Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Effect of Metalaxyl on the incidence and severity of Pearl millet downy mildew disease in Northern Nigeria

Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight.     

Poly(D,L-lactide-co-glycolide acid) nanoparticles for DNA delivery: waiving preparation complexity and increasing efficiency

When designing a nonviral gene delivery system based on polymeric nanoparticles (NPs), it is important to keep in mind obstacles associated with future clinical applications. Simplifying the procedure of NPs production and taking toxicity into account are the most important issues that need to be addressed. Toxicity concerns in clinical trials may be raised when using additives such as cationic polymers/lipids, buffering reagents, and proteins. Therefore, the aim of this study was to simplify the formulation of poly (lactide-co-glycolide) acid NPs by shortening steps such as sonication time and by avoiding the use of additives while preserving its efficiency. NPs (300 nm) were formulated using a modified w/o/w technique with DNA entrapment efficiency of 80%. Once achieving such NPs, formulation parameters such as DNA loading, release kinetics, DNA integrity and bioactivity, uptake by cells, and toxicity were addressed. The NPs were readily taken by several cell lines and were localized mostly in their endo-lysosomal compartments. The NPs did not affect cells viability. Most importantly, transfection studies in COS-7 and Cf2th cells resulted with a 250-fold protein expression levels when compared with the control. These expression levels are higher than ones achieved with more complicated NPs systems, demonstrating the efficiency of our simplified NPs for gene delivery.     

Effect of temperature on the saccharide composition obtained after alpha-amylolysis of starch

The hydrolysis of starch to low-molecular-weight products (normally characterised by their dextrose equivalent (DE), which is directly related to the number-average molecular mass) was studied at different temperatures. Amylopectin potato starch, lacking amylose, was selected because of its low tendency towards retrogradation at lower temperatures. Bacillus licheniformis alpha-amylase was added to 10% [w/w] gelatinised starch solutions. The hydrolysis experiments were done at 50, 70, and 90 degrees C. Samples were taken at defined DE values and these were analysed with respect to their saccharide composition. At the same DE the oligosaccharide composition depended on the hydrolysis temperature. This implies that at the same net number of bonds hydrolysed by the enzyme, the saccharide composition was different. The hydrolysis temperature also influenced the initial overall molecular-weight distribution. Higher temperatures led to a more homogenous molecular weight distribution. Similar effects were observed for alpha-amylases from other microbial sources such as Bacillus amyloliquefaciens and Bacillus stearothermophilus. Varying the pH (5.1, 6.2, and 7.6) at 70 degrees C did not significantly influence the saccharide composition obtained during B. licheniformis alpha-amylase hydrolysis. The underlying mechanisms for B. licheniformis alpha-amylase were studied using pure linear oligosaccharides, ranging from maltotriose to maltoheptaose as substrates. Activation energies for the hydrolysis of individual oligosaccharides were calculated from Arrhenius plots at 60, 70, 80, and 90 degrees C. Oligosaccharides with a degree of polymerisation exceeding that of the substrate could be detected. The contribution of these oligosaccharides increased as the degree of polymerisation of the substrate decreased and the temperature of hydrolysis increased. The product specificity decreased with increasing temperature of hydrolysis, which led to a more equal distribution between the possible products formed. Calculations with the subsite map as determined for the closely related alpha-amylase from B. amyloliquefaciens reconfirmed this finding of a decreased substrate specificity with increased temperature of hydrolysis. Copyright 1999 John Wiley & Sons, Inc.     

Copper-induced peroxidation of liposomal palmitoyllinoleoylphosphatidylcholine (PLPC), effect of antioxidants and its dependence on the oxidative stress

In an attempt to deepen our understanding of the mechanisms responsible for lipoprotein peroxidation, we have studied the kinetics of copper-induced peroxidation of the polyunsaturated fatty acid residues in model membranes (small, unilamellar liposomes) composed of palmitoyllinoleoylphosphatidylcholine (PLPC). Liposomes were prepared by sonication and exposed to CuCl(2) in the absence or presence of naturally occurring reductants (ascorbic acid (AA) and/or alpha-tocopherol (Toc)) and/or a Cu(I) chelator (bathocuproinedisulfonic acid (BC) or neocuproine (NC)). The resultant oxidation process was monitored by recording the time-dependence of the absorbance at several wavelengths. The observed results reveal that copper-induced peroxidation of PLPC is very slow even at relatively high copper concentrations, but occurs rapidly in the presence of ascorbate, even at sub-micromolar copper concentrations. When added from an ethanolic solution, tocopherol had similar pro-oxidative effects, whereas when introduced into the liposomes by co-sonication tocopherol exhibited a marked antioxidative effect. Under the latter conditions, ascorbate inhibited peroxidation of the tocopherol-containing bilayers possibly by regeneration of tocopherol. Similarly, both ascorbate and tocopherol exhibit antioxidative potency when the PLPC liposomes are exposed to the high oxidative stress imposed by chelated copper, which is more redox-active than free copper. The biological significance of these results has yet to be evaluated.     

N-acyl-homoserine lactone inhibition of rhizobial growth is mediated by two quorum-sensing genes that regulate plasmid transfer

The growth of some strains of Rhizobium leguminosarum bv. viciae is inhibited by N-(3-hydroxy-7-cis tetradecenoyl)-L-homoserine lactone (3OH-C(14:1)-HSL), which was previously known as the small bacteriocin before its characterization as an N-acyl homoserine lactone (AHL). Tn5-induced mutants of R. leguminosarum bv. viciae resistant to 3OH-C(14:1)-HSL were isolated, and mutations in two genes were identified. These genes, bisR and triR, which both encode LuxR-type regulators required for plasmid transfer, were found downstream of an operon containing trb genes involved in the transfer of the symbiotic plasmid pRL1JI. The first gene in this operon is traI, which encodes an AHL synthase, and the trbBCDEJKLFGHI genes were found between traI and bisR. Mutations in bisR, triR, traI, or trbL blocked plasmid transfer. Using gene fusions, it was demonstrated that bisR regulates triR in response to the presence of 3OH-C(14:1)-HSL. In turn, triR is then required for the induction of the traI-trb operon required for plasmid transfer. bisR also represses expression of cinI, which is chromosomally located and determines the level of production of 3OH-C(14:1)-HSL. The cloned bisR and triR genes conferred 3OH-C(14:1)-HSL sensitivity to strains of R. leguminosarum bv. viciae normally resistant to this AHL. Furthermore, bisR and triR made Agrobacterium tumefaciens sensitive to R. leguminosarum bv. viciae strains producing 3OH-C(14:1)-HSL. Analysis of patterns of growth inhibition using mutant strains and synthetic AHLs revealed that maximal growth inhibition required, in addition to 3OH-C(14:1)-HSL, the presence of other AHLs such as N-octanoyl-L-homoserine lactone and/or N-(3-oxo-octanoyl)-L-homoserine lactone. In an attempt to identify the causes of growth inhibition, a strain of R. leguminosarum bv. viciae carrying cloned bisR and triR was treated with an AHL extract containing 3OH-C(14:1)-HSL. N-terminal sequencing of induced proteins revealed one with significant similarity to the protein translation factor Ef-Ts.