Zinc injection into PWR primary coolant in order to reduce radiation buildup has been widely studied, and the reduction effect has been experimentally confirmed. However, some items, such as the optimal concentration of zinc required to reduce radiation buildup, the corrosion control effect of zinc injection, and the influence of zinc injection on the integrity of fuel cladding, have not been clarified yet. In particular, the corrosion suppression effect of zinc remains unconfirmed. Therefore, it is necessary to measure and calculate the solubilities of zinc and nickel spinel oxides, which are formed on the surface of Ni-based alloys in PWR primary systems.In this study, in order to assess the effectiveness of zinc injection in the reduction of radiation buildup and the corrosion control of Ni-based alloy, the potential-pH diagrams for Zn-Cr-H2O, Ni-Cr-H2O and Co-Cr-H2O systems at 573K were constructed and the solubilities of Zn-Cr, Ni-Cr, and Co-Cr spinel oxides were also calculated.It is concluded that under pH conditions for which NiCr2O4 is stable, zinc injection is effective in corrosion control as well as in reducing radiation buildup.

The structures of PF1092A(1), B (2) and C (3), new nonsteroidal progesterone receptor ligands produced by Penicillium oblatum, were elucidated by spectroscopic analyses. These compounds possess an eremophilane-type sesquiterpene carbon skeleton and differ only in that 1 and 2 are different monoacetates of 3. The absolute configurations of 1~3 were determined by single crystal X-ray diffraction analysis of the 4-bromobenzoyl ester of PF1092A and by measuring the optical rotations of the acetylation products of these compounds. PF1092A (1), B (2) and C (3) were isolatedas new progesterone receptor ligands from the mycelia of cultured Penicillium oblatum PF1092. These compounds inhibit [3H]-progesterone binding to the progesterone receptor. In the preceding paper, we described the taxonomy and the fermentation of the producing strain and isolation and the biological activities of these compounds1}. The physico-chemical properties and elucidation of structures of 1, 2 and 3 are presented in this paper.

Reactive oxygen species (ROS), such as hydrogen peroxide (H 2 O 2 ), superoxide anion (O 2 ·Ϫ ) and hydroxyl radicals ( · OH) are produced as an byproduct of many cellular reactions including various metabolic and defense processes. 1,2) ROS produced endogenously may contribute cellular damage during ischemia-reperfusion and inflammation. [3][4][5] It has been demonstrated that H 2 O 2 produce contraction in isolated rabbit aorta, 6) canine coronary, 7) rat pulmonary artery 8) and bovine pulmonary artery 9) and relaxation in pig coronary artery.10) Hydroxylradical contract rat aorta. 11) However, there is few reports that their effects on vasoactive amine-induced contractions. For example, Iesaki et al. reported that H 2 O 2 inhibited phenylephrine-induced contraction. 12)Thus, the present study was designed to test the direct effects of H 2 O 2 or ROS generated by exogenous application of xanthine plus xanthine oxidsae (X/XO) on contraction induced by serotonin (5HT), histamine (His) and acetylcholine (ACh) using isolated porcine coronary arteries. Ethylene diamine tetra-acetic acid (EDTA) to chelate metal ions, which promote the production of ROS, and edaravone, a hydroxyl radical scavenger, 13) were used to clarify the participation of · OH.We found that ROS induced different inhibition to 5HT-, His-and ACh-induced contractions of porcine coronary artery. X/XO treatment caused no inhibition of ACh-induced contraction but inhibited 5HT-and His-induced contractions. And some parts of H 2 O 2 action on porcine coronary artery were different from those of ROS derived from X/XO system. MATERIALS AND METHODS SolutionsThe ionic composition of the Krebs-Henseleite (KH) solution used in the present experiment was as follows (mM): NaCl, 118.4; KCl, 4.7; MgSO 4 , 1.2; KH 2 PO 4 , 1.2; NaHCO 3 , 25.0; CaCl 2 , 2.5; and glucose, 11.1. The solution was continuously bubbled with 95% O 2 and 5% CO 2 (pH 7.4). High K ϩ (124 mM) solution was made by isotonic replacement of NaCl with KCl from KH solution.Tissue Preparation and Contraction Experiment Preparation of isolated porcine coronary artery was essentially similar to the methods previously described.14,15) In briefly, porcine hearts were obtained from a local slaughterhouse and transported to the laboratory immersed in ice-cold oxygenated KH solution. The first branch of the left anterior descending coronary artery was dissected and cleaned of all surrounding fat and connective tissue and was cut into rings of 2-3 mm in length. Vascular rings were mounted on two stainless-steel hooks inserted through the lumen of the ring. The bottom hook in each preparation was fixed, whereas the top hook was attached to a force transducer (T7-30-240, Orientec, Japan) mounted on a movable platform, which allowed adjustment of resting tension. Tension changes were recorded on a recorder (Rikadenki Kogyo Co. Ltd., Tokyo, Japan). Each ring was suspended in a 10 ml organ bath and immersed in KH solution maintained at 37°C. The ring was allowed to equilibrate for 60-90 min with an optimal res...