Processing and characterization of porous structures from chitosan and starch for tissue engineering scaffolds

Natural biodegradable polymers were processed by different techniques for the production of porous structures for tissue engineering scaffolds. Potato, corn, and sweet potato starches and chitosan, as well as blends of these, were characterized and used in the experiments. The techniques used to produce the porous structures included a novel solvent-exchange phase separation technique and the well-established thermally induced phase separation method. Characterization of the open pore structures was performed by measuring pore size distribution, density, and porosity of the samples. A wide range of pore structures ranging from 1 to 400 microm were obtained. The mechanisms of pore formation are discussed for starch and chitosan scaffolds. Pore morphology in starch scaffolds seemed to be determined by the initial freezing temperature/freezing rate, whereas in chitosan scaffolds the shape and size of pores may have been determined by the processing route used. The mechanical properties of the scaffolds were assessed by indentation tests, showing that the indentation collapse strength depends on the pore geometry and the material type. Bioactivity and degradation of the potential scaffolds were assessed by immersion in simulated body fluid.     

Systematic review of Atractus schach (Serpentes: Dipsadidae) species complex from the Guiana Shield with description of three new species

The Guiana Shield harbours one of the best preserved and largest extents of tropical forest on Earth and an immense biodiversity. The herpetofauna of this region remains poorly known. The species-rich snake genus Atractus contains ～140 species, many with complicated taxonomic histories, including A. schach. Examination of specimens in museums and newly collected material from French Guiana has allowed the illustration of hemipenial morphology for the first time and an expanded diagnosis. Concatenated molecular phylogenetic (mitochondrial and nuclear genes) and phenotypic (morphometrics, external and hemipenial morphology) analyses confirm non-monophyly of the A. flammigerus group and indicate that A. schach is a species complex with three new species described here. The geographic distribution of A. schach sensu stricto is restricted to Guiana, Surinam, and French Guiana north of Tumucumaque massif. Populations tentatively assigned to A. schach from the east from French Guiana in the Roura lowlands to Almeirim, and from central Amazonia between the Negro and Trombetas rivers in Brazil are also recognized as new species. Our results suggest that populations from south of the Amazon River are not conspecific with those from the Guiana Shield.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:A7AE40BC-4716-4302-B3BE-1F43600B0A72     

Increase in the ability of human cancer cells to induce cytotoxic T lymphocytes by ultraviolet irradiation

The roles of ultraviolet-B (UV) radiation in the immunogenicity of human cancer cells have not been fully studied. We have investigated the effects of UV radiation on metastatic melanoma and renal cell carcinoma cells with regard to MHC antigen expression and the ability to induce cytotoxic T lymphocyte (CTL) activity in peripheral blood mononuclear cells (PBMC) or tumor-infiltrating lymphocytes (TIL) against untreated autologous tumor cells. UV radiation respectively decreased or increased MHC class I expression of freshly isolated tumor cells or cultured tumor cells, and also decreased MHC class I expression of starved cultured tumor cells. It increased the ability of both freshly isolated and cultured tumor cells to induce CTL activity from PBMC against untreated autologous tumor cells. UV-irradiated subclones that were more susceptible to CTL lysis were more potent for CTL induction from TIL than either an untreated parental clone or a UV-irradiated subclone that was resistant to CTL lysis. In summary, UV radiation increased the ability of tumor cells to induce CTL activity without a corresponding effect on MHC antigen expression.This work was supported in part by a grant CA47891 from the National Cancer Institute, USA, a grant-in-aid of the comprehensive 10-years strategy for cancer control from ministry of a Health and Welfare, Japan, and the Ishibashi Research Fund, Japan     

Outer pore topology of the ECaC-TRPV5 channel by cysteine scan mutagenesis

The substituted cysteine accessibility method (SCAM) was used to map the external vestibule and the pore region of the ECaC-TRPV5 calcium-selective channel. Cysteine residues were introduced at 44 positions from the end of S5 (Glu515) to the beginning of S6 (Ala560). Covalent modification by positively charged MTSET applied from the external medium significantly inhibited whole cell currents at 15/44 positions. Strongest inhibition was observed in the S5-linker to pore region (L520C, G521C, and E522C) with either MTSET or MTSES suggesting that these residues were accessible from the external medium. In contrast, the pattern of covalent modification by MTSET for residues between Pro527 and Ile541 was compatible with the presence of a alpha-helix. The absence of modification by the negatively charged MTSES in that region suggests that the pore region has been optimized to favor the entrance of positively charged ions. Cysteine mutants at positions -1, 0, +1, +2 around Asp542 (high Ca2+ affinity site) were non-functional. Whole cell currents of cysteine mutants at +4 and +5 positions were however covalently inhibited by external MTSET and MTSES. Altogether, the pattern of covalent modification by MTS reagents globally supports a KcsA homology-based three-dimensional model whereby the external vestibule in ECaC-TRPV5 encompasses three structural domains consisting of a coiled structure (Glu515 to Tyr526) connected to a small helical segment of 15 amino acids (527PTALFSTFELFLT539) followed by two distinct coiled structures Ile540-Pro544 (selectivity filter) and Ala545-Ile557 before the beginning of S6.     

新疆马鹿塔里木亚种的现状与保护

新疆马鹿塔里木亚种高度适应荒漠生境, 自20 世纪50 年代以来, 由于自然和人为因素的影响, 种群数量急剧下降。栖息地退缩和片段化不仅导致种群遗传多样性的丧失, 而且也因遗传漂变和近亲繁殖, 不断地加剧了该亚种的濒危程度。为有效的保护该物种, 特提出可行的保护措施建议。     

Antidepressant-like effect of a Ginkgo biloba extract (EGb761) in the mouse forced swimming test: role of oxidative stress

EGb761 is a well-defined mixture of active compounds extracted from Ginkgo biloba leaves. This extract is used clinically due to its neuroprotective effects, exerted probably via its potent antioxidant or free radical scavenger action. Previous studies suggest that oxidative stress, via free radical production, may play an important role in depression and animal models for depression-like behavior. Preclinical studies have suggested that antioxidants may have antidepressants properties. The aim of this study was to investigate the antidepressant-like of EGb761 due to its antioxidant role against oxidative stress induced in the forced swimming test, the most widely used preclinical model for assessing antidepressant-like behavior. Male BALB/c mice were pretreated with EGb761 (10 mg/kg, ip) daily for 17 days followed by the forced swimming test and spontaneous locomotor activity. Animals were sacrificed to evaluate lipid peroxidation, different antioxidant enzyme activities, serotonin and dopamine content in midbrain, hippocampus and prefrontal cortex. EGb761 significantly decreased the immobility time (39%) in the forced swimming test. This antidepressant-like effect of EGb761 was associated with a reduction in lipid peroxidation and superoxide radical production (indicated by a downregulation of Mn-superoxide dismutase activity), both of which are indicators of oxidative stress. The protective effect of EGb761 is not related to excitatory or inhibitory effects in locomotor activity, and was also associated with the modulation of serotonergic and dopaminergic neurotransmission. It is suggested that EGb761 produces an antidepressant-like effect, and that an antioxidant effect against oxidative stress may be partly responsible for its observed neuroprotective effects.     

Molecular insights into the klotho-dependent, endocrine mode of action of fibroblast growth factor 19 subfamily members

Unique among fibroblast growth factors (FGFs), FGF19, -21, and -23 act in an endocrine fashion to regulate energy, bile acid, glucose, lipid, phosphate, and vitamin D homeostasis. These FGFs require the presence of Klotho/betaKlotho in their target tissues. Here, we present the crystal structures of FGF19 alone and FGF23 in complex with sucrose octasulfate, a disaccharide chemically related to heparin. The conformation of the heparin-binding region between beta strands 10 and 12 in FGF19 and FGF23 diverges completely from the common conformation adopted by paracrine-acting FGFs. A cleft between this region and the beta1-beta2 loop, the other heparin-binding region, precludes direct interaction between heparin/heparan sulfate and backbone atoms of FGF19/23. This reduces the heparin-binding affinity of these ligands and confers endocrine function. Klotho/betaKlotho have evolved as a compensatory mechanism for the poor ability of heparin/heparan sulfate to promote binding of FGF19, -21, and -23 to their cognate receptors.