK kinase kinases (MEKKs) (51). The MEKKs phosphorylate and activate MKK4 and MKK7, which, in turn activate JNK by dual phosphorylation on Thr and Tyr residues within a Thr-Pro-Tyr motif in protein kinase subdomain VIII (51). While MKK7 is a specific activator of JNK, MKK4 can also phosphorylate the Thr-Gly-Tyr motif of the p38 MAPK (50).Like JNK, p38 MAPK is activated in mammalian cells by various stress stimuli and proinflammatory cytokines (55). Physiological evidence for a role of MKK4 in activating the p38 MAPK cascade was recently provided by demonstrating that decreased expression of MKK4 due to small interfering RNA in mouse embryonic fibroblasts lacking both MKK3 and MKK6 suppressed stress-induc...

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In the search for biocompatible composite microspheres to be used as a hemostatic agent, in a previous study, we designed a novel biomaterial, consisting of composite microspheres containing three natural biological ingredients, carboxymethyl chitosan, sodium alginate and collagen (CSCM). Furthermore, the chemical and physical properties, hemostatic ability, biocompatibility and cytotoxicity were investigated in vitro. In this work, the in vivo hemostatic performance, wound healing, hemocompatibility, histocompatibility, and biodegradability were evaluated by a series of experiments. The results showed that CSCM could both stop bleeding and enhance healing efficiency by accelerating the clotting and the wound closure rate, suggesting that CSCM acts as a hemostat, and enhances wound healing. In addition, the CSCM material had negligible intracutaneous stimulation reactions and no obvious hemolytic reactions. More importantly, CSCM can be degraded in vivo without significant impacts on physiology, biochemistry, and organization. Thus, CSCM may be a useful tool to stop bleeding in emergency conditions in both military and civilian settings.