Root endophytic Penicillium promotes growth of Antarctic vascular plants by enhancing nitrogen mineralization

Fungal endophyte associations have been suggested as a possible strategy of Antarctic vascular plants for surviving the extreme environmental conditions of Antarctica. However, the mechanisms by which this occurs are still poorly understood. The role of root fungal endophytes in nitrogen mineralization and nutrient uptake, as well as their impact on the performance of Antarctic plants, were studied. We tested root endophytes, isolated from Colobanthus quitensis and Deschampsia antarctica, for lignocellulolytic enzyme production, nitrogen mineralization, and growth enhancement of their host plants. Penicillium chrysogenum and Penicillium brevicompactum were identified using a molecular approach as the main root endophytes inhabiting C. quitensis and D. antarctica, respectively. Both root endophytes were characterized as psychrophilic fungi displaying amylase, esterase, protease, cellulase, hemicellulase, phosphatase and urease enzymatic activities, mainly at 4 °C. Moreover, the rates and percentages of nitrogen mineralization, as well as the final total biomass, were significantly higher in symbiotic C. quitensis and D. antarctica individuals. Our findings suggest that root endophytes exert a pivotal ecological role based not only to breakdown different nutrient sources but also on accelerating nitrogen mineralization, improving nutrient acquisition, and therefore promoting plant growth in Antarctic terrestrial ecosystems.

     

Combined systemic and local delivery of stem cell inducing/recruiting factors for in situ tissue regeneration

Whereas the conventional tissue engineering strategy involves the use of scaffolds combined with appropriate cell types to restore normal functions, the concept of in situ tissue regeneration uses host responses to a target-specific scaffold to mobilize host cells to a site of injury without the need for cell seeding. For this purpose, local delivery of bioactive molecules from scaffolds has been generally used. However, this approach has limited stem cell recruitment into the implants. Thus, we developed a combination of systemic delivery of substance P (SP) and local release of stromal-derived factor-1α (SDF-1α) from an implant. In this study, we examined whether this combined system would significantly enhance recruitment of host stem cells into the implants. Flow cytometry and immunohistochemistry for CD29/CD45, CD146/α-smooth muscle actin, and c-kit demonstrated that this system significantly increased the number of stem cell-like cells within the implants when compared with other systems. In vitro culture of the cells that had infiltrated into the scaffolds from the combined system confirmed that host stem cells were recruited into these implants and indicated that they were capable of differentiation into multiple lineages. These results indicate that this combined system may lead to more efficient tissue regeneration.     

Departures from the physical optimality in the bronchial tree of rats (Rattus norvegicus)

We studied the departure from the physical optimality of the bronchial tree of rats using both i) the minimum volume and power and ii) the minimum surface and drag criteria, considering the bronchial junction as the unit study based on Zamir's model for vascular trees. Our results show deviations of the junctions of the bronchial tree from the expected optimums in the proximal airway that can be explained by both, the turbulent or transitional flow regime, and the airway's necessity to distribute its terminal branches in the alveolar surface filling the thoracic volume. The departures of the observed values at the optimum for the minimum volume and power were significantly different than the obtained departure values for the minimum surface and drag criteria. The departure from the optimum was directly related to the diameter of the smallest branch. The slopes of the regressions for the two criteria were different. The regression lines intercept at a bronchial diameter d2 = 0.129 mm. This result agreed with the idea that the tube diameter is limited at small values by the increasing flow resistance with decreasing tube diameter while at large values is limited by the increasing tube volume and dead space with increasing tube diameter.     

Modelling of growth conditions for cyanobacterium Spirulina platensis in microcosms

The influence of cultivation conditions on the growth of the cyanobacterium Spirulina platensis was investigated by using two types of photobioreactors. In a rotative photobioreactor the doubling time (t _d) was 3.54 days. The better value found for t _d in an aerated photobioreactor by changing the initial nitrogen concentration (NaNO₃) at 0.003, 0.015, 0.030 and 0.060M was 2.5 days. A factorial experimental design was performed in order to estimate the contributions of initial nitrogen concentration, inoculum and cultivation time as well as their interactions. All three factors and their interactions proved to be significant in influencing the cellular concentration of S. platensis.     

The Hydrostatic and Hydrodynamic Volumes of Polyols in Aqueous Solutions and Their Sweet Taste

The tastes and solution properties of sugar alcohols were studiedin an attempt to illuminate the mechanism of sweet taste chemoreception.The SMURF method was used to measure taste time-intensity ofaqueous solutions of sugar alcohols and the results were interpretedusing the Stevens power function and kinetic parameters. Theapparent molar volumes, apparent specific volumes, partial molarvolumes, partial specific volumes and intrinsic viscositiesof the solutions were studied. Apparent molar volume reflectsthe size of the molecule in a hydrostatic state whereas intrinsicviscosity gives a measure of the size of the molecules in ahydrodynamic state. Generally the apparent molar volumes ofthe polyols are 6–13% greater than those of the parentsugars, indicating less interaction with the water structure.Apparent specific volume values can predict taste quality, andthe average apparent specific volume for the sugar alcoholsstudied fits within the central part of the sweet range, i.e.0.5–0.68 cm³/g, which accords with their ability to elicita pure sweet taste response. Intensities and persistences ofsweetness in the polyols followed the same trend as intrinsicviscosities. Chem. Senses 22: 149–161, 1997.