Biomass production of the mycorrhizal fungus Suillus grevillei: effect of pH and ammonium

The ability of the ectomycorrhizal fungus Suillus grevillei (Klotzsch) Singer to grow in agitated submerged culture was investigated by employing the Marx-Melin-Norkrans (MMN) medium. The operating conditions suitable for improving the biomass production were determined. Batch experimental tests were carried out in either shake flasks or a stirred tank reactor. The results showed that at least two factors strongly affected the fungal growth, namely the pH and the ammonia-nitrogen concentration in the medium. By controlling the acidity in the pH range 4-5 with a Na-citrate buffer solution and introducing the ammonia-nitrogen in a step-feed way (without exceeding a concentration of approximately 0.07 kg N/m3), the exponential growth phase continued for longer than that of the control culture (no stationary phase seemed to be reached after 17 days) and an approximately 2-fold increase of the biomass/substrate growth yield was obtained compared with the control culture.     

Macro approach and fuzzy modeling of entrapped biocatalyst

The interactions between a strain of Saccharomyces cerevisiae and an alginate matrix are investigated to ascertain the main factors affecting the bioreaction evolution. During the tests several parameters (glucose, ethanol, calcium ion and biomass concentration, pH, and alginate bed diameter) were evaluated, coupled with microscopic investigation inside the beads to determine the spatial biomass distribution. A detailed analysis of macro parameters and a correlation among them are proposed using a fuzzy algorithm. A global two-step fuzzy model results in which biomass distribution inside the beads is represented as a hidden parameter.     

Effect of dietary alpha-tocopheryl acetate and ascorbic acid on rabbit semen stored at 5 degrees C

The objective of this research was to verify the effects of dietary alpha-tocopheryl acetate (50 vs. 200 mg/kg diet) and ascorbic acid (0 vs. 1 g/L water) on the relative amounts on semen and motion characteristics, oxidative stability and fertilizing ability of rabbit spermatozoa stored for 24 h at 5 degrees C. A high amount of dietary (alpha-tocopheryl acetate significantly increased the level of Vitamin E in the semen (0.90 vs. 0.41 micromol/L) and its oxidative stability after storage (Thiobarbituric Acid Reactive Substances-- TBARS 15.88 vs. 20.90 nmol Malondialdehyde--MDA/mL). Ascorbic acid showed a different effect in relation to the Vitamin E status of animals: when associated with the higher level of Vitamin E it increased the (alpha-tocopherol and the oxidative stability of semen (2.67 micromol/L and 12.25 nmol MDA/mL, respectively), whereas both parameters were reduced with lower Vitamin E (0.13 micromol/L and 21.20 nmol MDA/mL). Semen traits were not modified by the separate supplementation of supranutritional levels of vitamins, whereas their combination significantly improved the viability and the kinetics of spermatozoa (e.g. track speed: 95.13 vs. 71.31 microm sec(-1)) with an increase in fertility rate (70.0 vs. 63.3; P=0.06) that could be considered almost significant.     

Relative quantification of chrysanthemum yellows (16Sr I) phytoplasma in its plant and insect host using real-time polymerase chain reaction

A real-time polymerase chain reaction (PCR) method for the quantification of chrysanthemum yellows (CY) phytoplasma DNA in its plant (Chrysanthemum carinatum) and insect (Macrosteles quadripunctulatus) host is described. The quantity of CY DNA was measured in each run relative to the amount of host DNA in the sample. Primers and a TaqMan probe for the specific PCR amplification of phytoplasma DNA were designed on a cloned CY-specific ribosomal fragment. Primers and TaqMan probes were also designed on sequences of the internal transcribed spacer region of the insect’s ITS1 rDNA and of the plant’s 18S rDNA for amplification from C. carinatum and M. quadripunculatus, respectively. Absolute quantification of CY DNA was achieved by comparison with a dilution series of the plasmid containing a CY 16S rDNA target sequence. Absolute quantification of plant and insect DNAs was achieved by comparison with a dilution series of the corresponding DNAs. Quantification of CY DNA in relation to host DNA was finally expressed as genome units (GU) of phytoplasma DNA per nanogram of host (plant or insect) DNA. Relative quantification avoided influences due to different yields during the DNA extraction procedure. The quantity of CY DNA was about 10,000–20,000 GU/ng of plant DNA and about 30,000–50,000 GU/ng of insect DNA. The method described could be used to phytoplasma multiplication and movement in different plant and insect hosts.     

The flexibility in the proline ring couples to the protein backbone

In proteins, the proline ring exists predominantly in two discrete states. However, there is also a small but significant amount of flexibility in the proline ring of high-resolution protein structures. We have found that this side-chain flexibility is coupled to the backbone conformation. To study this coupling, we have developed a model that is simply based on geometric and steric factors and not on energetics. We show that the coupling between phi and chi1 torsions in the proline ring can be described by an analytic equation that was developed by Bricard in 1897, and we describe a computer algorithm that implements the equation. The model predicts the observed coupling very well. The strain in the C(gamma)-C(delta)-N angle appears to be the principal barrier between the UP and DOWN pucker. This strain is relaxed to allow the proline ring to flatten in the rare PLANAR conformation.     

Gene amplification as a developmental strategy: isolation of two developmental amplicons in Drosophila

Gene amplification is known to be critical for upregulating gene expression in a few cases, but the extent to which amplification is utilized in the development of diverse organisms remains unknown. By quantifying genomic DNA hybridization to microarrays to assay gene copy number, we identified two additional developmental amplicons in the follicle cells of the Drosophila ovary. Both amplicons contain genes which, following their amplification, are expressed in the follicle cells, and the expression of three of these genes becomes restricted to specialized follicle cells late in differentiation. Genetic analysis establishes that at least one of these genes, yellow-g, is critical for follicle cell function, because mutations in yellow-g disrupt eggshell integrity. Thus, during follicle cell differentiation the entire genome is overreplicated as the cells become polyploid, and subsequently specific genomic intervals are overreplicated to facilitate gene expression.     

Experimental models linking dendritic cell lineage,phenotype and function

One of the important issues in dendritic cell (DC) biology today is how DC control the fate of T cells. Our data suggest that an important branch point in determining T cell fate is the decision between deletion and memory. We have previously hypothesized that this binary decision is determined by contact with DC derived from lymphoid- versus myeloid-restricted progenitors. However, the false attribution of CD8alpha expression as a reliable marker of lymphoid origin has underpinned a number of studies in which DC expressing CD8alpha did not induce deletion, thereby clouding the issue of whether deletion is indeed a function of lymphoid DC. By returning to basics, that is, functional testing of the progeny of lymphoid- and myeloid-restricted progenitors in vivo, we hope to provide clear evidence of the in vivo roles of lymphoid and myeloid DC subsets, independent of assumptions about the surface phenotypes they can assume.     

Ultrastructural modifications and phosphatidylinositol-3-kinase expression and activity in myocardial tissue deriving from rats in different experimental conditions

Oxygen supply is essential in the maintenance of the physiological cell metabolism. In fact, both lower and higher O2 concentrations induce modifications of the enzymatic activity of the cell which determine, in turn, morphological changes at nuclear and cytoplasmic level. Among the molecules involved in the maintenance of the cellular homeostasis, the signal transduction pathway PI-3-kinase/AKT-1 should be included. Here we suggest a relationship between the modulation of this pathway and the morphological modifications occurring "in vivo" in myocardial tissue upon hypoxic and hyperoxic stress. In particular, down regulation of this pathway, which when activated is known to deliver an anti-apoptotic signal, is concomitant to the maintenance of the apoptotic events occurring in these cells in response to oxidative stresses.