Tryptophan force-feeding: Changes in the activities of acetylcholinesterase in various tissues of well-fed normal and adrenalectomized rats

The activity of acetylcholinesterase in the liver, heart, spleen, lungs and kidneys of well-fed normal and adrenalectomized rats was measured following a single tube-feeding of tryptophan. In well-fed normal rats, 30 min after tryptophan force-feeding, the enzyme activity in the heart and lungs was stimulated by 28 and 25% as compared to the water-fed control while in well-fed adrenalectomized rats acetylcholinesterase acticity in the heart, liver spleen and lungs was 40, 31, 22 and 15% increased, respectively over that of the corresponding control. In both groups of rats the enzyme activity in the kidney was unaffected by tryptophan. In the liver, spleen and heart of well-fed adrenalectomized rats the pattern of response for acetylcholinesterase to a tryptophan dose, over a period of 24-hr. was found to be biphasic. In well-fed adrenalectomized rats the tryptophan-mediated stimulation of acetylcholinesterase activity in the heart was found to be insensitive to actinomycin-D. The tryptophan-mediated stimulation of acetylcholinesterase activity in the heart of well-fed normal and adrenalectomized rats could not be related to the presence of an activator.     

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.     

A Novel Zeolite Coating for Protection of Concrete Sewers from Biological Sulfuric Acid Attack

Microbial growth inhibition and resistance to biological deterioration of concrete specimens coated with silver-loaded zeolite was evaluated by measuring the time course of bacterial growth, biological sulfur oxidation, and sulfate production using Acidithiobacillus thiooxidans as a corrosive agent. Live bacterial cells declined from an initial inoculum concentration of 1.1 × 10₄ cell ml_-1 to zero in 10 days, during which only 0.5–1% of the initial sulfur concentration of 10 g l_-1 was biologically oxidized, corresponding to sulfate production rates of 35–42 mg SO ₄ ^{2 ?} g ^{? 1} S ^{? 1} . Leaching coefficients of calcium and silicon in the specimens coated with silver-loaded zeolite of 1.6 × 10 ^{? 4} to 4.6 × 10 ^{? 2} cm ² d ^{? 1} respectively, were only 0.8% and 1% of the uncoated specimens.     

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.