Optimization of microwave-assisted transesterification of dry algal biomass using response surface methodology

The effect of microwave irradiation on the simultaneous extraction and transesterification (in situ transesterification) of dry algal biomass to biodiesel was investigated. A high degree of oil/lipid extraction from dry algal biomass and an efficient conversion of the oils/lipids to biodiesel were demonstrated in a set of well-designed experimental runs. A response surface methodology (RSM) was used to analyze the influence of the process variables (dry algae to methanol (wt/vol) ratio, catalyst concentration, and reaction time) on the fatty acid methyl ester conversion. Based on the experimental results and RSM analysis, the optimal conditions for this process were determined as: dry algae to methanol (wt/vol) ratio of around 1:12, catalyst concentration about 2 wt.%, and reaction time of 4 min. The algal biodiesel samples were analyzed with GC-MS and thin layer chromatography (TLC) methods. Transmission electron microscopy (TEM) images of the algal biomass samples before and after the extraction/transesterification reaction are also presented.     

The Polysaccharide Capsule of Streptococcus pneumonia Partially Impedes MyD88-Mediated Immunity during Pneumonia in Mice

Toll-like receptors (TLR) and the downstream adaptor protein MyD88 are considered crucial for protective immunity during bacterial infections. Streptococcus (S.) pneumoniae is a human respiratory pathogen and a large majority of clinical pneumococcal isolates expresses an external polysaccharide capsule. We here sought to determine the role of pneumococcal capsule in MyD88-mediated antibacterial defense during S. pneumonia pneumonia. Wild type (WT) and Myd88^-/- mice were inoculated intranasally with serotype 2 S. pneumoniae D39 or with an isogenic capsule locus deletion mutant (D39∆cps), and analysed for bacterial outgrowth and inflammatory responses in the lung. As compared to WT mice, Myd88^-/- mice infected with D39 demonstrated a modestly impaired bacterial clearance accompanied by decreased inflammatory responses in the lung. Strikingly, while WT mice rapidly cleared D39∆cps, Myd88^-/- mice showed 10⁵-fold higher bacterial burdens in their lungs and dissemination to blood 24 hours after infection. These data suggest that the pneumococcal capsule impairs recognition of TLR ligands expressed by S. pneumoniae and thereby partially impedes MyD88-mediated antibacterial defense.     

Constitutive expression of insulin-like growth factor 1 and insulin-like growth factor 1 receptor abrogates all requirements for exogenous growth factors.

BALB/c3T3 cells are exquisitely growth regulated and require both platelet-derived growth factor and insulin-like growth factor-1 (IGF-1) for optimal proliferation. BALB/c3T3 cells that constitutively express IGF-1 and elevated levels of IGF-1 receptor (IGF-1R) are capable of growth in serum-free medium without the addition of any exogenous growth factors. BALB/c3T3 cells overexpressing only the IGF-1R plasmid required IGF-1 or insulin for serum-free growth. Antisense oligodeoxynucleotides complementary to IGF-1R mRNA inhibited IGF-1-mediated cell growth. Under these conditions, neither the epidermal growth factor receptor nor phospholipase C gamma 1 was autophosphorylated. These findings indicate that constitutive expression of IGF-1 and IGF-1R allows 3T3 cells to grow in serum-free medium without addition of those exogenous growth factors that are required by the parent cell line.     

The SH2 and SH3 domain-containing protein GRB2 links receptor tyrosine kinases to ras signaling.

A cDNA clone encoding a novel, widely expressed protein (called growth factor receptor-bound protein 2 or GRB2) containing one src homology 2 (SH2) domain and two SH3 domains was isolated. Immunoblotting experiments indicate that GRB2 associates with tyrosine-phosphorylated epidermal growth factor receptors (EGFRs) and platelet-derived growth factor receptors (PDGFRs) via its SH2 domain. Interestingly, GRB2 exhibits striking structural and functional homology to the C. elegans protein sem-5. It has been shown that sem-5 and two other genes called let-23 (EGFR like) and let-60 (ras like) lie along the same signal transduction pathway controlling C. elegans vulval induction. To examine whether GRB2 is also a component of ras signaling in mammalian cells, microinjection studies were performed. While injection of GRB2 or H-ras proteins alone into quiescent rat fibroblasts did not have mitogenic effect, microinjection of GRB2 together with H-ras protein stimulated DNA synthesis. These results suggest that GRB2/sem-5 plays a crucial role in a highly conserved mechanism for growth factor control of ras signaling.     

The Xmrk receptor tyrosine kinase is activated in Xiphophorus malignant melanoma.

Xmrk encodes a putative transmembrane glycoprotein of the tyrosine kinase family and is a melanoma-inducing gene in Xiphophorus. We attempted to investigate the biological function of the putative Xmrk receptor by characterizing its signalling properties. Since a potential ligand for Xmrk has not yet been identified, it has been difficult to analyse the biochemical properties and biological function of this cell surface protein. In an approach towards such analyses, the Xmrk extracellular domain was replaced by the closely related ligand-binding domain sequences of the human epidermal growth factor receptor (HER) and the ligand-induced activity of the chimeric HER-Xmrk protein was examined. We show that the Xmrk protein is a functional receptor tyrosine kinase, is highly active in malignant melanoma and displays a constitutive autophosphorylation activity possibly due to an activating mutation in its extracellular or transmembrane domain. In the focus formation assay the HER-Xmrk chimera is a potent transforming protein equivalent to other tyrosine kinase oncoproteins.     

Ecology and management of mahogany (Swietenia macrophylla King) in the Chimanes Forest, Bed, Bolivia

Mahogany ( Swietenia macrophylla King) regenerates in areas of erosion on high terraces and in forest killed by flooding and deposition of alluvial sediments in the Chimanes Forest, Bolivia. These hydrological disturbances are patchy, and only one of five stands of mahogany that we inventoried was regenerating. Mahogany survives these disturbances significantly better than the common tree species. The long time between disturbances appears to favour late maturation. Mahogany trees allocate little photosynthates to reproduction until they are very large emergents, at least 80 cm in diameter. The episodic nature of the regeneration sites means that mahogany stands are composed of one or a few cohorts, which are vulnerable to overharvesting, particularly with the current use of a minimum cutting diameter to regulate harvest. The delayed onset of fecundity means that the small trees that escape harvest are not very fecund, resulting in minimal seed input to logged forest. Only 7–9% of the gaps created by logging contain natural regeneration after 20 + yr. A successful management plan for mahogany would entail a monocyclic harvest, with a rotation age of 100 + years, the estimated time that it takes for trees to achieve commercial size in natural forest. Since the number of seed trees that will be left is small, they should be concentrated in sites that are likely to be conducive to natural regeneration, such as near rivers and flood damaged forest. Seed production will be maximized for a given basal area (opportunity cost to loggers) if trees c. 110 cm dbh are selected as seed trees. The mahogany stocks in the Chimanes Forest are nearly exhausted, but the findings of this study could be used to help rebuild the mahogany populations, or to design management plans for the commercial species that have similar ecologies to mahogany.     

Capsaicin-induced bronchodilation in mild asthmatic subjects: possible role of nonadrenergic inhibitory system

We investigated whether stimulation of vagal afferent nerve fibers with inhaled capsaicin could induce a nonadrenergic inhibitory reflex in nine mild asthmatic subjects. Changes in total respiratory resistance (Rrs) were measured with a forced oscillation technique. First we induced a rise of 71 +/- 15% in Rrs (P less than 0.001) after leukotriene D4 aerosol. Subsequent inhalation of capsaicin (2 nmol) caused no significant change in mean Rrs of -1.1 +/- 8.2%. After the muscarinic receptor antagonist ipratropium bromide (120 micrograms) was inhaled, leukotriene D4 increased Rrs by 103 +/- 9% (P less than 0.001). Capsaicin subsequently caused bronchodilation in all subjects (Rrs = -22.3 +/- 2.7%, P less than 0.001). Ethanol-saline (diluent) alone caused a nonsignificant fall in Rrs (-9.9 +/- 4.7%) but a deep breath and coughing resulted in bronchodilation (-16.9 +/- 6.1%, P less than 0.05 and -11.6 +/- 2.9%, P less than 0.01, respectively). As observed in normal subjects, capsaicin may initiate an inhibitory reflex, presumably of nonadrenergic origin. This reflex could not be distinguished from that caused by coughing or by deep inhalation. A defect in nonadrenergic mechanisms, at least in mild asthma, seems unlikely.