Nobuhiko Arakawa

Presence of nitrosable mutagen precursors in cooked meat and fish

Broiled chicken, pork, mutton, beef and sun-dried sardine were found to yield direct-acting mutagenicity after nitrite treatment. When 50% methanol extracts of cooked foods were treated with 50 mM nitrite at pH 3 for 1 h at 37 degrees C, they induced 3800-17,900 revertants of Salmonella typhimurium TA100 and 15,000-43,600 revertants of TA98 per g. In contrast, raw meat and uncooked sun-dried sardine showed little or no mutagenicity after nitrite treatment. Treatment of broiled chicken with 0.5-3 mM nitrite, which is a physiologically feasible concentration in the human stomach under some conditions, induced direct-acting mutagenicity. When broiled chicken was treated with 1 mM nitrite at pH 3 for 1 h at 37 degrees C, its mutagenicities on TA100 and TA98 without S9 mix were 7100 and 5400 revertants/g, respectively.

Detection of mutagenicity of diphenyl ether herbicides in Salmonella typhimurium YG1026 and YG1021

Three kinds of diphenyl ether herbicides, 4-nitrophenyl 2,4,6-trichlorophenyl ether (CNP, chlornitrofen), 2,4-dichlorophenyl 3-methoxy-4-nitrophenyl ether (chlomethoxynil) and 2,4-dichlorophenyl 3-methoxycarbonyl-4-nitrophenyl ether (bifenox), were tested for mutagenicity in Salmonella typhimurium YG1026 and YG1021, which have high nitroreductase activity, and also in S. typhimurium TA100 and TA98. CNP and chlomethoxynil showed mutagenicity in S. typhimurium YG1026, without S9 mix, inducing 50 and 304 revertants per microgram. These mutagenicities were suppressed by the addition of S9 mix. CNP and chlomethoxynil were also mutagenic to YG1021 with and without S9 mix, and their mutagenicities were lower than those to YG1026. On the other hand, bifenox was mutagenic to YG1026 only with S9 mix, inducing 3.0 revertants per micrograms. These three herbicides showed no mutagenicity in S. typhimurium TA100 and TA98 either with or without S9 mix.

Effects of L -Ascorbic Acid on Lysyl Oxidase in the Formation of Collagen Cross-links

To clarify the role of L-ascorbic acid (AsA) in the formation of pyridinoline, we examined the effects of AsA in vitro using soluble collagen and partially purified lysyl oxidase from bovine aorta. The concentration of dehydrodihydroxylysinonorleucine decreased when AsA was added in the early stage of pyridinoline formation. However, when AsA was added in a later stage of pyridinoline formation, the concentration of pyridinoline was not affected. These findings indicated that AsA was involved in the initial enzymatic reaction in pyridinoline synthesis. We purified lysyl oxidase to confirm its association of AsA. AsA inhibited the enzyme activity. Erythorbic acid and 3,4-dihydroxybenzoate suppressed the enzyme activity as well as AsA did. The inhibition by AsA of the lysyl oxidase activity arose from characteristics of AsA structure. AsA might be important in the regulation of the oxidative reaction of lysine.

Sensory evaluation of fish sauces

Abstract Sensory evaluation of anaerobically and aerobically fermented commercial fish sauces was carried out. The results of the evaluation by two groups of Filipinos (A and B) and one group of Japanese (D) revealed a difference in the smell and taste of the fish sauces. However, after several exposures the difference in smell became significantly smaller, but the taste remained almost unchanged. Groups A and B (familiar with aerobically fermented fish sauce) preferred the smell of the aerobic over that of the anaerobic sauce but accepted the taste of the anaerobic sauce. Group D, who had never known or heard of either of the sauces, had a reverse reaction and preferred the anaerobic over that of the aerobic sauce. Group C (Filipino children) did not like the sauces. In general, fermentation under anaerobic conditions brought about changes in the aroma quality of fish sauce during the manufacturing process, to yield an acceptable product.

Sensory acceptance and overall quality of a histidine added fish sauce

Abstract A 4 month incubated histidine added fish sauce wherein the hydrolysis of fish protein was accelerated during the fermentation process, was sensorially evaluated in respect to taste, smell, color and overall quality and compared with the control. Sensory evaluation results showed that the accelerated hydrolysis product fish sauce brought about by the addition of histidine was acceptable in respect to taste, smell, color and overall quality but not the control which was found to be still in the immature stage. A difference between the control and the histidine added sample was confirmed and that the concentrations of volatile acids in the control was higher than the histidine added sample. Panelists who were not familiar with the fish sauce preferred the histidine added sauce over the commercial fish sauces while those who were familiar, preferred the traditionally produced commercial sauce but accepted the histidine added sauce. Addition of histidine during fermentation did not increase the amount of histamine in the fish sauce.

Role of Supplemental Ascorbate on Regulation of Growth in Cultured Cells

L-Ascorbic acid is widely consumed as a dietary supplement with the goal of prophylaxis or treatment for health aberrations. Possible mechanisms of ascorbate (AsA) that alleviate the physiological changes caused by certain life hazards and diseases have been elucidated. AsA is known to act as an anitioxidant and a prooxidant in vitro, but it is thought that the adverse effects induced by high amounts of AsA are unlikely to be important in vivo. In general, the AsA content in tissues decreases with age, and high intake of AsA appears promising for protection against oxidative stress during aging. Here, we review our findings concerning to the effects of AsA on cell growth.

Chemical Studies on the Autolysis of Meats. Part XIII

動物の死直後肉中に存在する遊離アミノ酸及びそれらが肉の熟成(貯蔵)中如何に変化するかをペーパークロマトグラフ法で追求した.豚,鶏,鯉,カツオ,マグロ肉について行った結果は次の如くである. (1)死直後肉中に認められるアミノ酸はグリシン,アラニン,グルタミン酸(鯉肉には認められない)及び.タウリンである. (2)肉中遊離アミノ酸の量及び種類は豚肉,カツオ,マグロ肉に多く,鶏肉,鯉肉に少いなど一般に呈味濃厚と思われる肉に多い傾向がみられる. (3)肉の熟成(貯蔵)中遊離アミノ酸の量及び種類は増加し,死直後認められなかったスレオニン,ロイシン,イソロイシン,フェニルアラニンなどの生じてくるのが認められた.