Polymerization of β-lactoglobulin and bovine serum albumin at oil-water interfaces in emulsions by transglutaminase

Polymerization of β-lactoglobulin and bovine serum albumin at the oil—water interfaces in n-tetradecane-in-water emulsions induced by the transglutaminase reaction was studied. The emulsions were incubated with transglutaminase for various times, and adsorbed and unadsorbed protein fractions at the oil—water interfaces were analyzed by sodium dodecyl sulfate—polyacrylamide gel electrophoresis. While only monomers were detected in the unadsorbed fractions, polymers were observed in the adsorbed fractions of the both proteins. The sizes and amounts of the polymers increased with incubation time. The incubation with transglutaminase caused much flocculation of the emulsion stabilized by β-lactoglobulin. An increase in viscosity was also observed with the flocculation. The flocculation was probably initiated by the formation of ε-(γ-glutamyl)-lysyl isopeptide bonds between β-lactoglobulin molecules adsorbed on different oil droplets. In the case of the emulsion stabilized by bovine serum albumin, however, the flocculation and the increase in viscosity occurred to only limited extents by the transglutaminase reaction. This suggests that ε-(γ-glutamyl)-lysyl isopeptide bonds induced by the transglutaminase reaction were formed only between neighboring molecules of bovine serum albumin on the same droplet.     

Hepatic and serum bile acid compositions in patients with biliary atresia: a microanalysis using gas chromatography-mass spectrometry with negative ion chemical ionization detection

Osteopontin is a bone protein also expressed in other tissues. Increased osteopontin is thought to be associated with tissue inflammation. We used immunocytochemical analyses and polymerase chain reaction amplification of mRNA to examine osteopontin expression and regulation in unilateral ureteral obstruction (UUO) in rats, a model of inflammatory kidney disease. In the obstructed kidney, osteopontin mRNA and protein were significantly increased. The increase reached 4-fold after 1 day of UUO and persisted at this level for the 5-day duration of UUO. Immunocytochemical analyses showed increased osteopontin protein in tubular cells of the obstructed kidney cortex from days 1 through 5 of UUO. No such significant increase was apparent in the glomerulus or interstitium. Increased osteopontin mRNA and protein likewise occurred in the tubular cells of the obstructed kidney of rats that had undergone whole-body irradiation to eliminate macrophage infiltration into the experimental kidney. Purified osteopontin was found to be a chemoattractant for macrophages isolated from the rat peritoneum. Enalapril treatment, which decreases macrophage infiltration of the obstructed kidney, had no effect on the increase in osteopontin mRNA but significantly attenuated the increase in protein in tubular cells. Western blot analysis of whole cortical homogenates revealed that the osteopontin antibody recognized one protein of 67 kD. The amount of this protein was substantially decreased in kidney homogenates obtained from enalapril-treated compared to untreated animals. Increased osteopontin synthesis may, therefore, contribute in part to the inflammatory response that characterizes obstructive nephropathy.     

Effects of Groundwater Table Position and Soil Properties on Stability of Slope during Rainfall

Rainfall, hydrological condition, and geological formation of slope are important contributing factors to slope failures. Parametric studies were carried out to study the effect of groundwater table position, rainfall intensities, and soil properties in affecting slope stability. Three different groundwater table positions corresponding to the wettest, typical, and driest periods in Singapore and four different rainfall intensities (9, 22, 36, and 80 mm/h) were used in the numerical analyses. Typical soil properties of two main residual soils from the Bukit Timah Granite and the sedimentary Jurong Formation in Singapore were incorporated into the numerical analyses. The changes in factor of safety during rainfall were not affected significantly by the groundwater table near the ground surface due to the relatively small changes in matric suction during rainfall. A delay in response of the minimum factor of safety due to rainfall and a slower recovery rate after rainfall were observed in slopes from the sedimentary Jurong Formation as compared to those slopes from the Bukit Timah Granite. Numerical analyses of an actual residual soil slope from the Bukit Timah Granite at Marsiling Road and a residual soil slope from the sedimentary Jurong Formation at Jalan Kukoh show good agreement with the trends observed in the parametric studies.     

Amino Acid Absorption in Portal Blood After Duodenal Infusions of a Soy Protein Hydrolysate Prepared by a Novel Soybean Protease D3

ABSTRACT:  The intestinal absorption of amino acids from decapeptide was investigated in rats under unrestrained conditions. The soy protein hydrolysate utilized in the experiment was produced by a novel soybean protease D3. The enzymatic features of protease D3 showed high homology with cathepsin L and cathepsin K and the average molecular weight of D3 hydrolysate is approximately 1200. We compared the intestinal absorption of D3 hydrolysate in portal blood with that of an amino acids mixture and soy protein with the same amino acid composition by determining the concentration of individual amino acids after a single administration of a nitrogen source. The absorptive velocity and intensity of each amino acid were calculated from its rate of elevation in the portal blood. And in most cases, these were higher in the D3 hydrolysate than in amino acids mixture and protein. The proportion of the amount of each amino acid absorbed in portal blood from D3 hydrolysate was much more like the composition of the administrated amino acids than like that from the amino acids mixture. The result of in vitro digestion assay indicated that D3 hydrolysate was hydrolyzed easier than the hydrolysates produced by microbial proteases. This is the first report to demonstrate that the D3 hydrolysate, which contains decapeptide as a dominant fraction, was more rapidly utilized than the amino acids mixture and protein as is the case with di-, tripeptides. This suggested that this hydrolysate could be available for nutraceutical use as well as use in nutritious foods for athletes and patients.     

Characteristic Property of Low Bitterness in Protein Hydrolysates by a Novel Soybean Protease D3

ABSTRACT:  Enzymatic hydrolysis is 1 means of improving the functional properties of food protein; however, in most cases, bitter peptides are generated by such treatment, and the resulting product is therefore not acceptable as a food ingredient. We have already reported a novel cysteine protease, D3, purified from germinating soybean cotyledons. Because of its substrate specificities, most hydrophobic amino acid residues in the hydrolysate are presumed not to be located at the peptide termini. It was therefore expected that protein hydrolysate by protease D3 would taste less bitter than other enzymatic hydrolysates. The objective of this study was to demonstrate the low bitterness of protein hydrolysates by protease D3. For that purpose, soy protein and casein hydrolysates were prepared with treatment of protease D3, subtilisin, pepsin, trypsin, and thermolysin, respectively. The bitterness of these hydrolysates was evaluated by measuring points of subjective equality (PSE). The PSE value demonstrated that the protein hydrolysates by protease D3 were significantly less bitter than the other enzymatic hydrolysates, indicating that the products had a taste mild enough to be acceptable as a less-bitter peptide food ingredient. These results suggested that a prominent feature of protease D3 was its capacity to produce less-bitter peptides. Therefore, it is thought that protease D3 could be applied to produce protein hydrolysates for use as ingredients in a variety of food products.     

Effects of organophosphates on rabbit pyramidal cells firing pattern and hippocampal theta rhythm

The effects of the irreversible acetylcholinesterase (AChE) antagonist paraoxon (Px) on hippocampal neurophysiology were investigated and compared to those of physostigmine in urethane-anaesthetized rabbits. Hippocampal CA1 EEG signals were analyzed by power spectra. Following intracarotid administration, the two drugs induced a similar fundamental low-frequency theta power peak while the appearance of a second theta harmonic was commonly found under Px. Again, inhibition of CA1 pyramidal cells firing was significantly more pronounced after Px injection than after physostigmine. A potent inhibitory action was also described following local Px iontophoretic application. However, a discrepancy appeared between the effects of Px and the classical cholinergic drugs (acetylcholine, physostigmine). The results indicate that Px and physostigmine have a rather similar influence on the septo-hippocampal pathway and support suggestions that Px could act within local hippocampal circuitry through other systems than the cholinergic system exclusively.     

Comparison of Deamidation Activity of Transglutaminases

ABSTRACT: A comparison was made of the deamidation activity of transglutaminases fro m guinea pig liver (GTGase), fish red sea bream liver (FTGase) and microorganisms (MTGase). Against the Z-Gln-Gly, kinetic constants of the deamidation and incorporation of primary amine were measured. GTGase and FTGase showed similar deamidation activity, however, that of MTGase was less than 1/7 of the other two TGases. Against the proteins, N, N-dimethylated casein and native gliadin, FTGase was the most active and deamidated respectively 45.5% and 38.2% of Gln residues. The deamidation rate of these proteins by GTGase was less than 1/2 and these results were expected to be caused by the difference of substrate specificity of the TGases.     

Role of endogenous hypergastrinemia in regenerating endocrine pancreas after partial pancreatectomy

We studied the possible role of endogenous gastrin in the regenerating pancreas. Male Wistar rats underwent sham operation or 90% partial pancreatectomy (Px). Lansoprazole (30 mg/kg body wt), a proton pump inhibitor (PPI), was given p.o. for 3 weeks after surgery. Plasma glucose levels were higher in Px rats than in shams. Lansoprazole lowered plasma glucose levels in the Px rats. In addition, integrated insulin secretion during an oral glucose tolerance test (2 g/kg body wt) was significantly (p < 0.01) higher in lansoprazole-treated Px rats than in control Px rats, while lansoprazole did not affect insulin secretion in shams. Fasting serum gastrin levels were higher (p < 0.01) in lansoprazole-treated animals than in controls both in sham rats and in Px rats. Furthermore, lansoprazole increased the pancreas weight per body weight and elevated the insulin content of the pancreas in Px rats. These results suggest that endogenous hypergastrinemia has a trophic effect on endocrine pancreas during regenerating processes and that administration of PPI may be clinically beneficial to the remnant pancreas after pancreatectomy if the whole stomach is preserved.