We investigated the effects of gonyautoxins (GTXs) and tetrodotoxin (TTX) on cardiovascular function in 60 adult rabbits following injections of oxprenolol (β-blocker) or oxprenolol (β-blocker) and phentolamine (α-blocker). The effects of GTXs (3.0, 5.0 or 7.0 MU/kg, i. v.) and TTX (5.0, 7.0 or 11.3 MU/kg, i. v.) on cardiovascular function were assessed by measuring the electrocardiogram (ECG) and mean aortic pressure (MAP) changes in anesthetized rabbits. The ECG was monitored with A-B lead and MAP with a cathetertransducer system. In rabbits pretreated with oxprenolol (0.1mg/kg, i. v.), atrioventricular and intraventricular conduction blocks were observed but the same arrhythmia as in the intact animal was not observed after the administration of GTXs, while no remarkable effects of TTX on the cardiac function were apparent in the ECG. In rabbits treated with both phentolamine (0.05mg/kg, i. v.) and oxprenolol (0.1mg/kg, i. v.), ECG findings after the injection of GTXs or TTX were similar to those observed in the animals given only oxprenolol. GTXs induced hypotension whereas TTX had no effect on MAP except at higher dose. These results suggest that TTX depresses the sympathetic cardiac nerves and the arteriolar muscles at higher dose, while GTXs facilitate the sympathetic cardiac nerves but directly depress the cardiac and the arteriolar muscles.
The migration of the carcinogen toluenediamine (TDA), a hydrolysate of toluenediisocyanate (TDI), from polyurethane sheets and prototype urethane-coated tableware was studied. The detection limit of TDI by the colorimetry proposed in the final draft for the Japanese Standards on Plastic Packages and Containers for Foodstuffs was 50ppb, and that by high performance liquid chromatography (HPLC) with a voltammetric detector was 0.2ppb as TDA. Both 2, 4- and 2, 6-TDA were determined separately by HPLC. Recoveries of TDA were from 50 to 82% at the level of 0.5ppb in food-simulating solvents. The highest migration of 2, 4-TDA, 1ppb, was observed when 20% ethanol was used as a food-simulating solvent for polyurethane sheets. When prototype bowls which had been coated with a mixture of excess TDI and other materials and allowed to stand for 3 days at room temperature for hardening were subjected to the migration tests, 0.7ppb of 2, 4- and 0.3ppb of 2, 6-TDA migrated into 20% ethanol. At 10 days after coating, 0.2ppb of 2, 4-TDA migrated from the bowl, but TDA was not detected in 20% ethanol from the bowl coated with a coating material of a standard composition.
Meats and meat products purchased from retail stores were studied to determine the viable counts and isolation rate of Lactobacillus subgenera and the effect of incubation temperature on the isolation of lactobacilli. All the samples of meats, meat products sold by the slice and sausages of home-made type were found to contain lactobacilli, but no more than 23% of the packed meat products were Lactobacillus-positive. After the cut meat samples had been stored at 4°C, the viable counts of streptobacteria increased by about 102-fold to 104-fold as compared with those in the fresh samples, while thermobacteria and betabacteria, with the exception of one sample of the latter, showed no change or even a decrease in counts. Streptobacteria and psychrophilic betabacteria were isolated from some of the meat products with a remarkable increase in counts during storage. Incubation of plates at 37°C was shown to be essential for isolation of thermobacteria and thermophilic betabacteria from meats.
A high performance liquid chromatographic method (HPLC method) for the determination of enramycin in chicken and swine muscles has been developed. The drug was extracted from muscle with hydrochloric acid-acetone, followed by liquid-liquid partition for clean-up. The determination of enramycin was carried out by HPLC with a UV detector set at 230nm, using a Nucleosil 5 C18 column. The calibration curve for enramycin was linear from 20ng to 200ng. Recoveries of enramycin added to chicken and swine muscles at the level of 1.0ppm were 62.4 and 54.0%, respectively. The detection limit was 0.2ppm for both muscles. The relationship between the values obtained by the HPLC method (X) and the bioassay method (Y) could be expressed as follows: Y=0.96X+0.13, correlation coefficient r=0.98.
A simultaneous determination method for residues of three diphenyl ether herbicides (NIP, CNP, X-52) and TPN in vegetables was developed. This method consisted of extraction with acetone and acetonitrile (after addition of 2ml of phosphoric acid), clean-up on a silica gel column and determination by ECD-GC. The average recoveries of these diphenyl ether herbicides and TPN added to vegetables were in the range of 79.0-97.5%. A survey of commercial vegetables by the use of this method revealed levels of TPN of 0.002-0.054ppm in 3 (tomato 2, peas 1) out of 20 samples, but diphenyl ether herbicides were not detected. The sample extracts in which TPN residues were found by GC were also checked by GC-MS.
Benzoic acids of natural origin were found at high concentrations (262.8-635.7ppm) in four samples of Japanese apricot extracts being introduced in the health food market. In view of data from experiments based on the general production method of Japanese apricot extracts, the above benzoic acids were considered to have been derived from amygdalin (a cyanogen glucoside) in the apricot kernel. During the production of Japanese apricot extracts, amygdalin is hydrolyzed even in acidic juice (about pH 3) by β-glucosidase present in the kernel. Amygdalin is transformed to a benzaldehyde when the acidic juice is being obtained by squeezing and filtration. The benzaldehyde is then oxidized to benzoic acid. Cyanic acids were also generated in the hydrolysis, but were easily volatilized and were not present in final juice. All those reactions were completed within the first four hours during processing. The benzaldehyde in the viscid final juice was determined by reverse-phase liquid chromatography after pretreatment. In order to eliminate cyanic and benzoic acids from the final extracts, kernels should not be allowed to remain in contact with the fruit juice during the production process.
A separative determination method for mono-, di- and triisopropyl citrates in foods was developed by gas chromatography (GC). Authentic mono-, di- and triisopropyl citrates were synthesized, purified and used as standard materials. Isopropyl citrates in edible oil were directly dissolved in n-hexane. Isopropyl citrates in butter or milk powder were extracted with ethyl acetate under acidic conditions. In order to separate mono- and diisopropyl citrates, the organic solution was shaken with 5% sodium bicarbonate and then the alkaline aqueous layer was adjusted to pH 1.0 and the isopropyl citrates were reextracted with ethyl acetate. On the other hand, the ethyl acetate containing triisopropyl citrate was evaporated and the residue was taken up in n-hexane, then the triisopropyl citrate in n-hexane was extracted into acetonitrile. After evaporation of the solvent, the mono- and diisopropyl citrates were methylated with diazomethane, then they and the triisopropyl citrate were determined by GC. Recoveries of isopropyl citrates from edible oil, butter and milk powder by this method were more than 91.4%. The detection limits of isopropyl citrates were 1μg/g of sample.
A total of 670 strains of lactobacilli isolated from meat and meat products were physiologically characterized; they fell into 10 groups (433 strains) of streptobacteria, 5 groups (122 strains) of thermobacteria, and 4 groups (115 strains) of betabacteria. On the basis of the number of isolates and positive samples, important groups in meat were S5, S6, S7 (relatively similar to L. curvatus), S8 (similar to L. sake), S10 (L. plantarum), T2 (relatively similar to L. helveticus), T3 (L. crispatus or L. acidophilus), T4 (L. salivarius), B1 (L. fermentum), and T3 (L. brevis); in meat products, significant groups were S5, S8, and B2 (L. viridescens). The isolation of thermobacterial groups and group B1 from meats is discussed in connection with the hygienic condition of the food.
A method for the determination of chlordanes (total of 19 compounds: heptachlor, compound C, compound K, α-chlordene, β-chlordene, γ-chlordene, traps-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor, oxychlordane, heptachlor epoxide, compounds 1, 2, 3, 5, 6, 7 and 8) by mass spectrometry with selected ion monitoring (SIM) was developed. Chlordanes were extracted from samples with organic solvents (e. g. hexane-acetone), partitioned with hexane-acetonitrile, cleaned-up by Florisil column chromatography with a hexane-dichloromethane-ethyl ether solvent system, and determined by SIM. The determination of chlordanes by SIM was carrided out under the following conditions: 1% OV-210+1% OV-275 and 2% OV-210 columns; column temperature, 175-220°C; He, 40ml/min; mainly M-Cl ions; ionization voltage of 27 or 30eV. Recoveries of chlordanes added to samples (water, fish and shellfish, beef and cow's milk) were in the range of 76-102%.
The formation of aflatoxicols (AFL) by 9 strains of Aspergillus flavus isolated from moldy corn, which was naturally contaminated with both aflatoxins (AF) and AFL, and by 2 strains of A. parasiticus from buckwheat flour was investigated. All of the AF-producing A. flavus and A. parasiticus strains showed activity to form both AF and AFL. The accumulation of AF and AFL in three substrata (corn grits, polished rice and peanuts) by an AF-producing strain of A. flavus was investigated. In each substratum, the largest amount of AF was detected at 6 to 10 days' incubation, and the amounts of both AFL A and B rapidly increased thereafter.
A simple and rapid method was developed for the determination of benzoic acid, sorbic acid and dehydroacetic acid in margarine by high performance liquid chromatography (HPLC). A 1.0g sample of margarine in a 50ml centrifuge tube with 50ml of distilled water was warmed to an almost completely molten state, and shaken vigorously. The water layer was taken out and a portion of it was filtered through a 0.45μm pore membrane filter. The filtrate was injected into an HPLC column (4.6×50mm) packed with Unisil Q C18 (5μm). The column was eluted with a mixture of 0.03M sodium acetate-acetic acid buffer (pH 5.0)-methanol (4:1). The preservatives were detected with a UV-spectrophotometer set at 225nm. Average recovery of individual preservatives from margarine was more than 96%. The detection limits were benzoic acid 0.5mg/kg, sorbic acid 0.7mg/kg and dehydroacetic acid 1.0mg/kg. There is no substantial difference in the recoveries from margarine of these preservatives between the proposed method and the steam distillation-GC method.