Life cycle assessment of a geopolymer mixture for fireproofing applications

The International Journal of Life Cycle Assessment - Alkali-activated materials, also known as geopolymers, are considered promising assets in the sustainable materials industry. Given the...     

Thresholds for macroparasite infections

We analyse here the equilibria of an infinite system of partial differential equations modelling the dynamics of a population infected by macroparasites. We find that it is possible to define a reproduction number R₀ that satisfies the intuitive definition, and yields a sharp threshold in the behaviour of the system: if R₀ < 1, the parasite-free equilibrium (PFE) is asymptotically stable and there are no endemic equilibria; if R₀ > 1, the PFE is unstable and there exists a unique endemic equilibrium. The results mainly confirm what had been obtained in simplified models, except for the fact that no backward bifurcation occurs in this model. The stability of equilibria is established by extending an abstract linearization principle and by analysing the spectra of appropriate operators.Revised version: 14 November 2003Supported in part by CNR under Grant n. 00.0142.ST74 Metodi e modelli matematici nello studio dei fenomeni biologici     

Influence of beta-carotene on lysosomal hydrolases and their natural substrates in major salivary glands of hamsters treated with 7,12-dimethylbenzanthracene (DMBA)

We evaluated the effects of beta-carotene, a precursor of vitamin A, on the activity of some lysosomal hydrolases and on the levels of their natural substrates in hamster major salivary glands during experimental oral 7,12-dimethylbenzanthracene (DMBA) carcinogenesis. Sixty-four hamsters (Cricetus auratus) were divided into four groups--group 1: untreated control; group 2: DMBA was painted three times a week in the left buccal pouch; group 3: beta-carotene was painted three times a week in the left buccal pouch; group 4: DMBA and beta-carotene were painted alternatively in the left buccal pouch. After 16 weeks, the animals were sacrificed and the activities of some lysosomal hydrolases and their natural substrates in the major salivary glands were measured. beta-Carotene when administered topically in DMBA treated animals (group 4) reduced the levels of the majority of enzymes and substrates closer to those of the untreated control group, thus outlining a mild protective effect of beta-carotene towards the DMBA carcinogenic stress. Nevertheless, the presence of some enzymes which responded negatively to the combined administration of DMBA and beta-carotene suggests the necessity for future studies on the effect of beta-carotene at different concentrations, the systemic administration and the possibility to combine the topical beta-carotene administration with other chemopreventive drugs.     

Synthesis, pharmacological evaluation, and structure-activity relationships of benzopyran derivatives with potent SERM activity

The synthesis, binding affinity for estrogen receptor subtypes (ER alpha and ER beta) and pharmacological activity on rat uterus of a new class of potent ligands, characterized by a 3-phenylbenzopyran scaffold with a basic side chain in position 4, are reported. Some of these compounds, endowed with very high receptor affinity, showed potent inhibition of agonist-stimulated uterine growth, with no or limited proliferative effect. Binding affinity mostly depended on the nature and position of substituents at the 3-phenyl ring, while the uterine activity seems to be affected by basic chain length. Compound 9c (CHF4227) showed excellent binding affinity and antagonist activity on the uterus. The docking of benzopyran derivatives explained the structure-affinity relationships observed for 3-phenyl substitution: a small, hydrophobic 4'-substituent could interact with a small accessory binding cavity, while di-substitution at 4' and 3' led to some ER alpha selectivity. This selectivity can be ascribed to differences in amino acid composition and side chain conformation in the region accommodating the 3-phenyl ring at human ER alpha and ER beta ligand-binding domain.     

Bioactive recombinant neuregulin-1, -2, and -3 expressed in Escherichia coli

The neuregulins (NRGs) are a family of signaling proteins that are ligands for receptor tyrosine kinase of the ErbB family (namely ErbB3 and ErbB4). To date, four different neuregulin genes have been identified (neuregulin1-4). While NRG1 isoforms have been extensively studied, little is yet known about the other genes of the family. We report the expression of recombinant NRG1beta1, NRG2alpha, NRG2beta, and NRG3 as recombinant fusion proteins in Escherichia coli. The cDNA encoding for the EGF-like domain of each protein was cloned from the mouse olfactory bulb and inserted into the pET-19b vector allowing for bacterial expression of the protein fused to an N-terminal His tag. The recombinant NRGs expressed in the inclusion bodies were solubilized under denaturing conditions, purified by affinity chromatography, and refolded via dialysis in the presence of reducing agents. Purified recombinant NRGs were active as they bound to their receptors and induced their phosphorylation. In particular, and in agreement with data on the native proteins, all the molecules were able to bind and activate ErbB4 while only the rNRG1 and the two rNRG2 (but not rNRG3) bound ErbB3.     

Nuclear localization of the tight junction protein ZO-2 in epithelial cells

The tight junction constitutes the major barrier to solute and water flow through the paracellular space of epithelia and endothelia. It is formed by transmembrane proteins and submembranous molecules such as the MAGUKs ZOs. We have previously found that several MAGUKs, including those of the tight (ZO-1, ZO-2, and ZO-3) and septate junction (tamou and Dlg), contain one or two nuclear sorting signals located at their first PDZ and GK domains. Now we show that these proteins also contain a nuclear export signal and focus our study on the nuclear membrane shuttling of ZO-2. In sparse cultures this molecule concentrates at the nucleus in clusters, where it partially colocalizes with splicing factor SC35. Nuclear staining diminishes as the monolayer acquires confluence through a process sensitive to the nuclear export inhibitor leptomycin B. Nuclear localization can be induced by impairing cell-cell contacts, by mechanical injury. ZO-2 that shuttles from the cell periphery into the nucleus is not newly synthesized but originates from a preexistent pool. The movement of this protein is mediated by the actin cytoskeleton.     

Differences in the activity and distribution of peroxidases from three different portions of germinating Brassica oleracea seeds

Peroxidase (POD, EC 1.11.1.7) activity, cellular localization and isozyme patterns were investigated in the seed integument, cotyledon and embryo axis of Brassica oleracea cv. Cappuccio during pregermination and seedling growth. Seeds started to germinate after 24 h of imbibition. POD activity was localized in the pigmented layer of the integument and in procambial strands of the cotyledon and embryo axis in the first 24 h of imbibition. It was localized in the integumental cells of palisade, pigmented and aleurone layers and in epidermal, meristematic, procambial cells and xylem elements of the root and hypocotyl after 48 h of imbibition. POD activity increased during germination and early seedling growth: in the integument, it reached a maximum value after 72 h of imbibition, in the embryo axis and cotyledons, it increased up to 144 h of imbibition. The increase in peroxidase activity was accompanied by the appearance of new isozymes correlated with the development of seedling tissues. The isozyme profile was characterized by nine peroxidases: isoperoxidase of 50 kDa peculiar to integuments, that of 150 kDa to cotyledons and that of 82 kDa to the embryo axis. During pregerminative phase isozymes of 84 kDa were detected in the integument and cotyledons, of 48.5 kDa in the embryo axis. After germination, peroxidase activity and the complexity of the isozyme pattern increased, suggesting that they play a relevant role after rupture of the integument.