Fabrication of biodegradable poly(ester-amide)s based on tyrosine natural amino acid

N,N′-Bis[2-(methyl-3-(4-hydroxyphenyl)propanoate)]isophthaldiamide (5), a novel diol monomer containing chiral group, was prepared by the reaction of S-tyrosine methyl ester (3) with isophthaloyl dichloride (4a). A new family of optically active and potentially biodegradable poly(ester-amide)s (PEAs) based on tyrosine amino acid were prepared by the polycondensation reaction of diol monomer 5 with several aromatic diacid chlorides. The resulting new polymers were obtained in good yields with inherent viscosities ranging between 0.25 and 0.42 dL/g and are soluble in polar aprotic solvents. They showed good thermal stability and high optical purity. The synthetic compounds were characterized and studied by FT-IR, ¹H-NMR, specific rotation, elemental and thermogravimetric analysis (TGA) techniques and typical ones by ¹³C-NMR, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) analysis. Soil burial test of the diphenolic monomer 5, and obtained PEA6a, and soil enzymatic assay showed that the synthesized diol and its polymer are biologically active and probably biodegradable in soil environment.     

The effects of early and adult social environment on zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>) behavior

Because early social experience can have a profound effect on later mate and social choices, the availability of options and decisions made early in development can have major effects on adult behavior. Herein, we use strain differences among zebrafish, Danio rerio, as an experimental tool to test the effects of social experience on behavior. By manipulating the strain composition of groups in which the subject fish are housed at different ages, we tested (1) whether mixing with dissimilar individuals influenced subsequent behavior, (2) whether prolonged mixing during the juvenile stage had a more pronounced effect than a shorter period of mixing during adulthood and (3) whether mixing had a lasting effect after animals were resorted into groups of same strain animals. We found that social experience had a profound impact on social behavior. Both Nadia and TM1 individuals engaged in more frequent biting after having been in mixed strain groups compared to pure strain groups. This was true of groups mixed as juveniles, as well as adults, indicating that this response was not dependent on exposure during a critical developmental period. Also, TM1 fish (but not Nadia) having recently been housed in mixed-strain groups were more willing to leave the immediate vicinity of a shoal than were TM1 fish raised in pure strain groups. This change was more pronounced in groups mixed as juveniles than as adults. In addition, the observed changes persisted after mixed groups were separated into pure strain groups for a month. Other behavioral measures including Activity Level, Predator Response and Stress Recovery were unaffected by previous social experience.     

Effect of blending lignin biopolymer on the biodegradability of polyolefin plastics

The ability of the lignin-degrading microorganism Phanerochaete chrysosporium to attack polyethylene and polypropylene was investigated using a series of polymer blends containing 10, 20 and 30% lignin obtained from the waste product of pulp and paper industry. In the cultivation medium, lignin peroxidase and Mn(II)peroxidase activities were detected. Degradation was verified by quantitative u.v. spectrophotometric analysis of the cultivation medium and by liberation of CO₂ from the blends. Measurement of the tensile strength after 30-days cultivation showed that the mechanical properties of the polymer blends were decreased during the biodegradation process. The isolation of oligomer fractions by tetrahydrofuran (THF) extraction of biodegraded polymers and their characterization by gel permeation chromatography (GPC), u.v. and Fourier transmission infrared (FTIR) spectroscopy indicates that biotransformation of the lignin component during the cultivation process initiates partial biodegradation of the synthetic polymer matrix.     

Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement

The considerable therapeutic potential of human multipotent mesenchymal stromal cells (MSC) has generated markedly increasing interest in a wide variety of biomedical disciplines. However, investigators report studies of MSC using different methods of isolation and expansion, and different approaches to characterizing the cells. Thus it is increasingly difficult to compare and contrast study outcomes, which hinders progress in the field. To begin to address this issue, the Mesenchymal and Tissue Stem Cell Committee of the International Society for Cellular Therapy proposes minimal criteria to define human MSC. First, MSC must be plastic-adherent when maintained in standard culture conditions. Second, MSC must express CD105, CD73 and CD90, and lack expression of CD45, CD34, CD14 or CD11b, CD79alpha or CD19 and HLA-DR surface molecules. Third, MSC must differentiate to osteoblasts, adipocytes and chondroblasts in vitro. While these criteria will probably require modification as new knowledge unfolds, we believe this minimal set of standard criteria will foster a more uniform characterization of MSC and facilitate the exchange of data among investigators.     

Effects of Passage Through Tamarin Guts on the Germination Potential of Dispersed Seeds

Passage through tamarin guts may have an effect on seed germination potential. To examine these effects, and the variation between 2 sympatric tamarin species, we studied Saguinus mystax and S. fuscicollis in northeastern Peruvian Amazonia. For most of 39 plant species, neither germination success nor latency was modified by gut passage. Neutral effects on seed germination potential suggest that tamarins may fulfill criteria for effective seed dispersal.